<!-- activity_main.xml -->
<layout xmlns:android="http://schemas.android.com/apk/res/android"><!-- 数据声明部分 --><data><!-- 声明一个User类型的变量，名称为user --><variablename="user"type="com.example.User" /><!-- 声明一个字符串类型的变量，名称为message --><variablename="message"type="String" /><!-- 声明一个可观察的Boolean类型变量，名称为isLoading --><variablename="isLoading"type="androidx.lifecycle.MutableLiveData<Boolean">>" /></data><!-- 布局内容 --><LinearLayoutandroid:layout_width="match_parent"android:layout_height="match_parent"android:orientation="vertical"><TextViewandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:text="@{user.name}" /> <!-- 使用Binding表达式绑定user变量的name属性 --><TextViewandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:text="@{message}" /> <!-- 使用Binding表达式绑定message变量 --><ProgressBarandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:visibility="@{isLoading ? View.VISIBLE : View.GONE}" /> <!-- 使用Binding表达式绑定isLoading变量 --></LinearLayout>
</layout>

// 变量信息类，用于存储变量的名称、类型等信息
public class VariableInfo {private final String name;        // 变量名称private final String type;        // 变量类型private String defaultValue;      // 变量默认值（可选）private boolean nullable;         // 变量是否可为空public VariableInfo(String name, String type) {this.name = name;this.type = type;}// 获取变量名称public String getName() {return name;}// 获取变量类型public String getType() {return type;}// 设置和获取默认值public void setDefaultValue(String defaultValue) {this.defaultValue = defaultValue;}public String getDefaultValue() {return defaultValue;}// 设置和获取是否可为空public void setNullable(boolean nullable) {this.nullable = nullable;}public boolean isNullable() {return nullable;}
}

// 布局文件解析器的简化实现
public class LayoutFileParser {// 解析布局文件中的数据变量声明public List<VariableInfo> parseVariables(XmlPullParser parser) throws XmlPullParserException, IOException {List<VariableInfo> variables = new ArrayList<>();// 查找data标签int eventType = parser.getEventType();while (eventType != XmlPullParser.END_DOCUMENT) {if (eventType == XmlPullParser.START_TAG && "data".equals(parser.getName())) {// 解析data标签内的内容variables = parseDataTag(parser);break;}eventType = parser.next();}return variables;}// 解析data标签内的内容private List<VariableInfo> parseDataTag(XmlPullParser parser) throws XmlPullParserException, IOException {List<VariableInfo> variables = new ArrayList<>();int eventType = parser.getEventType();while (eventType != XmlPullParser.END_DOCUMENT) {if (eventType == XmlPullParser.START_TAG && "variable".equals(parser.getName())) {// 解析variable标签VariableInfo variable = parseVariableTag(parser);variables.add(variable);} else if (eventType == XmlPullParser.END_TAG && "data".equals(parser.getName())) {break;}eventType = parser.next();}return variables;}// 解析variable标签private VariableInfo parseVariableTag(XmlPullParser parser) {// 获取name和type属性String name = parser.getAttributeValue(null, "name");String type = parser.getAttributeValue(null, "type");// 创建变量信息对象VariableInfo variable = new VariableInfo(name, type);// 处理其他可选属性String defaultValue = parser.getAttributeValue(null, "default");if (defaultValue != null) {variable.setDefaultValue(defaultValue);}String nullable = parser.getAttributeValue(null, "nullable");if (nullable != null) {variable.setNullable(Boolean.parseBoolean(nullable));}return variable;}
}

<!-- 布局文件中声明原生数据类型变量 -->
<data><variablename="count"type="int" /><variablename="price"type="float" /><variablename="isEnabled"type="boolean" />
</data>

// 生成的Binding类中对原生数据类型的处理
public class ActivityMainBinding extends ViewDataBinding {@Nullableprivate int count;         // 整型变量@Nullableprivate float price;       // 浮点型变量@Nullableprivate boolean isEnabled; // 布尔型变量// 设置count变量的方法public void setCount(int count) {this.count = count;notifyPropertyChanged(BR.count);invalidateAll();}// 获取count变量的方法public int getCount() {return count;}// 设置price变量的方法public void setPrice(float price) {this.price = price;notifyPropertyChanged(BR.price);invalidateAll();}// 获取price变量的方法public float getPrice() {return price;}// 设置isEnabled变量的方法public void setIsEnabled(boolean isEnabled) {this.isEnabled = isEnabled;notifyPropertyChanged(BR.isEnabled);invalidateAll();}// 获取isEnabled变量的方法public boolean getIsEnabled() {return isEnabled;}
}

<!-- 布局文件中声明包装数据类型变量 -->
<data><variablename="age"type="java.lang.Integer" /><variablename="total"type="java.lang.Double" /><variablename="visible"type="java.lang.Boolean" />
</data>

// 生成的Binding类中对包装数据类型的处理
public class ActivityMainBinding extends ViewDataBinding {@Nullableprivate Integer age;      // 整型包装类变量@Nullableprivate Double total;     // 双精度浮点型包装类变量@Nullableprivate Boolean visible;  // 布尔型包装类变量// 设置age变量的方法public void setAge(Integer age) {this.age = age;notifyPropertyChanged(BR.age);invalidateAll();}// 获取age变量的方法public Integer getAge() {return age;}// 设置total变量的方法public void setTotal(Double total) {this.total = total;notifyPropertyChanged(BR.total);invalidateAll();}// 获取total变量的方法public Double getTotal() {return total;}// 设置visible变量的方法public void setVisible(Boolean visible) {this.visible = visible;notifyPropertyChanged(BR.visible);invalidateAll();}// 获取visible变量的方法public Boolean getVisible() {return visible;}
}

