在Android模拟器中停止应用程序

我完全不熟悉java，所以我已经开始制作应用程序来通过添加和减去按钮来查找TOTAL。我在FRAGMENT_MAIN.XML中定义了按钮和文本视图，并在主要activity.JAVA中定义了它们的功能。在主activity.java中定义按钮的功能后，我的程序中出现logcat错误，应用程序在android模拟器中不幸停住。我使用的是android sdk版本22.6.4，eclipse ide for java develpers版本是2.0.2.20140224-0000和eclipse平台版本是4.3.2.v2.140221-1852。在Android模拟器中停止应用程序

我MainActivity.java

package com.counterehr.abhi; 

public class MainActivity extends ActionBarActivity { 

    int counter; 
    Button add, sub; 
    TextView display; 

    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main); 
     counter = 0; 
     add = (Button) findViewById(R.id.bAdd); 
     sub = (Button) findViewById(R.id.bSub); 
     display = (TextView) findViewById(R.id.tvDisplay); 
     add.setOnClickListener(new View.OnClickListener() { 

      @Override 
      public void onClick(View v) { 
       // TODO Auto-generated method stub 
       counter++; 
       display.setText("Your total is " + counter); 
      } 
     }); 
    sub.setOnClickListener(new View.OnClickListener() { 

      @Override 
      public void onClick(View v) { 
       // TODO Auto-generated method stub 
       counter--; 
       display.setText("Your total is " + counter); 
      } 
     }); 

    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. 
     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; 
     } 
    } 

}

和FRAGMENT_MAIN.XM L是

FRAGMENT_MAIN.XML 

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    xmlns:tools="http://schemas.android.com/tools" 
    android:layout_width="fill_parent" 
    android:layout_height="fill_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.counterehr.abhi.MainActivity$PlaceholderFragment" > 

    <TextView 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:text="Your total is 0" 
     android:textSize="45sp" 
     android:layout_gravity="center" 
     android:gravity="center" 
     android:id="@+id/tvDisplay"/> 

     <Button 
      android:id="@+id/bAdd" 
      android:layout_width="250dp" 
      android:layout_height="wrap_content" 
      android:layout_below="@+id/tvDisplay" 
      android:layout_centerHorizontal="true" 
      android:layout_marginTop="46dp" 
      android:text="Add one" 
      android:textSize="20sp" /> 

     <Button 
      android:id="@+id/bSub" 
      android:layout_width="250dp" 
      android:layout_height="wrap_content" 
      android:layout_alignLeft="@+id/bAdd" 
      android:layout_centerVertical="true" 
      android:text="Subtract one" 
      android:textSize="20sp" /> 

