有一个 ViewModel 类，有一个 xml，xml 绑定了 ViewModel .

1. 不带参数：@{() -> viewModel.click()}

<!--xml:-->
...
  <data>
        <variable
            name="vm"
            type="com.xxx.xxx.MainViewModel" />
    </data>
...
<Button
   android:layout_width="match_parent"
   android:layout_height="48dp"
   android:onClick="@{() -> vm.click()}"
...
/>

//ViewModel:
public void click(){
}

2. @{viewModel::click}

<!--xml:-->
...
  <data>
        <variable
            name="vm"
            type="com.xxx.xxx.MainViewModel" />
    </data>
...
<Button
   android:layout_width="match_parent"
   android:layout_height="48dp"
   android:onClick="@{vm::click}"
/>
...

//ViewModel:
public void click(View view){
 }

3. 带参数：@{() -> viewModel.click(obj.id)}

<!--xml:-->
<variable
  name="vm"
  type="com.xx.xxx.ViewModel" />
 
<variable
  name="obj"
  type="com.xx.xxx.User" />
<Button
   android:layout_width="match_parent"
   android:layout_height="48dp"
   android:onClick="@{() -> vm.click(obj.id)}"
/>

//ViewModel:
public void click(long id){
   //do  }

4.ObservableField<OnClickListener>

<!--xml:-->
 <variable
    name="iconView"
    type="com.xxxxx.IconView" />
 
 <RelativeLayout
    android:id="@+id/rl_icon_view"
    android:layout_width="match_parent"
    android:layout_height="55dp"
    android:onClick="@{iconView.clickListener}"
    >  

//IconView:
 public final ObservableField<OnClickListener> clickListener=new ObservableField<>();
 
//xml所在的Activity类：
 binding.iconView.clickListener.set(new View.OnClickListener() {
     @Override
     public void onClick(View v) {
       Toast.makeText(getApplicationContext(),"iconView",Toast.LENGTH_SHORT).show();
     }
 });

5. 带view的参数

<!--xml:-->
<variable
    name="listener"
    type="test.carrie.todomvvmtest.ui.OnTaskItemListener"/>
<Button
   android:layout_width="match_parent"
   android:layout_height="48dp"
 android:onClick="@{(view)->listener.onCheckBoxClick(view,obj)}"
/>

//adapter:
 public void onCheckBoxClick(View v,ToDo entity,) {
 }

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