Android SDK中自定義鍵盤，設置背景和文本顏色：一個鍵

Question

這裏是我的代碼：

公共類CustomKeyboardView擴展KeyboardView {

public CustomKeyboardView(Context context, AttributeSet attrs) { 
     super(context, attrs); 
    } 


    @Override 
    public void onDraw(Canvas canvas) { 
     super.onDraw(canvas); 

     Paint paintBackground = new Paint(); 
     paintBackground.setTextAlign(Paint.Align.CENTER); 
     paintBackground.setTextSize(48); 
     paintBackground.setColor(Color.YELLOW); 


     List<Key> keys = getKeyboard().getKeys(); 
     for(Key key: keys) { 
      if(key.label != null && key.codes[0] == 110) 
       canvas.drawRect(key.x, key.y, key.x+key.width, key.y+key.height, paintBackground); 

       paintBackground.setColor(Color.WHITE); 
       canvas.drawText(key.label.toString(), key.x + (key.width/2), 
         key.y + (key.height/2), paintBackground); 

     } 
    } 


} 

奇怪的是，如果我註釋掉帆布drawRect中或帆布的drawText，另一個工作正常，但如果我離開他們都在，我得到這個錯誤：

 FATAL EXCEPTION: main Process: com.alpha.alphaproto, PID: 6540 
    java.lang.NullPointerException 
     at com.alpha.alphaproto.CustomKeyboardView.onDraw(CustomKeyboardView.java:48) 
     at android.view.View.draw(View.java:14465) 
     at android.view.View.getDisplayList(View.java:13362) 
     at android.view.View.getDisplayList(View.java:13404) 
     at android.view.View.draw(View.java:14182) 
     at android.view.ViewGroup.drawChild(ViewGroup.java:3103) 
     at android.view.ViewGroup.dispatchDraw(ViewGroup.java:2940) 
     at android.view.View.getDisplayList(View.java:13357) 
     at android.view.View.getDisplayList(View.java:13404) 
     at android.view.View.draw(View.java:14182) 
     at android.view.ViewGroup.drawChild(ViewGroup.java:3103) 
     at android.view.ViewGroup.dispatchDraw(ViewGroup.java:2940) 
     at android.view.View.draw(View.java:14468) 
     at android.widget.FrameLayout.draw(FrameLayout.java:472) 
     at android.view.View.getDisplayList(View.java:13362) 
     at android.view.View.getDisplayList(View.java:13404) 
     at android.view.View.draw(View.java:14182) 
     at android.view.ViewGroup.drawChild(ViewGroup.java:3103) 
     at android.view.ViewGroup.dispatchDraw(ViewGroup.java:2940) 
     at android.view.View.getDisplayList(View.java:13357) 
     at android.view.View.getDisplayList(View.java:13404) 
     at android.view.View.draw(View.java:14182) 
     at android.view.ViewGroup.drawChild(ViewGroup.java:3103) 
     at android.view.ViewGroup.dispatchDraw(ViewGroup.java:2940) 
     at android.view.View.draw(View.java:14468) 
     at android.widget.FrameLayout.draw(FrameLayout.java:472) 
     at com.android.internal.policy.impl.PhoneWindow$DecorView.draw(PhoneWindow.java:2326) 
     at android.view.View.getDisplayList(View.java:13362) 
     at android.view.View.getDisplayList(View.java:13404) 
     at android.view.HardwareRenderer$GlRenderer.buildDisplayList(HardwareRenderer.java:1570) 
     at android.view.HardwareRenderer$GlRenderer.draw(HardwareRenderer.java:1449) 
     at android.view.ViewRootImpl.draw(ViewRootImpl.java:2377) 
     at android.view.ViewRootImpl.performDraw(ViewRootImpl.java:2249) 
     at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1879) 
     at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:996) 
     at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5600) 
     at android.view.Choreographer$CallbackRecord.run(Choreographer.java:761) 
     at android.view.Choreographer.doCallbacks(Choreographer.java:574) 
     at android.view.Choreographer.doFrame(Choreographer.java:544) 
     at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:747) 
     at android.os.Handler.handleCallback(Handler.java:733) 
     at android.os.Handler.dispatchMessage(Handler.java:95) 
     at android.os.Looper.loop(Looper.java:136) 
     at android.app.ActivityThread.main(ActivityThread.java:5001) 
     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:785) 
     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601) 
     at dalvik.system.NativeStart.main(Native Method 

我大惑不解。任何幫助將非常感激。

Answer 1

這是修改。上述代碼在任何情況下都不起作用。下面是代碼，其中drawText或drawRect工作，但不在一起：

Paint paintBackground = new Paint(); 
    paintBackground.setTextAlign(Paint.Align.CENTER); 
    paintBackground.setTextSize(48); 
    paintBackground.setColor(Color.YELLOW); 

    Paint paint = new Paint(); 
    paint.setTextAlign(Paint.Align.CENTER); 
    paint.setTextSize(48); 
    paint.setColor(Color.BLACK); 

    List<Key> keys = getKeyboard().getKeys(); 
    for(Key key: keys) { 
     if(key.label != null && key.codes[0] == 110) 
      //canvas.drawText(key.label.toString(), key.x + (key.width/2), key.y + 25, paint); 
      canvas.drawRect(key.x, key.y, key.x+key.width, key.y+key.height, paintBackground); 
      canvas.drawText(key.label.toString(), key.x + (key.width/2), 
        key.y + (key.height/2), paint); 

    } 

Answer 2

我修好了。有一個缺失的括號。