Java 如何在 Android 上实现 OnClickListener

How to implement OnClickListener on Android

提问by Bamqf

I learn from

我从

http://developer.android.com/reference/android/widget/Button.html

that "instead of applying an OnClickListener to the button in your activity, you can assign a method to your button in the XML layout, using the android:onClick attribute."

“您可以使用 android:onClick 属性为 XML 布局中的按钮分配一个方法，而不是将 OnClickListener 应用于您的活动中的按钮。”

However, I can only get it done with the XML approach, my Listener approach, specified by the following, leads to app crash.

但是，我只能使用 XML 方法来完成它，我的 Listener 方法（由以下指定）导致应用程序崩溃。

In my fragment_main.xml:

在我的 fragment_main.xml 中：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.example.myapp.MainActivity$PlaceholderFragment" >

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/hello_world" />
    <Button
        android:id="@+id/try_button" 
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text = "TryButton"
        android:onClick="onClick"
    />
</RelativeLayout>

In my activity_main.xml:

在我的 activity_main.xml 中：

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.myapp.MainActivity"
    tools:ignore="MergeRootFrame">
</FrameLayout>

And in my MainActivity.java:

在我的 MainActivity.java 中：

public class MainActivity extends Activity implements OnClickListener{

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    if (savedInstanceState == null) {
        getFragmentManager().beginTransaction()
                .add(R.id.container, new PlaceholderFragment()).commit();
    }

    Button button = (Button)findViewById(R.id.try_button);      
    button.setOnClickListener(this);
}
public void onClick(View v) {
    Toast.makeText(getApplicationContext(), "I'm clicked!", Toast.LENGTH_SHORT).show();;
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {

    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();
    if (id == R.id.action_settings) {
        return true;
    }
    return super.onOptionsItemSelected(item);
}

/**
 * A placeholder fragment containing a simple view.
 */
public static class PlaceholderFragment extends Fragment {

    public PlaceholderFragment() {
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_main, container,
                false);
        return rootView;
    }
}

}

}

The LogCat says:

LogCat 说：

05-20 19:56:17.604: E/MoreInfoHPW_ViewGroup(566): Parent view is not a TextView
05-20 19:56:17.649: D/AndroidRuntime(566): Shutting down VM
05-20 19:56:17.649: W/dalvikvm(566): threadid=1: thread exiting with uncaught exception (group=0x4194ec08)
05-20 19:56:17.654: E/AndroidRuntime(566): FATAL EXCEPTION: main
05-20 19:56:17.654: E/AndroidRuntime(566): Process: com.example.myapp, PID: 566
05-20 19:56:17.654: E/AndroidRuntime(566): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.myapp/com.example.myapp.MainActivity}: java.lang.NullPointerException
05-20 19:56:17.654: E/AndroidRuntime(566):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2328)
05-20 19:56:17.654: E/AndroidRuntime(566):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2386)
05-20 19:56:17.654: E/AndroidRuntime(566):  at android.app.ActivityThread.access0(ActivityThread.java:169)
05-20 19:56:17.654: E/AndroidRuntime(566):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1277)
05-20 19:56:17.654: E/AndroidRuntime(566):  at android.os.Handler.dispatchMessage(Handler.java:102)
05-20 19:56:17.654: E/AndroidRuntime(566):  at android.os.Looper.loop(Looper.java:136)
05-20 19:56:17.654: E/AndroidRuntime(566):  at android.app.ActivityThread.main(ActivityThread.java:5476)
05-20 19:56:17.654: E/AndroidRuntime(566):  at java.lang.reflect.Method.invokeNative(Native Method)
05-20 19:56:17.654: E/AndroidRuntime(566):  at java.lang.reflect.Method.invoke(Method.java:515)
05-20 19:56:17.654: E/AndroidRuntime(566):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1268)
05-20 19:56:17.654: E/AndroidRuntime(566):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1084)
05-20 19:56:17.654: E/AndroidRuntime(566):  at dalvik.system.NativeStart.main(Native Method)
05-20 19:56:17.654: E/AndroidRuntime(566): Caused by: java.lang.NullPointerException
05-20 19:56:17.654: E/AndroidRuntime(566):  at com.example.myapp.MainActivity.onCreate(MainActivity.java:29)
05-20 19:56:17.654: E/AndroidRuntime(566):  at android.app.Activity.performCreate(Activity.java:5473)
05-20 19:56:17.654: E/AndroidRuntime(566):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1093)
05-20 19:56:17.654: E/AndroidRuntime(566):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2292)
05-20 19:56:17.654: E/AndroidRuntime(566):  ... 11 more

I'm using latest Eclipse ADT v22.6.2 on Windows 7, running on Samsung Galaxy Note 10.1 2014.