<!-- 布局文件中声明字符串类型变量 -->
<data><variablename="username"type="java.lang.String" /><variablename="email"type="String" /> <!-- 可以省略包名 -->
</data>

// 生成的Binding类中对字符串类型的处理
public class ActivityMainBinding extends ViewDataBinding {@Nullableprivate String username;  // 字符串变量@Nullableprivate String email;     // 字符串变量// 设置username变量的方法public void setUsername(String username) {this.username = username;notifyPropertyChanged(BR.username);invalidateAll();}// 获取username变量的方法public String getUsername() {return username;}// 设置email变量的方法public void setEmail(String email) {this.email = email;notifyPropertyChanged(BR.email);invalidateAll();}// 获取email变量的方法public String getEmail() {return email;}
}

// 自定义User类
public class User {private String name;  // 用户姓名private int age;      // 用户年龄public User(String name, int age) {this.name = name;this.age = age;}// 获取姓名public String getName() {return name;}// 设置姓名public void setName(String name) {this.name = name;}// 获取年龄public int getAge() {return age;}// 设置年龄public void setAge(int age) {this.age = age;}
}

<!-- 布局文件中声明自定义对象类型变量 -->
<data><variablename="user"type="com.example.User" />
</data>

// 生成的Binding类中对自定义对象类型的处理
public class ActivityMainBinding extends ViewDataBinding {@Nullableprivate User user;  // 自定义User对象变量// 设置user变量的方法public void setUser(User user) {this.user = user;notifyPropertyChanged(BR.user);invalidateAll();}// 获取user变量的方法public User getUser() {return user;}// 执行绑定操作的方法@Overrideprotected void executeBindings() {super.executeBindings();User userValue = user;String nameValue = null;int ageValue = 0;if (userValue != null) {// 获取User对象的属性值nameValue = userValue.getName();ageValue = userValue.getAge();}// 更新视图textViewName.setText(nameValue);textViewAge.setText(String.valueOf(ageValue));}
}

<!-- 布局文件中声明集合类型变量 -->
<data><!-- List集合变量 --><variablename="userList"type="java.util.List<com.example.User">>" /><!-- Map集合变量 --><variablename="userMap"type="java.util.Map<String, com.example.User">>" /><!-- Set集合变量 --><variablename="userSet"type="java.util.Set<com.example.User">>" />
</data>

// 生成的Binding类中对集合类型的处理
public class ActivityMainBinding extends ViewDataBinding {@Nullableprivate List<User> userList;  // List集合变量@Nullableprivate Map<String, User> userMap;  // Map集合变量@Nullableprivate Set<User> userSet;  // Set集合变量// 设置userList变量的方法public void setUserList(List<User> userList) {this.userList = userList;notifyPropertyChanged(BR.userList);invalidateAll();}// 获取userList变量的方法public List<User> getUserList() {return userList;}// 设置userMap变量的方法public void setUserMap(Map<String, User> userMap) {this.userMap = userMap;notifyPropertyChanged(BR.userMap);invalidateAll();}// 获取userMap变量的方法public Map<String, User> getUserMap() {return userMap;}// 设置userSet变量的方法public void setUserSet(Set<User> userSet) {this.userSet = userSet;notifyPropertyChanged(BR.userSet);invalidateAll();}// 获取userSet变量的方法public Set<User> getUserSet() {return userSet;}
}

<!-- 布局文件中声明数组类型变量 -->
<data><!-- 整型数组变量 --><variablename="intArray"type="int[]" /><!-- 字符串数组变量 --><variablename="stringArray"type="java.lang.String[]" /><!-- 对象数组变量 --><variablename="userArray"type="com.example.User[]" />
</data>

// 生成的Binding类中对数组类型的处理
public class ActivityMainBinding extends ViewDataBinding {@Nullableprivate int[] intArray;  // 整型数组变量@Nullableprivate String[] stringArray;  // 字符串数组变量@Nullableprivate User[] userArray;  // 对象数组变量// 设置intArray变量的方法public void setIntArray(int[] intArray) {this.intArray = intArray;notifyPropertyChanged(BR.intArray);invalidateAll();}// 获取intArray变量的方法public int[] getIntArray() {return intArray;}// 设置stringArray变量的方法public void setStringArray(String[] stringArray) {this.stringArray = stringArray;notifyPropertyChanged(BR.stringArray);invalidateAll();}// 获取stringArray变量的方法public String[] getStringArray() {return stringArray;}// 设置userArray变量的方法public void setUserArray(User[] userArray) {this.userArray = userArray;notifyPropertyChanged(BR.userArray);invalidateAll();}// 获取userArray变量的方法public User[] getUserArray() {return userArray;}
}

// 实现Observable接口的User类
public class User implements Observable {private String name;  // 用户姓名private int age;      // 用户年龄// 监听器列表private final PropertyChangeRegistry listeners = new PropertyChangeRegistry();public User(String name, int age) {this.name = name;this.age = age;}// 获取姓名public String getName() {return name;}// 设置姓名，并通知监听器public void setName(String name) {this.name = name;listeners.notifyChange(this, BR.name);}// 获取年龄public int getAge() {return age;}// 设置年龄，并通知监听器public void setAge(int age) {this.age = age;listeners.notifyChange(this, BR.age);}// 添加监听器@Overridepublic void addOnPropertyChangedCallback(OnPropertyChangedCallback callback) {listeners.add(callback);}// 移除监听器@Overridepublic void removeOnPropertyChangedCallback(OnPropertyChangedCallback callback) {listeners.remove(callback);}
}

