无法在android数据绑定中生成click事件

Question

View.Java

package com.espresso.mvvmtestproject;

import android.content.Context;
import android.databinding.DataBindingUtil;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

import com.espresso.mvvmtestproject.databinding.ActivityMainBinding;


public class View extends AppCompatActivity implements ViewContract.requiredMethods{


    ViewModel mModel;
    ActivityMainBinding binding;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //Setting the layout
        binding = DataBindingUtil.setContentView(this, R.layout.activity_main);
        mModel=new ViewModel(getContext());
        binding.setUser(mModel);
        binding.setHandlers(new MyHandlers());

    }

    @Override
    public void onDestroy() {
        super.onDestroy();

    }

    @Override
    public Context getContext() {
        return View.this;
    }


}

---

ViewContract.java

public interface ViewContract {
    interface requiredMethods{
        Context getContext();
    }
}

---

activity_main.xml中

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android">

    <data>
        <variable
            name="user"
            type="com.espresso.mvvmtestproject.ViewModel"/>
        <variable
            name="handlers"
            type="com.espresso.mvvmtestproject.MyHandlers"/>
    </data>




    <LinearLayout
        android:orientation="vertical"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_gravity="center"
        android:gravity="center">
        <TextView android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:textSize="20sp"
            android:layout_gravity="center"
            android:gravity="center"
            android:textColor="@android:color/black"
            android:text="First Text"/>
        <TextView android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:textSize="20sp"
            android:layout_gravity="center"
            android:gravity="center"
            android:textColor="@android:color/black"
            android:text="Second Text"/>

        <Button
            android:text="Show Toast"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:onClick="@{handlers::onShowToast}"/>
    </LinearLayout>

</layout>

---

MyHandlers.java

public class MyHandlers {

    public void onShowToast(View view) {
        Toast.makeText(view,"Clicked",Toast.LENGTH_SHORT).show();
    }

}

ViewModel.java

public class ViewModel {


    private Context mActivity;

    public ViewModel(Context context) {
        this.mActivity=context;
    }

    public void onShowToast(View view) {
        Toast.makeText(mActivity,"Clicked",Toast.LENGTH_SHORT).show();
    }

}

---

错误日志

Information:Gradle tasks [:app:clean, :app:generateDebugSources, :app:mockableAndroidJar, :app:prepareDebugUnitTestDependencies, :app:generateDebugAndroidTestSources, :app:assembleDebug]
D:\Projects\Trp\MvvmTestProject\app\src\main\java\com\espresso\mvvmtestproject\View.java
Error:(8, 48) error: package com.espresso.mvvmtestproject.databinding does not exist
Error:(15, 5) error: cannot find symbol class ActivityMainBinding
Error:Execution failed for task ':app:compileDebugJavaWithJavac'.
> java.lang.RuntimeException: Found data binding errors.
****/ data binding error ****msg:Listener class android.view.View.OnClickListener with method onClick did not match signature of any method handlers::onShowToast
file:D:\Projects\Trp\MvvmTestProject\app\src\main\res\layout\activity_main.xml
loc:40:31 - 40:51
****\ data binding error ****
Information:BUILD FAILED
Information:Total time: 4.396 secs
Information:3 errors
Information:0 warnings
Information:See complete output in console

Answer 1

在DataBinding库的更高版本中，您可以像这样绑定到click事件：

android:onClick="@{() -> viewModel.save()}"

然后，在您的viewmodel中，您可以像这样添加一个监听器：

public void save(){
 ...
 }

Answer 2

从类中MyHandlers接口。

public class MyHandlers {
    public void onShowToast(View view);
} 

在您的Activity或Fragment实现它，在您的情况下它将如下所示

public class View extends AppCompatActivity implements ViewContract.requiredMethods, MyHandlers{

    ViewModel mModel;
    ActivityMainBinding binding;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //Setting the layout
        binding = DataBindingUtil.setContentView(this, R.layout.activity_main);
        mModel=new ViewModel(getContext());
        binding.setUser(mModel);
        binding.setHandlers(this);

    }        

    @Override
    public void onShowToast(View view) {
        Toast.makeText(view,"Clicked",Toast.LENGTH_SHORT).show();
    }
}

覆盖你的接口方法onShowToast并设置绑定的处理程序，就是这样，你完成了点击事件