android {
    dataBinding {
        enabled true
    }
}

<layout xmlns:android="http://schemas.android.com/apk/res/android">
    <data> …  </data>  //新增的data节点 
    
    <LinearLayout> ... </LinearLayout>  //原先的根节点
</layout>

public class User {
    private String firstName;//就是一个简单的Java Bean
    private String lastName;
    ...
}

<data>
    <variable name="user" type="com.bqt.basic.User" />
</data>

<data>
    <import type="com.bqt.basic.User" />
    <variable name="user" type="User" />
</data>

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    //用 DatabindingUtil.setContentView() 来替换掉 setContentView()
    MainActivityBinding binding = DataBindingUtil.setContentView(this, R.layout.main_activity);
    ...
}

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="@{user.lastName}" />

/**
 * Notifies listeners that a specific property has changed. The getter for the property
 * that changes should be marked with @Bindable to generate a field in BR to be used as fieldId.
 * @param fieldId The generated BR id for the Bindable field.
 */
public void notifyPropertyChanged(int fieldId) {
    synchronized (this) {
        if (mCallbacks == null) return;//private transient PropertyChangeRegistry mCallbacks;
    }
    mCallbacks.notifyCallbacks(this, fieldId, null);//通过【PropertyChangeRegistry】来实现通知监听器
}

package com.bqt.databinding;
public class BR {
    ...
    public static final int name = 17;
    ...
}

android:padding="@{large? @dimen/largePadding : @dimen/smallPadding}"
//dimens.xml中的定义
<dimen name="largePadding">20dp</dimen>

android:padding="@{large ? (int)@dimen/largePadding : (int)@dimen/smallPadding}"  //错误写法

android:text="@{@string/nameFormat(firstName, lastName)}"

<string name="nameFormat">Full Name: %1$s %2$s</string> //格式化字符串

<ViewStub
    android:id="@+id/m_view_stub"
    android:layout="@layout/m_view_stub"
    android:layout_width="match_parent"
    android:layout_height="wrap_content" />

mBinding.mViewStub.setOnInflateListener(new ViewStub.OnInflateListener() {//监听ViewStub的OnInflateListener监听器
    @Override
    public void onInflate(ViewStub stub, View inflated) {//当载入另一个layout时为新的布局创建一个Binding
        MViewStubBinding binding = DataBindingUtil.bind(inflated);//同样，此Binding的名字取决于ViewStub布局的名字。
        User user = new User("fee", "lang");
        binding.setUser(user);//此Binding只能处理ViewStub布局中带id的View或变量，而不能处理根布局中的东西
    }
});

//填充ViewStub
if (!mBinding.mViewStub.isInflated())  mBinding.mViewStub.getViewStub().inflate();

static class UserAdapter extends RecyclerView.Adapter<UserAdapter.UserHolder> {
	
	private List<User> mUsers;
	
	public UserAdapter(List<User> mUsers) {
		this.mUsers = mUsers;
	}
	
	static class UserHolder extends RecyclerView.ViewHolder {//最主要的区别就是在这里！
		private UserItemBinding mBinding;
		
		public UserHolder(View itemView) {
			super(itemView);
			mBinding = DataBindingUtil.bind(itemView);//【在构造 Holder 时把 itemView 与自动生成的 XXXBinding 进行绑定】
		}
		
		public void bind(User user) {
			mBinding.setUser(user);//绑定数据
		}
	}
	
	@Override
	public int getItemCount() {
		return mUsers.size();
	}
	
	@Override
	public UserHolder onCreateViewHolder(ViewGroup viewGroup, int i) {
		View itemView = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.user_item, viewGroup, false);
		return new UserHolder(itemView);
	}
	
	@Override
	public void onBindViewHolder(UserHolder holder, int position) {
		holder.bind(mUsers.get(position));//只需要为每一个item绑定数据，而不需要手动操作item中的UI
	}
	
}

<android.support.v4.widget.DrawerLayout
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    app:scrimColor="@{@color/scrim}"
    app:drawerListener="@{fragment.drawerListener}"/>

@Target(ElementType.ANNOTATION_TYPE)
public @interface BindingMethod {
    Class type();//The View Class that the attribute is associated with.
    String attribute();//The attribute to rename. Use android: namespace for all android attributes or no namespace for application attributes.
    String method();//The method to call to set the attribute value.
}

@Target({ElementType.TYPE})
public @interface BindingMethods {
    BindingMethod[] value();
}

@BindingMethods({
        @BindingMethod(type = TextView.class, attribute = "android:autoLink", method = "setAutoLinkMask"),
        @BindingMethod(type = TextView.class, attribute = "android:drawablePadding", method = "setCompoundDrawablePadding"),
        ...
})
public class TextViewBindingAdapter { ... }

@Target(ElementType.METHOD)
public @interface BindingAdapter {
    String[] value();//The attributes associated with this binding adapter.
    boolean requireAll() default true;
}

@BindingAdapter("android:bufferType")
 public static void setBufferType(TextView view, TextView.BufferType bufferType) {
     view.setText(view.getText(), bufferType);
 }

@BindingAdapter("android:onLayoutChange")
public static void setOnLayoutChangeListener(View view, View.OnLayoutChangeListener oldValue, View.OnLayoutChangeListener newValue) {
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
        if (oldValue != null) view.removeOnLayoutChangeListener(oldValue);//先移除旧的
        if (newValue != null) view.addOnLayoutChangeListener(newValue);//再添加新的
    }
}

@BindingAdapter({"android:onClick", "android:clickable"})
public static void setOnClick(View view, View.OnClickListener clickListener, boolean clickable) {
    view.setOnClickListener(clickListener);
    view.setClickable(clickable);
}

<variable name="pt" type="int"/>
android:paddingTop="@{pt}"

@BindingAdapter({"android:paddingTop"})
public static void setPaddingTopAndBottom(View view, int paddingTB) {//当设置paddingTop时，同时设置paddingTop和paddingBottom
	view.setPadding(view.getPaddingLeft(), paddingTB, view.getPaddingRight(), paddingTB);
}

mBinding.setPt(10 * new Random().nextInt(10));

<com.liangfeizc.avatarview.AvatarView
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    app:error="@{@drawable/error}"
    app:imageUrl="@{imageUrl}"
    app:onClickListener="@{activity.mClickListener}"/>

@BindingAdapter({"bind:imageUrl", "error"})//自定义 namespaces 将被忽略
public static void loadBqtImage(ImageView view, String url, Drawable error) {//方法名随意，但参数必须和注解中指定的属性一一对应
	Picasso.with(view.getContext()).load(url).error(error).into(view);
}

<TextView
  android:text=‘@{userMap["lastName"]}‘
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"/>

@Target({ElementType.METHOD})
public @interface BindingConversion {
}

<View
  android:background="@{isError ? @color/red : @color/white}"
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"/>

@BindingConversion
public static ColorDrawable convertColorToDrawable(int color) {
  return new ColorDrawable(color);
}

<View
  android:background="@{isError ? @drawable/error : @color/white}"
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"/>

/**
 * !!! Binding conversion should be forbidden, otherwise it will conflict with{@code android:visiblity} attribute.
 */
@BindingConversion
public static int convertColorToString(int color) {
	switch (color) {
		case Color.RED:
			return R.string.red;
		case Color.WHITE:
			return R.string.white;
	}
	return R.string.app_name;
}