// 生成的Binding类中对Observable对象的处理
public class ActivityMainBinding extends ViewDataBinding {@Nullableprivate User user;  // 实现了Observable接口的User对象// 用于监听User对象属性变化的回调private final OnPropertyChangedCallback userCallback = new OnPropertyChangedCallback() {@Overridepublic void onPropertyChanged(Observable sender, int propertyId) {// 当User对象的属性发生变化时，触发绑定更新invalidateAll();}};// 设置user变量的方法public void setUser(User user) {// 如果已有User对象，先移除监听器if (this.user != null) {this.user.removeOnPropertyChangedCallback(userCallback);}this.user = user;// 如果新的User对象不为空，添加监听器if (user != null) {user.addOnPropertyChangedCallback(userCallback);}notifyPropertyChanged(BR.user);invalidateAll();}// 获取user变量的方法public User getUser() {return user;}
}

// 使用ObservableField的User类
public class User {public final ObservableField<String> name = new ObservableField<>();  // 可观察的姓名public final ObservableInt age = new ObservableInt();  // 可观察的年龄public User(String name, int age) {this.name.set(name);this.age.set(age);}
}

// 生成的Binding类中对ObservableField的处理
public class ActivityMainBinding extends ViewDataBinding {@Nullableprivate User user;  // 使用ObservableField的User对象// 用于监听name属性变化的回调private final Observable.OnPropertyChangedCallback nameCallback = new Observable.OnPropertyChangedCallback() {@Overridepublic void onPropertyChanged(Observable sender, int propertyId) {// 当name属性发生变化时，触发绑定更新invalidateAll();}};// 用于监听age属性变化的回调private final Observable.OnPropertyChangedCallback ageCallback = new Observable.OnPropertyChangedCallback() {@Overridepublic void onPropertyChanged(Observable sender, int propertyId) {// 当age属性发生变化时，触发绑定更新invalidateAll();}};// 设置user变量的方法public void setUser(User user) {// 如果已有User对象，先移除监听器if (this.user != null) {if (this.user.name != null) {this.user.name.removeOnPropertyChangedCallback(nameCallback);}if (this.user.age != null) {this.user.age.removeOnPropertyChangedCallback(ageCallback);}}this.user = user;// 如果新的User对象不为空，添加监听器if (user != null) {if (user.name != null) {user.name.addOnPropertyChangedCallback(nameCallback);}if (user.age != null) {user.age.addOnPropertyChangedCallback(ageCallback);}}notifyPropertyChanged(BR.user);invalidateAll();}// 获取user变量的方法public User getUser() {return user;}
}

// 使用LiveData的ViewModel
public class MyViewModel extends ViewModel {private MutableLiveData<User> userLiveData = new MutableLiveData<>();  // 可观察的User对象public MyViewModel() {// 初始化User对象User user = new User("John", 25);userLiveData.setValue(user);}// 获取User的LiveDatapublic LiveData<User> getUser() {return userLiveData;}// 更新User对象public void updateUser(User user) {userLiveData.setValue(user);}
}

<!-- 布局文件中声明LiveData变量 -->
<data><variablename="viewModel"type="com.example.MyViewModel" />
</data><LinearLayoutandroid:layout_width="match_parent"android:layout_height="match_parent"android:orientation="vertical"><TextViewandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:text="@{viewModel.user.name}" /><TextViewandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:text="@{String.valueOf(viewModel.user.age)}" />
</LinearLayout>

// 生成的Binding类中对LiveData的处理
public class ActivityMainBinding extends ViewDataBinding {@Nullableprivate MyViewModel viewModel;  // ViewModel对象// 用于观察LiveData变化的观察者private Observer<User> userObserver;// 设置viewModel变量的方法public void setViewModel(@Nullable MyViewModel viewModel) {this.viewModel = viewModel;// 如果已有观察者，先移除if (userObserver != null) {if (this.viewModel != null && this.viewModel.getUser() != null) {this.viewModel.getUser().removeObserver(userObserver);}}// 创建新的观察者userObserver = new Observer<User>() {@Overridepublic void onChanged(@Nullable User user) {// 当LiveData中的User对象发生变化时，触发绑定更新invalidateAll();}};// 如果ViewModel和User的LiveData不为空，添加观察者if (viewModel != null && viewModel.getUser() != null) {viewModel.getUser().observeForever(userObserver);}notifyPropertyChanged(BR.viewModel);invalidateAll();}// 获取viewModel变量的方法public MyViewModel getViewModel() {return viewModel;}
}

<!-- 布局文件中声明泛型类型变量 -->
<data><!-- 泛型List变量 --><variablename="userList"type="java.util.List<com.example.User">>" /><!-- 泛型Map变量 --><variablename="userMap"type="java.util.Map<String, com.example.User">>" /><!-- 自定义泛型类型变量 --><variablename="result"type="com.example.Result<java.lang.String">>" />
</data>

// 自定义泛型类
public class Result<T> {private T data;  // 泛型数据private boolean success;  // 是否成功public Result(T data, boolean success) {this.data = data;this.success = success;}// 获取数据public T getData() {return data;}// 设置数据public void setData(T data) {this.data = data;}// 判断是否成功public boolean isSuccess() {return success;}// 设置是否成功public void setSuccess(boolean success) {this.success = success;}
}

// 生成的Binding类中对泛型类型的处理
public class ActivityMainBinding extends ViewDataBinding {@Nullableprivate List<User> userList;  // 泛型List变量@Nullableprivate Map<String, User> userMap;  // 泛型Map变量@Nullableprivate Result<String> result;  // 自定义泛型类型变量// 设置userList变量的方法public void setUserList(List<User> userList) {this.userList = userList;notifyPropertyChanged(BR.userList);invalidateAll();}// 获取userList变量的方法public List<User> getUserList() {return userList;}// 设置userMap变量的方法public void setUserMap(Map<String, User> userMap) {this.userMap = userMap;notifyPropertyChanged(BR.userMap);invalidateAll();}// 获取userMap变量的方法public Map<String, User> getUserMap() {return userMap;}// 设置result变量的方法public void setResult(Result<String> result) {this.result = result;notifyPropertyChanged(BR.result);invalidateAll();}// 获取result变量的方法public Result<String> getResult() {return result;}
}