</RelativeLayout>

上运行我得到的logcat错误的应用程序。

logcat的错误

07-01 18:16:17.963: E/Trace(833): error opening trace file: No such file or directory (2) 
    07-01 18:16:19.675: D/dalvikvm(833): GC_FOR_ALLOC freed 80K, 9% free 2419K/2644K, paused 356ms, total 356ms 
    07-01 18:16:19.704: I/dalvikvm-heap(833): Grow heap (frag case) to 3.415MB for 960016-byte allocation 
    07-01 18:16:19.802: D/dalvikvm(833): GC_FOR_ALLOC freed 1K, 7% free 3355K/3584K, paused 97ms, total 97ms 
    07-01 18:16:20.002: D/dalvikvm(833): GC_CONCURRENT freed <1K, 7% free 3355K/3584K, paused 9ms+33ms, total 201ms 
    07-01 18:16:20.382: D/dalvikvm(833): GC_CONCURRENT freed <1K, 6% free 3779K/4004K, paused 5ms+4ms, total 52ms 
    07-01 18:16:20.543: D/AndroidRuntime(833): Shutting down VM 
    07-01 18:16:20.543: W/dalvikvm(833): threadid=1: thread exiting with uncaught exception (group=0x40a71930) 
    07-01 18:16:20.583: E/AndroidRuntime(833): FATAL EXCEPTION: main 
    07-01 18:16:20.583: E/AndroidRuntime(833): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.counterehr.abhi/com.counterehr.abhi.MainActivity}: java.lang.NullPointerException 
    07-01 18:16:20.583: E/AndroidRuntime(833): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180) 
    07-01 18:16:20.583: E/AndroidRuntime(833): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230) 
    07-01 18:16:20.583: E/AndroidRuntime(833): at android.app.ActivityThread.access$600(ActivityThread.java:141) 
    07-01 18:16:20.583: E/AndroidRuntime(833): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234) 
    07-01 18:16:20.583: E/AndroidRuntime(833): at android.os.Handler.dispatchMessage(Handler.java:99) 
    07-01 18:16:20.583: E/AndroidRuntime(833): at android.os.Looper.loop(Looper.java:137) 
    07-01 18:16:20.583: E/AndroidRuntime(833): at android.app.ActivityThread.main(ActivityThread.java:5041) 
    07-01 18:16:20.583: E/AndroidRuntime(833): at java.lang.reflect.Method.invokeNative(Native Method) 
    07-01 18:16:20.583: E/AndroidRuntime(833): at java.lang.reflect.Method.invoke(Method.java:511) 
    07-01 18:16:20.583: E/AndroidRuntime(833): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793) 
    07-01 18:16:20.583: E/AndroidRuntime(833): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560) 
    07-01 18:16:20.583: E/AndroidRuntime(833): at dalvik.system.NativeStart.main(Native Method) 
    07-01 18:16:20.583: E/AndroidRuntime(833): Caused by: java.lang.NullPointerException 
    07-01 18:16:20.583: E/AndroidRuntime(833): at com.counterehr.abhi.MainActivity.onCreate(MainActivity.java:33) 
    07-01 18:16:20.583: E/AndroidRuntime(833): at android.app.Activity.performCreate(Activity.java:5104) 
    07-01 18:16:20.583: E/AndroidRuntime(833): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080) 
    07-01 18:16:20.583: E/AndroidRuntime(833): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144) 
    07-01 18:16:20.583: E/AndroidRuntime(833): ... 11 more 
    07-01 18:16:23.873: I/Process(833): Sending signal. PID: 833 SIG: 9

请！有人帮我解决这个问题，我尝试了所有可能的事情，但没有得到解决方案。

来源

2014-07-02 user3794867

的“轻度精”版这是因为你混合片段和活动。我会找到你应该看起来像什么样的基本布局... sec – EpicPandaForce

[NullPointerException访问onCreate（）中的视图的可能重复（http://stackoverflow.com/questions/23653778/nullpointerexception-accessing-views- in-oncreate） – laalto

问题是，您正在混合碎片和活动，因此，即使这些视图显示在碎片中，也是在活动中处理事件。基本上你打算在Activity中有一个FrameLayout，就是这样 - 逻辑在Fragment中处理。

一个例子如下：

public class ContainerActivity extends ActionBarActivity 
{ 
    @Override 
    public void onCreate(Bundle saveInstanceState) 
    { 
     super.onCreate(saveInstanceState); 
     this.setContentView(R.layout.activity_container); 
     getSupportActionBar().setDisplayHomeAsUpEnabled(true); 
     if (saveInstanceState == null) 
     {    
      getSupportFragmentManager().beginTransaction() 
       .add(R.id.activity_container_container, new ExampleFragment()) 
       .addToBackStack(null) 
      .commit(); 
     } 
     getSupportFragmentManager().addOnBackStackChangedListener(new OnBackStackChangedListener() 
     { 
      public void onBackStackChanged() 
      { 
       int backCount = getSupportFragmentManager().getBackStackEntryCount(); 
       if (backCount == 0) 
       { 
        finish(); 
       } 
      } 
     }); 
    } 
}

activity_container.xml：

<?xml version="1.0" encoding="utf-8"?> 
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" 
    android:orientation="vertical" > 

    <FrameLayout 
     android:id="@+id/activity_container_container" 
     android:layout_width="match_parent" 
     android:layout_height="match_parent" /> 

</RelativeLayout>

ExampleFragment：

public class ExampleFragment extends Fragment implements View.OnClickListener 
{ 
    private Button btnOne; 
    private Button btnTwo; 
    private Button btnThree; 

