我从

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

这，而不是施加OnClickListener到您的活动按钮，你可以指定一个方法，你在XML布局按钮，使用了android：onclick属性

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."

不过，我只能把它与XML的方法做了，我的监听器的方法，通过以下规定，导致应用程序崩溃。

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

在我fragment_main.xml：

In my fragment_main.xml:

<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>

在我activity_main.xml：

In my activity_main.xml:

<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>

和我MainActivity.java：

And in my MainActivity.java:

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;
    }
}

}

在LogCat中说：

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.access$900(ActivityThread.java:169)
05-20 19:56:17.654: E/AndroidRuntime(566):  at android.app.ActivityThread$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

我使用的是最新的Eclipse ADT v22.6.2在Windows 7上，在三星Galaxy Note 10.1上运行2014年。

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

有什么毛病我的code？

What's wrong with my code?

推荐答案

试试这个：

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();
}

}
}