// 类型转换器示例
public class Converters {// 将Integer转换为String@BindingConversionpublic static String integerToString(Integer value) {return value == null ? "" : String.valueOf(value);}// 将Boolean转换为可见性@BindingConversionpublic static int booleanToVisibility(Boolean value) {return value == null || !value ? View.GONE : View.VISIBLE;}// 将日期转换为字符串@BindingConversionpublic static String dateToString(Date date) {if (date == null) {return "";}SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");return format.format(date);}
}

<!-- 在布局文件中使用类型转换器 -->
<data><import type="com.example.Converters" /><variablename="age"type="java.lang.Integer" /><variablename="isVisible"type="java.lang.Boolean" /><variablename="birthday"type="java.util.Date" />
</data><LinearLayoutandroid:layout_width="match_parent"android:layout_height="match_parent"android:orientation="vertical"><TextViewandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:text="@{age}" /> <!-- 自动将Integer转换为String --><Viewandroid:layout_width="match_parent"android:layout_height="1dp"android:visibility="@{isVisible}" /> <!-- 自动将Boolean转换为可见性 --><TextViewandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:text="@{birthday}" /> <!-- 自动将Date转换为String -->
</LinearLayout>

// 生成的Binding类中对类型转换的处理
public class ActivityMainBinding extends ViewDataBinding {@Nullableprivate Integer age;  // 整型变量@Nullableprivate Boolean isVisible;  // 布尔型变量@Nullableprivate Date birthday;  // 日期型变量// 执行绑定操作的方法@Overrideprotected void executeBindings() {super.executeBindings();Integer ageValue = age;Boolean isVisibleValue = isVisible;Date birthdayValue = birthday;String ageString = null;int visibility = View.GONE;String birthdayString = null;// 应用类型转换ageString = Converters.integerToString(ageValue);visibility = Converters.booleanToVisibility(isVisibleValue);birthdayString = Converters.dateToString(birthdayValue);// 更新视图textViewAge.setText(ageString);viewSeparator.setVisibility(visibility);textViewBirthday.setText(birthdayString);}
}

// 自定义类型转换器
public class CustomConverters {// 将User对象转换为显示名称@BindingConversionpublic static String userToDisplayName(User user) {if (user == null) {return "";}return user.getName() + " (" + user.getAge() + ")";}// 将Color对象转换为int颜色值@BindingConversionpublic static int colorToInt(Color color) {if (color == null) {return Color.BLACK;}return color.toArgb();}
}

<!-- 在布局文件中使用自定义类型转换器 -->
<data><import type="com.example.CustomConverters" /><variablename="user"type="com.example.User" /><variablename="textColor"type="androidx.compose.ui.graphics.Color" />
</data><LinearLayoutandroid:layout_width="match_parent"android:layout_height="match_parent"android:orientation="vertical"><TextViewandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:text="@{user}" /> <!-- 自动将User转换为显示名称 --><TextViewandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:text="Hello World"android:textColor="@{textColor}" /> <!-- 自动将Color转换为int颜色值 -->
</LinearLayout>

// 生成的Binding类中对自定义类型转换的处理
public class ActivityMainBinding extends ViewDataBinding {@Nullableprivate User user;  // User对象变量@Nullableprivate Color textColor;  // Color对象变量// 执行绑定操作的方法@Overrideprotected void executeBindings() {super.executeBindings();User userValue = user;Color textColorValue = textColor;String displayName = null;int colorInt = Color.BLACK;// 应用自定义类型转换displayName = CustomConverters.userToDisplayName(userValue);colorInt = CustomConverters.colorToInt(textColorValue);// 更新视图textViewUser.setText(displayName);textViewHelloWorld.setTextColor(colorInt);}
}

<!-- 布局文件中设置变量默认值 -->
<data><variablename="count"type="int"default="0" /> <!-- 整型默认值 --><variablename="name"type="String"default="`Unknown`" /> <!-- 字符串默认值，注意使用反引号 --><variablename="isEnabled"type="boolean"default="true" /> <!-- 布尔型默认值 -->
</data>

// 生成的Binding类中对默认值的处理
public class ActivityMainBinding extends ViewDataBinding {private int count = 0;  // 初始化默认值@Nullableprivate String name = "Unknown";  // 初始化默认值private boolean isEnabled = true;  // 初始化默认值// 设置count变量的方法public void setCount(int count) {this.count = count;notifyPropertyChanged(BR.count);invalidateAll();}// 获取count变量的方法public int getCount() {return count;}// 设置name变量的方法public void setName(@Nullable String name) {this.name = name;notifyPropertyChanged(BR.name);invalidateAll();}// 获取name变量的方法public String getName() {return name;}// 设置isEnabled变量的方法public void setIsEnabled(boolean isEnabled) {this.isEnabled = isEnabled;notifyPropertyChanged(BR.isEnabled);invalidateAll();}// 获取isEnabled变量的方法public boolean getIsEnabled() {return isEnabled;}
}

<!-- 布局文件中的空安全处理 -->
<data><variablename="user"type="com.example.User" />
</data><LinearLayoutandroid:layout_width="match_parent"android:layout_height="match_parent"android:orientation="vertical"><!-- 使用安全调用操作符 --><TextViewandroid

<!-- 使用安全调用操作符 --><TextViewandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:text="@{user?.name}" /> <!-- 安全调用操作符，当user为null时返回null --><!-- 使用Elvis操作符提供默认值 --><TextViewandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:text="@{user?.name ?: `Unknown`}" /> <!-- 当user或name为null时使用默认值"Unknown" --><!-- 嵌套安全调用 --><TextViewandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:text="@{user?.address?.city ?: `City Unknown`}" /> <!-- 多级安全调用 -->
</LinearLayout>

