NullPointerException FlipView Android

Question

我正在寫一個簡單的手電筒應用程序，我希望能夠從一個視圖（flashOn）移動到另一個（flashOff）。我看到一篇關於使用FlipView的文章，這是最好的方法嗎？ （我不想用於活動..）我很瞭解這一點，所以請糾正我！我不斷收到關於lightBtnOn.setOnClickListener(new ImageButton.OnClickListener(){

這裏一個NullPointerException是活動類：

@Override 
public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.no_torch); 

    ImageButton lightBtnOn = (ImageButton) findViewById(R.id.light_on); 
    ImageButton lightBtnOff = (ImageButton) findViewById(R.id.light_off); 


    final ViewFlipper viewFlipper = (ViewFlipper)findViewById(R.id.viewflipper); 
    final Animation animFlipInNext = AnimationUtils.loadAnimation(this, R.anim.flipinnext); 
    final Animation animFlipOutNext = AnimationUtils.loadAnimation(this, R.anim.flipoutnext); 
    final Animation animFlipInPrevious = AnimationUtils.loadAnimation(this, R.anim.flipinprevious); 
    final Animation animFlipOutPrevious = AnimationUtils.loadAnimation(this, R.anim.flipoutprevious); 

    lightBtnOn.setOnClickListener(new ImageButton.OnClickListener(){ 

      @Override 
      public void onClick(View v) { 
       viewFlipper.setInAnimation(animFlipInNext); 
       viewFlipper.setOutAnimation(animFlipOutNext); 
       viewFlipper.showNext(); 
      }}); 

    lightBtnOff.setOnClickListener(new ImageButton.OnClickListener(){ 

@Override 
public void onClick(View v) { 
    viewFlipper.setInAnimation(animFlipInPrevious); 
    viewFlipper.setOutAnimation(animFlipOutPrevious); 
    viewFlipper.showPrevious(); 
}}); 

這裏是我的XML：

<?xml version="1.0" encoding="utf-8"?> 
<RelativeLayout 
    android:layout_width="fill_parent" 
    android:layout_height="fill_parent" 
    android:orientation="vertical" 
    xmlns:android="http://schemas.android.com/apk/res/android"> 
<LinearLayout 
    android:id="@+id/linearLayout" 
    android:orientation="vertical" 
    android:layout_width="fill_parent" 
    android:layout_height="fill_parent" > 
     </LinearLayout> 

<ViewFlipper 
    android:id="@+id/viewflipper" 
    android:layout_width="fill_parent" 
    android:layout_height="fill_parent" 
    android:autoStart= "true"> 
    <RelativeLayout 
     android:layout_width="fill_parent" 
     android:layout_height="fill_parent" 
     android:orientation="vertical"> 
     <ImageButton 
       android:id="@+id/light_on" 
       android:layout_width="wrap_content" 
       android:layout_height="wrap_content" 
       android:background="@drawable/light_on" 
       android:layout_centerInParent="true"/> 

    <!-- To be used With Strobe Light Feature 
     <SeekBar android:id="@+id/seek" 
      android:layout_width="fill_parent" 
      android:layout_height="wrap_content" 
      android:max="20" 
      android:progress="0" /> --> 

     <TextView 
      android:id="@+id/editText1" 
      android:layout_width="wrap_content" 
      android:layout_height="wrap_content" 
      android:layout_below="@+id/light_on" 
      android:layout_centerHorizontal="true" 
      android:layout_marginTop="35dp" 
      android:text="@string/lightOff" /> 
    </RelativeLayout> 
    <RelativeLayout 
     android:layout_width="fill_parent" 
     android:layout_height="fill_parent" 
     android:orientation="vertical"> 
     <ImageButton 
      android:id="@+id/light_off" 
      android:layout_width="wrap_content" 
      android:layout_height="wrap_content" 
      android:background="@drawable/light_off" 
      android:layout_centerInParent="true"/> 

     <TextView 
      android:id="@+id/editText1" 
      android:layout_width="wrap_content" 
      android:layout_height="wrap_content" 
      android:layout_below="@+id/light_off" 
      android:layout_centerHorizontal="true" 
      android:layout_marginTop="35dp" 
      android:text="@string/lightOn" /> 
    </RelativeLayout> 

</ViewFlipper> 

這裏是NullPointerException異常logcat的結果：

11-26 18:02:31.501: E/AndroidRuntime(22663): FATAL EXCEPTION: main 
11-26 18:02:31.501: E/AndroidRuntime(22663): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.marshall.meadows182/com.marshall.meadows182.LightTorch}: java.lang.NullPointerException 
11-26 18:02:31.501: E/AndroidRuntime(22663): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1821) 
11-26 18:02:31.501: E/AndroidRuntime(22663): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1842) 
11-26 18:02:31.501: E/AndroidRuntime(22663): at android.app.ActivityThread.access$1500(ActivityThread.java:132) 
11-26 18:02:31.501: E/AndroidRuntime(22663): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1038) 
11-26 18:02:31.501: E/AndroidRuntime(22663): at android.os.Handler.dispatchMessage(Handler.java:99) 
11-26 18:02:31.501: E/AndroidRuntime(22663): at android.os.Looper.loop(Looper.java:143) 
11-26 18:02:31.501: E/AndroidRuntime(22663): at android.app.ActivityThread.main(ActivityThread.java:4263) 
11-26 18:02:31.501: E/AndroidRuntime(22663): at java.lang.reflect.Method.invokeNative(Native Method) 
11-26 18:02:31.501: E/AndroidRuntime(22663): at java.lang.reflect.Method.invoke(Method.java:507) 
11-26 18:02:31.501: E/AndroidRuntime(22663): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839) 
11-26 18:02:31.501: E/AndroidRuntime(22663): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597) 
11-26 18:02:31.501: E/AndroidRuntime(22663): at dalvik.system.NativeStart.main(Native Method) 
11-26 18:02:31.501: E/AndroidRuntime(22663): Caused by: java.lang.NullPointerException 
11-26 18:02:31.501: E/AndroidRuntime(22663): at com.marshall.meadows182.LightTorch.onCreate(LightTorch.java:43) 
11-26 18:02:31.501: E/AndroidRuntime(22663): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1072) 
11-26 18:02:31.501: E/AndroidRuntime(22663): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1785) 
11-26 18:02:31.501: E/AndroidRuntime(22663): ... 11 more 

Answer 1

嘗試「新的OnClickListener」，而不是「新ImageButton.OnClickListener」