我在 Windows 7 上使用最新的 Eclipse ADT v22.6.2，在 Samsung Galaxy Note 10.1 2014 上运行。

What's wrong with my code?

我的代码有什么问题？

采纳答案by araut

Try this:

尝试这个：

public class MainActivity extends Activity  {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    if (savedInstanceState == null) {
        getFragmentManager().beginTransaction()
            .add(R.id.container, new PlaceholderFragment()).commit();
    }

    //Button button = (Button)findViewById(R.id.try_button);      
    //button.setOnClickListener(this);
}

/**
public void onClick(View v) {

}
*/

@Override
public boolean onCreateOptionsMenu(Menu menu) {

    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();
    if (id == R.id.action_settings) {
        return true;
    }
    return super.onOptionsItemSelected(item);
}

/**
 * A placeholder fragment containing a simple view.
 */
public static class PlaceholderFragment extends Fragment implements OnClickListener {

public PlaceholderFragment() {
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
    View rootView = inflater.inflate(R.layout.fragment_main, container,
            false);

  Button button = (Button) rootView.findViewById(R.id.try_button);      
  button.setOnClickListener(this);

    return rootView;
}

@Override
public void onClick(View v) {
    // TODO Auto-generated method stub
    Toast.makeText(getActivity(), "I'm clicked!", Toast.LENGTH_SHORT).show();
}

}
}

回答by Chefes

You don't need implement OnClickListener, because your button execute the method automatically.

您不需要实现 OnClickListener，因为您的按钮会自动执行该方法。

Edit:

编辑：

public class MainActivity extends Activity {

private OnClickListener onClickListener;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    if (savedInstanceState == null) {
        getFragmentManager().beginTransaction()
                .add(R.id.container, new PlaceholderFragment()).commit();
    }
    initListener();//Initializing Listener.
    Button button = (Button)findViewById(R.id.try_button);
    //This command causes problem
    button.setOnClickListener(onClickListener);
}

private void initListener(){
         onclickListener = new OnClickListener() {
               @Override
                public void onClick(View view) {
                      Toast.makeText(getApplicationContext(),
                      "Button Clicked",Toast.LENGTH_SHORT).show();
                }
         };
}

Quit the Onclick in your XML.

退出 XML 中的 Onclick。

<Button
        android:id="@+id/try_button" 
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text = "TryButton"
    />

回答by Jenron19

XML : android:onClick="onclickid"

XML : android:onClick="onclickid"

Activity :

活动 ：

public void onclickid(View view)
  {
 //Do something When the button is click
  }

This Should Help, But i suggest to use onclicklistener

这应该有帮助，但我建议使用 onclicklistener

回答by user1103538

I've explained the different ways you can implement an OnClickListener on my blog: http://www.androiddevresources.com/guides/tutorial-how-to-implement-an-onclicklistener/

我已经在我的博客上解释了实现 OnClickListener 的不同方式：http://www.androiddevresources.com/guides/tutorial-how-to-implement-an-onclicklistener/

Basically there are three ways. - Implement the listener in the activity class (and set the xml attribute) - Create a variable in your activity class (or other class, for example a fragment). - Create a new listener in line with new OnClickListener().

基本上有三种方式。- 在活动类中实现侦听器（并设置 xml 属性） - 在您的活动类（或其他类，例如片段）中创建一个变量。- 根据 new OnClickListener() 创建一个新的监听器。

I've added example code in the article and an example project on GitHub which you can download.

我在文章中添加了示例代码，并在 GitHub 上添加了一个示例项目，您可以下载。

回答by Sadaf Ayaz

public class start extends Activity implements View.OnClickListener { Button bSMS;

公共类开始扩展 Activity 实现 View.OnClickListener { Button bSMS;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_start);
    bSMS = (Button) findViewById(R.id.button);


    bSMS.setOnClickListener(this);

}

@Override
public void onClick(View arg0) {
    // TODO Auto-generated method stub

    switch (arg0.getId()) {

        case R.id.button:        //"Block SMSs" button pressed
            startActivity(new Intent(this,secret_main.class));
            break;

    }
}

}

}