// 生成的Binding类中对空安全的处理
public class ActivityMainBinding extends ViewDataBinding {@Nullableprivate User user;  // User对象变量// 执行绑定操作的方法@Overrideprotected void executeBindings() {super.executeBindings();User userValue = user;String nameValue = null;String cityValue = null;// 安全调用操作符的实现if (userValue != null) {nameValue = userValue.getName();}// Elvis操作符的实现String displayName = nameValue != null ? nameValue : "Unknown";// 嵌套安全调用的实现Address address = userValue != null ? userValue.getAddress() : null;cityValue = address != null ? address.getCity() : "City Unknown";// 更新视图textViewName.setText(displayName);textViewCity.setText(cityValue);}
}

<!-- 布局文件中声明可为空的变量 -->
<data><!-- 明确声明可为空的变量 --><variablename="nullableUser"type="com.example.User"nullable="true" /><!-- 默认为不可为空的变量 --><variablename="nonNullUser"type="com.example.User" />
</data>

// 生成的Binding类中对可为空性的处理
public class ActivityMainBinding extends ViewDataBinding {@Nullableprivate User nullableUser;  // 明确可为空的变量@NonNullprivate User nonNullUser;  // 默认为不可为空的变量// 设置nullableUser变量的方法public void setNullableUser(@Nullable User nullableUser) {this.nullableUser = nullableUser;notifyPropertyChanged(BR.nullableUser);invalidateAll();}// 获取nullableUser变量的方法@Nullablepublic User getNullableUser() {return nullableUser;}// 设置nonNullUser变量的方法public void setNonNullUser(@NonNull User nonNullUser) {this.nonNullUser = nonNullUser;notifyPropertyChanged(BR.nonNullUser);invalidateAll();}// 获取nonNullUser变量的方法@NonNullpublic User getNonNullUser() {return nonNullUser;}
}

// 生成的Binding类中对生命周期的处理
public class ActivityMainBinding extends ViewDataBinding {@Nullableprivate User user;  // User对象变量@Nullableprivate LifecycleOwner lifecycleOwner;  // 生命周期所有者// 设置生命周期所有者的方法@Overridepublic void setLifecycleOwner(@Nullable LifecycleOwner lifecycleOwner) {this.lifecycleOwner = lifecycleOwner;// 如果已有LiveData观察者，先移除if (userLiveData != null && this.lifecycleOwner != null) {userLiveData.removeObservers(this.lifecycleOwner);}// 如果有新的生命周期所有者和LiveData，添加观察者if (this.lifecycleOwner != null && userLiveData != null) {userLiveData.observe(this.lifecycleOwner, new Observer<User>() {@Overridepublic void onChanged(@Nullable User user) {// 当LiveData中的User对象发生变化时，触发绑定更新setUser(user);}});}}// 在视图销毁时调用的方法@Overrideprotected void onFieldChange(int localFieldId, Object object, int fieldId) {super.onFieldChange(localFieldId, object, fieldId);// 处理各种字段变化事件switch (localFieldId) {case 0:// User对象的属性发生变化invalidateAll();break;case 1:// LiveData中的数据发生变化User newUser = (User) object;setUser(newUser);break;}}// 释放资源的方法@Overridepublic void executePendingBindings() {super.executePendingBindings();// 执行待处理的绑定操作if (lifecycleOwner != null && lifecycleOwner.getLifecycle().getCurrentState().isAtLeast(Lifecycle.State.DESTROYED)) {// 视图已销毁，释放资源if (userLiveData != null) {userLiveData.removeObservers(lifecycleOwner);}lifecycleOwner = null;}}
}

// 生成的Binding类中的资源释放逻辑
public class ActivityMainBinding extends ViewDataBinding {@Nullableprivate User user;  // User对象变量@Nullableprivate OnPropertyChangedCallback userCallback;  // 用户属性变化回调@Nullableprivate LifecycleOwner lifecycleOwner;  // 生命周期所有者// 释放资源的方法@Overrideprotected void finalize() throws Throwable {try {// 释放资源unbind();} finally {super.finalize();}}// 解绑方法@Overridepublic void unbind() {super.unbind();// 移除监听器if (user != null && userCallback != null) {user.removeOnPropertyChangedCallback(userCallback);}// 移除LiveData观察者if (lifecycleOwner != null && userLiveData != null) {userLiveData.removeObservers(lifecycleOwner);}// 清空引用user = null;userCallback = null;lifecycleOwner = null;userLiveData = null;}
}

