Android Studio - 應用程序已停止

Question

我正在嘗試Android Studio。我用onClickLister()的按鈕創建了一個簡單的應用程序來顯示Toast消息。我收到消息「應用程序已停止」。

-The相同的代碼工作與Eclipse -I創造更多的項目，試圖 -tried虛擬和實際設備 -Reinstalled Android Studio中

任何想法？

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:paddingLeft="@dimen/activity_horizontal_margin" 
    android:paddingRight="@dimen/activity_horizontal_margin" 
    android:paddingTop="@dimen/activity_vertical_margin" 
    android:paddingBottom="@dimen/activity_vertical_margin" 
    tools:context=".MainActivity$PlaceholderFragment"> 

    <TextView 
     android:text="@string/hello_world" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:id="@+id/textView" /> 

    <Button 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:text="New Button" 
     android:id="@+id/button" 
     android:layout_centerVertical="true" 
     android:layout_centerHorizontal="true" /> 
</RelativeLayout> 

我的活動課在這裏：

public class MainActivity extends ActionBarActivity { 

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

    Button mibtn = (Button)findViewById(R.id.button); 

    mibtn.setOnClickListener(new View.OnClickListener() { 
     @Override 
     public void onClick(View view) { 
      Toast.makeText(getApplicationContext(),"Apretado", Toast.LENGTH_LONG).show(); 
     } 
    }); 

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


@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. 
    switch (item.getItemId()) { 
     case 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; 
    } 
} 

}

的logcat：

01-14 12:43:11.759 5651-5651/? W/dalvikvm﹕ threadid=1: thread exiting with uncaught exception (group=0x41538ba8) 
01-14 12:43:11.759 5651-5651/? E/AndroidRuntime﹕ FATAL EXCEPTION: main 
    Process: com.omaxlive.myapplicationtest, PID: 5651 
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.omaxlive.myapplicationtest/com.omaxlive.myapplicationtest.MainActivity}: java.lang.NullPointerException 
      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195) 
      at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245) 
      at android.app.ActivityThread.access$800(ActivityThread.java:135) 
      at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196) 
      at android.os.Handler.dispatchMessage(Handler.java:102) 
      at android.os.Looper.loop(Looper.java:136) 
      at android.app.ActivityThread.main(ActivityThread.java:5017) 
      at java.lang.reflect.Method.invokeNative(Native Method) 
      at java.lang.reflect.Method.invoke(Method.java:515) 
      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779) 
      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595) 
      at dalvik.system.NativeStart.main(Native Method) 
    Caused by: java.lang.NullPointerException 
      at com.omaxlive.myapplicationtest.MainActivity.onCreate(MainActivity.java:25) 
      at android.app.Activity.performCreate(Activity.java:5231) 
      at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087) 
      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159) 
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245) 
            at android.app.ActivityThread.access$800(ActivityThread.java:135) 
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196) 
            at android.os.Handler.dispatchMessage(Handler.java:102) 
            at android.os.Looper.loop(Looper.java:136) 
            at android.app.ActivityThread.main(ActivityThread.java:5017) 
            at java.lang.reflect.Method.invokeNative(Native Method) 
            at java.lang.reflect.Method.invoke(Method.java:515) 
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779) 
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595) 
            at dalvik.system.NativeStart.main(Native Method) 

Answer 1

此行顯示您已經創建的按鈕是fragment_main.xml

tools:context=".MainActivity$PlaceholderFragment" 

但你發現你在activity_main.xml

按鈕

從onCreate()移動你的代碼PlaceholderFragment的onCreateView像

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

    mibtn.setOnClickListener(new View.OnClickListener() { 
     @Override 
     public void onClick(View view) { 
     Toast.makeText(getApplicationContext(),"Apretado", Toast.LENGTH_LONG).show(); 
     } 
}); 

    return rootView; 
} 

Answer 2

您是在尋找你的佈局：

setContentView (R.layout.activity_main); 

但你的佈局哪個您使用的是fragment_main.xml

所以更改setContentView(R.layout.activity_main);到setContentView(R.layout.fragment_main);

;其次，從您的java文件

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