空指针异常与imageView

'giraffe.getX（）'上的空指针异常，不知道为什么，我必须声明错误？下面是代码的XML和栈跟踪错误是在线路36上DX = X- giraffe.getX（）空指针异常与imageView

public class MainGameActivity extends Activity implements OnTouchListener { 

float x,y,dx,dy; 
ImageView giraffe; 
private static final String ONTOUCH_TAG = "Entered onTouch()"; 


@Override 
protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     this.requestWindowFeature(Window.FEATURE_NO_TITLE); 
     setContentView(R.layout.activity_main_game); 
     ImageView giraffe = (ImageView)findViewById(R.id.giraffe); 
     giraffe.setOnTouchListener(this); 
} 


public boolean onTouch(View v, MotionEvent me){ 

    if(me.getAction() == MotionEvent.ACTION_DOWN){ 
     Log.d(ONTOUCH_TAG, "ONTOUCH"); 
     x = me.getX(); 
     y = me.getY(); 
     dx = x - giraffe.getX(); 
     dy = y - giraffe.getY(); 
    } 

    if(me.getAction() == MotionEvent.ACTION_MOVE) 
    { 
     giraffe.setX(me.getX()-dx); 
     giraffe.setY(me.getY()-dy); 
    } 

    return true; 
} 

@Override 
public boolean onCreateOptionsMenu(Menu menu) { 
    // Inflate the menu; this adds items to the action bar if it is present. 
    getMenuInflater().inflate(R.menu.activity_main_game, menu); 
    return true; 
} 

}

布局文件：

<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" 
tools:context=".MainGameActivity" > 

<ImageView 
    android:id="@+id/giraffe" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:layout_alignParentBottom="true" 
    android:layout_centerHorizontal="true" 
    android:layout_marginBottom="58dp" 
    android:contentDescription="@string/giraffe" 
    android:src="@drawable/giraffeicon" /> 

</RelativeLayout>

堆栈跟踪

07-07 14:47:49.606: E/AndroidRuntime(1229): FATAL EXCEPTION: main 
07-07 14:47:49.606: E/AndroidRuntime(1229): java.lang.NullPointerException 
07-07 14:47:49.606: E/AndroidRuntime(1229):  at com.SandBProductions.fallingobjects.MainGameActivity.onTouch(MainGameActivity.java:36) 
07-07 14:47:49.606: E/AndroidRuntime(1229):  at android.view.View.dispatchTouchEvent(View.java:7234) 
07-07 14:47:49.606: E/AndroidRuntime(1229):  at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2174) 
07-07 14:47:49.606: E/AndroidRuntime(1229):  at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1875) 
07-07 14:47:49.606: E/AndroidRuntime(1229):  at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2174) 
07-07 14:47:49.606: E/AndroidRuntime(1229):  at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1875) 
07-07 14:47:49.606: E/AndroidRuntime(1229):  at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2174) 
07-07 14:47:49.606: E/AndroidRuntime(1229):  at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1875) 
07-07 14:47:49.606: E/AndroidRuntime(1229):  at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2174) 
07-07 14:47:49.606: E/AndroidRuntime(1229):  at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1875) 
07-07 14:47:49.606: E/AndroidRuntime(1229):  at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:1953) 
07-07 14:47:49.606: E/AndroidRuntime(1229):  at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1405) 
07-07 14:47:49.606: E/AndroidRuntime(1229):  at android.app.Activity.dispatchTouchEvent(Activity.java:2410) 
07-07 14:47:49.606: E/AndroidRuntime(1229):  at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:1901) 
07-07 14:47:49.606: E/AndroidRuntime(1229):  at android.view.View.dispatchPointerEvent(View.java:7419) 
07-07 14:47:49.606: E/AndroidRuntime(1229):  at android.view.ViewRootImpl.deliverPointerEvent(ViewRootImpl.java:3220) 
07-07 14:47:49.606: E/AndroidRuntime(1229):  at android.view.ViewRootImpl.deliverInputEvent(ViewRootImpl.java:3165) 
07-07 14:47:49.606: E/AndroidRuntime(1229):  at android.view.ViewRootImpl.doProcessInputEvents(ViewRootImpl.java:4292) 
07-07 14:47:49.606: E/AndroidRuntime(1229):  at android.view.ViewRootImpl.enqueueInputEvent(ViewRootImpl.java:4271) 
07-07 14:47:49.606: E/AndroidRuntime(1229):  at android.view.ViewRootImpl$WindowInputEventReceiver.onInputEvent(ViewRootImpl.java:4363) 
07-07 14:47:49.606: E/AndroidRuntime(1229):  at android.view.InputEventReceiver.dispatchInputEvent(InputEventReceiver.java:179) 
07-07 14:47:49.606: E/AndroidRuntime(1229):  at android.os.MessageQueue.nativePollOnce(Native Method) 
07-07 14:47:49.606: E/AndroidRuntime(1229):  at android.os.MessageQueue.next(MessageQueue.java:125) 
07-07 14:47:49.606: E/AndroidRuntime(1229):  at android.os.Looper.loop(Looper.java:124) 
07-07 14:47:49.606: E/AndroidRuntime(1229):  at android.app.ActivityThread.main(ActivityThread.java:5039) 
07-07 14:47:49.606: E/AndroidRuntime(1229):  at java.lang.reflect.Method.invokeNative(Native Method) 
07-07 14:47:49.606: E/AndroidRuntime(1229):  at java.lang.reflect.Method.invoke(Method.java:511) 
07-07 14:47:49.606: E/AndroidRuntime(1229):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793) 
07-07 14:47:49.606: E/AndroidRuntime(1229):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560) 
07-07 14:47:49.606: E/AndroidRuntime(1229):  at dalvik.system.NativeStart.main(Native Method)

来源

2013-07-07 Brian

ImageView长颈鹿为空：

ImageView giraffe; 



@Override 
protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     giraffe = (ImageView)findViewById(R.id.giraffe); 

}

来源

2013-07-07 14:56:50 user1888162

非常感谢你......在这样一个简单的修复中凝视的方式太长-_- – Brian

你已经定义了长颈鹿两次（一次全局，一次在onCreate）：

ImageView giraffe =（ImageView）findViewById（R.id.giraffe）;

从此语句中删除ImageView，它将工作。

来源

2013-07-07 14:57:20 IanB

空指针异常与imageView

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