// 简化的DataBinding注解处理器
@SupportedAnnotationTypes("androidx.databinding.Bindable")
@SupportedSourceVersion(SourceVersion.RELEASE_8)
public class DataBindingProcessor extends AbstractProcessor {private Filer filer;  // 文件生成器private Messager messager;  // 消息处理器@Overridepublic synchronized void init(ProcessingEnvironment processingEnv) {super.init(processingEnv);filer = processingEnv.getFiler();messager = processingEnv.getMessager();}@Overridepublic boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) {// 处理@Bindable注解Set<? extends Element> bindableElements = roundEnv.getElementsAnnotatedWith(Bindable.class);for (Element element : bindableElements) {if (element.getKind() == ElementKind.METHOD) {// 处理getter方法MethodElement methodElement = (MethodElement) element;processBindableGetter(methodElement);}}// 处理布局文件processLayoutFiles();return true;}// 处理Bindable注解的getter方法private void processBindableGetter(MethodElement methodElement) {// 获取方法所在的类TypeElement classElement = (TypeElement) methodElement.getEnclosingElement();// 获取属性名称String methodName = methodElement.getSimpleName().toString();String propertyName = getPropertyName(methodName);// 生成BR类中的常量generateBRConstant(classElement, propertyName);}// 处理布局文件private void processLayoutFiles() {// 查找所有布局文件Set<File> layoutFiles = findLayoutFiles();for (File layoutFile : layoutFiles) {try {// 解析布局文件LayoutInfo layoutInfo = parseLayoutFile(layoutFile);// 生成绑定类generateBindingClass(layoutInfo);} catch (Exception e) {messager.printMessage(Diagnostic.Kind.ERROR, "Error processing layout file: " + layoutFile.getName());}}}// 生成绑定类private void generateBindingClass(LayoutInfo layoutInfo) throws IOException {// 创建Java文件JavaFileObject jfo = filer.createSourceFile(layoutInfo.getBindingClassName());Writer writer = jfo.openWriter();try {// 生成包声明writer.write("package " + layoutInfo.getPackageName() + ";\n\n");// 生成导入语句writer.write("import androidx.databinding.BaseObservable;\n");writer.write("import androidx.databinding.Bindable;\n");writer.write("import androidx.databinding.ViewDataBinding;\n");writer.write("import android.view.View;\n");writer.write("import " + layoutInfo.getModelClass() + ";\n\n");// 生成类声明writer.write("public class " + layoutInfo.getBindingClassName() + " extends ViewDataBinding {\n\n");// 生成成员变量writer.write("    private " + layoutInfo.getModelClass() + " mModel;\n\n");// 生成构造方法writer.write("    public " + layoutInfo.getBindingClassName() + "(View root) {\n");writer.write("        super(root);\n");writer.write("    }\n\n");// 生成设置模型的方法writer.write("    public void setModel(" + layoutInfo.getModelClass() + " model) {\n");writer.write("        mModel = model;\n");writer.write("        invalidateAll();\n");writer.write("    }\n\n");// 生成获取模型的方法writer.write("    public " + layoutInfo.getModelClass() + " getModel() {\n");writer.write("        return mModel;\n");writer.write("    }\n\n");// 生成绑定方法writer.write("    @Override\n");writer.write("    protected void executeBindings() {\n");writer.write("        if (mModel != null) {\n");// 生成属性绑定代码for (BindingInfo binding : layoutInfo.getBindings()) {writer.write("            " + binding.getViewId() + ".setText(mModel." + binding.getProperty() + ");\n");}writer.write("        }\n");writer.write("    }\n\n");writer.write("}\n");} finally {writer.close();}}// 其他辅助方法...
}

// 生成的ActivityMainBinding类示例
public class ActivityMainBinding extends ViewDataBinding {@NonNullprivate final LinearLayout rootView;@NonNullpublic final TextView textViewName;@NonNullpublic final TextView textViewAge;@Nullableprivate User mUser;// 构造方法public ActivityMainBinding(@NonNull View root) {super(root);this.rootView = (LinearLayout) root;this.textViewName = findViewById(root, R.id.textViewName);this.textViewAge = findViewById(root, R.id.textViewAge);}// 获取根视图@Override@NonNullpublic LinearLayout getRoot() {return rootView;}// 设置User变量public void setUser(@Nullable User user) {mUser = user;invalidateAll();}// 获取User变量@Nullablepublic User getUser() {return mUser;}// 执行绑定操作@Overrideprotected void executeBindings() {User userValue = mUser;String nameValue = null;int ageValue = 0;if (userValue != null) {nameValue = userValue.getName();ageValue = userValue.getAge();}textViewName.setText(nameValue);textViewAge.setText(String.valueOf(ageValue));}
}

// 生成的BR类示例
public class BR {public static final int _all = 0;public static final int name = 1;public static final int age = 2;public static final int user = 3;public static final int viewModel = 4;// 其他属性ID...
}

// 在Activity中初始化DataBinding
public class MainActivity extends AppCompatActivity {private ActivityMainBinding binding;  // 绑定类实例@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);// 初始化DataBindingbinding = ActivityMainBinding.inflate(getLayoutInflater());setContentView(binding.getRoot());// 创建User对象User user = new User("John Doe", 30);// 设置数据变量binding.setUser(user);// 设置生命周期所有者（可选，用于LiveData）binding.setLifecycleOwner(this);}
}

// 可观察的User类
public class User extends BaseObservable {private String name;private int age;public User(String name, int age) {this.name = name;this.age = age;}// 获取姓名@Bindablepublic String getName() {return name;}// 设置姓名，并通知变更public void setName(String name) {this.name = name;notifyPropertyChanged(BR.name);}// 获取年龄@Bindablepublic int getAge() {return age;}// 设置年龄，并通知变更public void setAge(int age) {this.age = age;notifyPropertyChanged(BR.age);}
}