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

     btnOne = (Button) rootView.findViewById(R.id.example_button_one); 
     btnTwo = (Button) rootView.findViewById(R.id.example_button_two); 
     btnThree = (Button) rootView.findViewById(R.id.example_button_three); 

     btnOne.setOnClickListener(this); 
     btnTwo.setOnClickListener(this); 
     btnThree.setOnClickListener(this); 
     return rootView; 
    } 

    @Override 
    public void onClick(View v) 
    { 
     if (btnOne == v) 
     { 
      Toast.makeText(getActivity(), "One.", Toast.LENGTH_LONG).show(); 
     } 
     else if (btnTwo == v) 
     { 
      Toast.makeText(getActivity(), "Two.", Toast.LENGTH_LONG).show(); 
     } 
     else if (btnThree == v) 
     { 
      Toast.makeText(getActivity(), "Three.", Toast.LENGTH_LONG).show(); 
     } 
    } 
}

fragment_example.xml：

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

     <Button 
      android:id="@+id/example_button_one" 
      android:layout_width="match_parent" 
      android:layout_height="wrap_content" 
      android:layout_alignParentTop="true" 
      android:layout_centerHorizontal="true" 
      android:layout_marginTop="30dp" 
      android:text="@string/hello" 
      android:layout_marginLeft="20dp" 
      android:layout_marginRight="20dp"/> 

     <Button 
      android:id="@+id/example_button_two" 
      android:layout_width="wrap_content" 
      android:layout_height="wrap_content" 
      android:layout_alignLeft="@+id/example_button_one" 
      android:layout_alignRight="@+id/example_button_one" 
      android:layout_below="@+id/example_button_one" 
      android:layout_marginTop="30dp" 
      android:text="@string/hello" /> 

     <Button 
      android:id="@+id/example_button_three" 
      android:layout_width="wrap_content" 
      android:layout_height="wrap_content" 
      android:layout_alignLeft="@+id/example_button_two" 
      android:layout_alignRight="@+id/example_button_two" 
      android:layout_below="@+id/example_button_two" 
      android:layout_marginTop="30dp" 
      android:text="@string/hello" /> 

</RelativeLayout>

Android系统的Manifest.xml：

<?xml version="1.0" encoding="utf-8"?> 
<manifest xmlns:android="http://schemas.android.com/apk/res/android" 
    package="com.example" 
    android:versionCode="1" 
    android:versionName="1.0" > 

    <uses-sdk 
     android:minSdkVersion="8" 
     android:targetSdkVersion="19" /> 
    <application 
     android:allowBackup="true" 
     android:icon="@drawable/ic_launcher" 
     android:label="@string/app_name" 
     android:theme="@style/AppTheme" > 
     <activity 
      android:name="com.example.ContainerActivity" 
      android:label="@string/app_name"> 
      <intent-filter> 
       <action android:name="android.intent.action.MAIN" /> 
       <category android:name="android.intent.category.LAUNCHER" /> 
      </intent-filter> 
     </activity> 
    </application> 

</manifest>

，这应该是一个有效的例子，它说明了如何使用一个活动来显示片段，并处理该分段的事件。它目前并不显示Fragment如何与Activity进行通信以更改为另一个Fragment，这是通过接口完成的，您可以将这个变量存储在onAttach（）回调方法中。

但我没有包括以及在NullPointerException accessing views in onCreate()

来源

2014-07-02 09:13:54 EpicPandaForce

另外，这个使用了AppCompat的ActionBarActivity。如果你不需要一个ActionBar，那么从FragmentActivity扩展。 – EpicPandaForce

我添加了额外的细节，并删除了http://stackoverflow.com/questions/23653778/nullpointerexception-accessing-views-in-oncreate – EpicPandaForce

nope的app_compat依赖项，先生上面的解决方案没有解决。仍然显示它的应用程序已停止。你可以用简单的话来解释一下这个问题。我是新来的Java所以我会非常感谢你，如果你请帮我解决这个问题。我不想在这个初始点停止学习java。请...请帮助 – user3794867

在Android模拟器中停止应用程序

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