// 绑定表达式求值的简化实现
public class BindingExpressionEvaluator {// 求值方法public static Object evaluateExpression(String expression, Map<String, Object> variables) {// 解析表达式ExpressionParser parser = new ExpressionParser(expression);ExpressionNode rootNode = parser.parse();// 求值return evaluateNode(rootNode, variables);}// 对表达式节点求值private static Object evaluateNode(ExpressionNode node, Map<String, Object> variables) {if (node instanceof LiteralNode) {// 字面量节点return ((LiteralNode) node).getValue();} else if (node instanceof VariableNode) {// 变量节点String variableName = ((VariableNode) node).getName();return variables.get(variableName);} else if (node instanceof PropertyAccessNode) {// 属性访问节点PropertyAccessNode propertyNode = (PropertyAccessNode) node;Object target = evaluateNode(propertyNode.getTarget(), variables);if (target == null) {return null;}String propertyName = propertyNode.getPropertyName();// 通过反射获取属性值try {Method method = getGetterMethod(target.getClass(), propertyName);if (method != null) {return method.invoke(target);}} catch (Exception e) {e.printStackTrace();}return null;} else if (node instanceof MethodCallNode) {// 方法调用节点MethodCallNode methodNode = (MethodCallNode) node;Object target = evaluateNode(methodNode.getTarget(), variables);if (target == null) {return null;}String methodName = methodNode.getMethodName();List<ExpressionNode> arguments = methodNode.getArguments();// 准备参数Object[] argValues = new Object[arguments.size()];for (int i = 0; i < arguments.size(); i++) {argValues[i] = evaluateNode(arguments.get(i), variables);}// 通过反射调用方法try {Method method = findMethod(target.getClass(), methodName, argValues);if (method != null) {return method.invoke(target, argValues);}} catch (Exception e) {e.printStackTrace();}return null;} else if (node instanceof BinaryOperationNode) {// 二元运算节点BinaryOperationNode binaryNode = (BinaryOperationNode) node;Object left = evaluateNode(binaryNode.getLeft(), variables);Object right = evaluateNode(binaryNode.getRight(), variables);// 执行运算return performOperation(binaryNode.getOperation(), left, right);}return null;}// 其他辅助方法...
}

<!-- 布局文件中多变量绑定示例 -->
<data><variablename="user"type="com.example.User" /><variablename="config"type="com.example.Config" />
</data><LinearLayoutandroid:layout_width="match_parent"android:layout_height="match_parent"android:orientation="vertical"><!-- 结合两个变量的表达式 --><TextViewandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:text="@{user.name + ` (ID: ` + config.userId + `)`}" /><!-- 基于多个变量的条件表达式 --><TextViewandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:visibility="@{user.isPremium && config.showPremium ? View.VISIBLE : View.GONE}"android:text="Premium User" />
</LinearLayout>

<!-- 布局文件中动态变量类型示例 -->
<data><variablename="data"type="java.lang.Object" />
</data><LinearLayoutandroid:layout_width="match_parent"android:layout_height="match_parent"android:orientation="vertical"><!-- 根据数据类型显示不同内容 --><TextViewandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:text="@{data instanceof com.example.User ? ((User)data).name : data.toString()}" /><!-- 根据数据类型显示不同视图 --><Viewandroid:id="@+id/userView"android:layout_width="match_parent"android:layout_height="wrap_content"android:visibility="@{data instanceof com.example.User ? View.VISIBLE : View.GONE}" /><Viewandroid:id="@+id/otherView"android:layout_width="match_parent"android:layout_height="wrap_content"android:visibility="@{data instanceof com.example.User ? View.GONE : View.VISIBLE}" />
</LinearLayout>

<!-- 布局文件中集合数据绑定示例 -->
<data><variablename="users"type="java.util.List<com.example.User">>" />
</data><LinearLayoutandroid:layout_width="match_parent"android:layout_height="match_parent"android:orientation="vertical"><!-- 使用RecyclerView展示列表数据 --><androidx.recyclerview.widget.RecyclerViewandroid:layout_width="match_parent"android:layout_height="match_parent"app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"app:adapter="@{new com.example.UserAdapter(users)}" />
</LinearLayout>

// UserAdapter类示例
public class UserAdapter extends RecyclerView.Adapter<UserAdapter.UserViewHolder> {private List<User> users;  // 用户列表public UserAdapter(List<User> users) {this.users = users;}@NonNull@Overridepublic UserViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {// 加载布局LayoutInflater inflater = LayoutInflater.from(parent.getContext());ItemUserBinding binding = ItemUserBinding.inflate(inflater, parent, false);return new UserViewHolder(binding);}@Overridepublic void onBindViewHolder(@NonNull UserViewHolder holder, int position) {// 获取当前位置的用户User user = users.get(position);// 设置数据holder.binding.setUser(user);holder.binding.executePendingBindings();}@Overridepublic int getItemCount() {return users == null ? 0 : users.size();}// ViewHolder类public static class UserViewHolder extends RecyclerView.ViewHolder {private ItemUserBinding binding;  // 项布局的绑定类public UserViewHolder(@NonNull ItemUserBinding binding) {super(binding.getRoot());this.binding = binding;}}
}

// 优化后的绑定类示例
public class OptimizedActivityBinding extends ViewDataBinding {@NonNullprivate final LinearLayout rootView;@NonNullpublic final TextView textViewName;@NonNullpublic final TextView textViewAge;@Nullableprivate User mUser;// 使用弱引用避免内存泄漏private WeakReference<Context> contextRef;// 构造方法public OptimizedActivityBinding(@NonNull View root, @NonNull Context context) {super(root);this.rootView = (LinearLayout) root;this.textViewName = findViewById(root, R.id.textViewName);this.textViewAge = findViewById(root, R.id.textViewAge);this.contextRef = new WeakReference<>(context);}// 设置User变量，使用DiffUtil检测变化public void setUser(@Nullable User user) {if (DataUtil.areItemsTheSame(mUser, user)) {if (!DataUtil.areContentsTheSame(mUser, user)) {mUser = user;invalidateAll();}} else {mUser = user;invalidateAll();}}// 执行绑定操作，优化更新逻辑@Overrideprotected void executeBindings() {User userValue = mUser;String nameValue = null;int ageValue = 0;if (userValue != null) {nameValue = userValue.getName();ageValue = userValue.getAge();}// 使用setTextIfChanged避免不必要的更新setTextIfChanged(textViewName, nameValue);setTextIfChanged(textViewAge, String.valueOf(ageValue));}// 避免重复设置相同文本的辅助方法private void setTextIfChanged(TextView textView, String text) {if (!textView.getText().toString().equals(text)) {textView.setText(text);}}
}

<data><import type="androidx.lifecycle.LiveData" alias="Live" /><import type="androidx.lifecycle.MutableLiveData" alias="MutableLive" /><variablename="userLiveData"type="Live<com.example.User">>" />
</data>

<data><variablename="user"type="com.example.User" />
</data><EditTextandroid:layout_width="match_parent"android:layout_height="wrap_content"android:text="@={user.name}" /> <!-- 双向绑定 -->

// 自定义绑定适配器示例
public class BindingAdapters {@BindingAdapter("imageUrl")public static void loadImage(ImageView view, String url) {Glide.with(view.getContext()).load(url).into(view);}@BindingAdapter("android:visibility")public static void setVisibility(View view, Boolean visible) {view.setVisibility(visible ? View.VISIBLE : View.GONE);}
}

<data><variablename="isPremium"type="boolean" />
</data><LinearLayoutandroid:layout_width="match_parent"android:layout_height="match_parent"android:orientation="vertical"><Viewandroid:id="@+id/premiumFeature"android:layout_width="match_parent"android:layout_height="wrap_content"android:visibility="@{isPremium ? View.VISIBLE : View.GONE}" />
</LinearLayout>

// ViewModel类示例
public class MainViewModel extends ViewModel {private MutableLiveData<User> userLiveData = new MutableLiveData<>();public MainViewModel() {// 初始化用户数据User user = new User("John Doe", 30);userLiveData.setValue(user);}// 获取用户数据public LiveData<User> getUser() {return userLiveData;}// 更新用户数据public void updateUserName(String name) {User user = userLiveData.getValue();if (user != null) {user.setName(name);userLiveData.setValue(user);}}
}

<!-- 布局文件中与ViewModel集成 -->
<data><variablename="viewModel"type="com.example.MainViewModel" />
</data><LinearLayoutandroid:layout_width="match_parent"android:layout_height="match_parent"android:orientation="vertical"><TextViewandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:text="@{viewModel.user.name}" /><EditTextandroid:layout_width="match_parent"android:layout_height="wrap_content"android:text="@={viewModel.user.name}" />
</LinearLayout>

// Activity中集成ViewModel和DataBinding
public class MainActivity extends AppCompatActivity {private ActivityMainBinding binding;private MainViewModel viewModel;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);// 初始化DataBindingbinding = ActivityMainBinding.inflate(getLayoutInflater());setContentView(binding.getRoot());// 初始化ViewModelviewModel = new ViewModelProvider(this).get(MainViewModel.class);// 设置ViewModel到DataBindingbinding.setViewModel(viewModel);// 设置生命周期所有者binding.setLifecycleOwner(this);}
}

// 使用LiveData的ViewModel
public class MyViewModel extends ViewModel {private MutableLiveData<String> messageLiveData = new MutableLiveData<>();public MyViewModel() {messageLiveData.setValue("Hello DataBinding!");}// 获取消息LiveDatapublic LiveData<String> getMessage() {return messageLiveData;}// 更新消息public void updateMessage(String message) {messageLiveData.setValue(message);}
}

<!-- 布局文件中与LiveData集成 -->
<data><variablename="viewModel"type="com.example.MyViewModel" />
</data><LinearLayoutandroid:layout_width="match_parent"android:layout_height="match_parent"android:orientation="vertical"><TextViewandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:text="@{viewModel.message}" /><Buttonandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:text="Update Message"android:onClick="@{() -> viewModel.updateMessage(`New Message`)}" />
</LinearLayout>

// Room实体类
@Entity(tableName = "users")
public class User {@PrimaryKey(autoGenerate = true)private int id;private String name;private int age;// 构造方法和getter/setter方法public User(String name, int age) {this.name = name;this.age = age;}public int getId() {return id;}public void setId(int id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}
}

// Room DAO接口
@Dao
public interface UserDao {@Query("SELECT * FROM users")LiveData<List<User>> getAllUsers();@Insertvoid insert(User user);@Updatevoid update(User user);@Deletevoid delete(User user);
}

// Room数据库
@Database(entities = {User.class}, version = 1)
public abstract class AppDatabase extends RoomDatabase {public abstract UserDao userDao();
}

// Repository类
public class UserRepository {private UserDao userDao;private LiveData<List<User>> allUsers;public UserRepository(Application application) {AppDatabase database = Room.databaseBuilder(application,AppDatabase.class, "user-database").build();userDao = database.userDao();allUsers = userDao.getAllUsers();}public LiveData<List<User>> getAllUsers() {return allUsers;}public void insert(User user) {new InsertUserAsyncTask(userDao).execute(user);}private static class InsertUserAsyncTask extends AsyncTask<User, Void, Void> {private UserDao userDao;private InsertUserAsyncTask(UserDao userDao) {this.userDao = userDao;}@Overrideprotected Void doInBackground(User... users) {userDao.insert(users[0]);return null;}}
}

// ViewModel类
public class UserViewModel extends AndroidViewModel {private UserRepository repository;private LiveData<List<User>> allUsers;public UserViewModel(@NonNull Application application) {super(application);repository = new UserRepository(application);allUsers = repository.getAllUsers();}public LiveData<List<User>> getAllUsers() {return allUsers;}public void insert(User user) {repository.insert(user);}
}

<!-- 布局文件中与Room集成 -->
<data><variablename="viewModel"type="com.example.UserViewModel" />
</data><LinearLayoutandroid:layout_width="match_parent"android:layout_height="match_parent"android:orientation="vertical"><androidx.recyclerview.widget.RecyclerViewandroid:layout_width="match_parent"android:layout_height="match_parent"app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"app:adapter="@{new com.example.UserAdapter(viewModel.allUsers)}" />
</LinearLayout>