如何解決位圖刪除中的NullPointerException。

我這裏得到一個錯誤，說，如何解決位圖刪除中的NullPointerException。

at android.graphics.Bitmap_Delegate.nativeWidth(Bitmap_Delegate.java:291) 
    at android.graphics.Bitmap.nativeWidth(Bitmap.java) 
    at android.graphics.Bitmap.getWidth(Bitmap.java:785)

的DDMS說我在ViewingWindow類，這是在INT bitmapX聲明和初始化線66得到一個錯誤：

protected void onDraw(Canvas canvas) { 
     if (canvas == null) throw new NullPointerException(); 

     Bitmap bitmap = null; 
     if (Monitor.getCurrent() == Monitor.TYPE.GREEN) bitmap = greenBitmap; 
     else bitmap = redBitmap; 

     int bitmapX = bitmap.getWidth()/2; 
     int bitmapY = bitmap.getHeight()/2; 

     int parentX = parentWidth/2; 
     int parentY = parentHeight/2; 

     int centerX = parentX - bitmapX; 
     int centerY = parentY - bitmapY; 

     matrix.reset(); 
     matrix.postTranslate(centerX, centerY); 
     canvas.drawBitmap(bitmap, matrix, paint); 
    }

爲什麼我會收到這樣的錯誤？任何幫助，高度讚賞。謝謝。

這裏是greenBitmap的初始化的變量和redBitmap：

private static Bitmap greenBitmap = null; 
    private static Bitmap redBitmap = null; 

    private static int parentWidth = 0; 
    private static int parentHeight = 0; 

    public ViewingWindow(Context context, AttributeSet attr) { 
     super(context, attr); 

     greenBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.green_icon); 
     redBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.red_icon); 
    } 

    public ViewingWindow(Context context) { 
     super(context); 

     greenBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.green_icon); 
     redBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.red_icon); 
    }

從DDMS完整的錯誤：

11-21 20:53:44.959: E/AndroidRuntime(521): FATAL EXCEPTION: main 
11-21 20:53:44.959: E/AndroidRuntime(521): java.lang.NullPointerException 
11-21 20:53:44.959: E/AndroidRuntime(521): at com.ali.nazzal.sciencefairheartrateproject.ViewingWindow.onDraw(ViewingWindow.java:66) 
11-21 20:53:44.959: E/AndroidRuntime(521): at android.view.View.draw(View.java:6740) 
11-21 20:53:44.959: E/AndroidRuntime(521): at android.view.ViewGroup.drawChild(ViewGroup.java:1640) 
11-21 20:53:44.959: E/AndroidRuntime(521): at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1367) 
11-21 20:53:44.959: E/AndroidRuntime(521): at android.view.ViewGroup.drawChild(ViewGroup.java:1638) 
11-21 20:53:44.959: E/AndroidRuntime(521): at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1367) 
11-21 20:53:44.959: E/AndroidRuntime(521): at android.view.ViewGroup.drawChild(ViewGroup.java:1638) 
11-21 20:53:44.959: E/AndroidRuntime(521): at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1367) 
11-21 20:53:44.959: E/AndroidRuntime(521): at android.view.ViewGroup.drawChild(ViewGroup.java:1638) 
11-21 20:53:44.959: E/AndroidRuntime(521): at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1367) 
11-21 20:53:44.959: E/AndroidRuntime(521): at android.view.ViewGroup.drawChild(ViewGroup.java:1638) 
11-21 20:53:44.959: E/AndroidRuntime(521): at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1367) 
11-21 20:53:44.959: E/AndroidRuntime(521): at android.view.View.draw(View.java:6743) 
11-21 20:53:44.959: E/AndroidRuntime(521): at android.widget.FrameLayout.draw(FrameLayout.java:352) 
11-21 20:53:44.959: E/AndroidRuntime(521): at com.android.internal.policy.impl.PhoneWindow$DecorView.draw(PhoneWindow.java:1842) 
11-21 20:53:44.959: E/AndroidRuntime(521): at android.view.ViewRoot.draw(ViewRoot.java:1407) 
11-21 20:53:44.959: E/AndroidRuntime(521): at android.view.ViewRoot.performTraversals(ViewRoot.java:1163) 
11-21 20:53:44.959: E/AndroidRuntime(521): at android.view.ViewRoot.handleMessage(ViewRoot.java:1727) 
11-21 20:53:44.959: E/AndroidRuntime(521): at android.os.Handler.dispatchMessage(Handler.java:99) 
11-21 20:53:44.959: E/AndroidRuntime(521): at android.os.Looper.loop(Looper.java:123) 
11-21 20:53:44.959: E/AndroidRuntime(521): at android.app.ActivityThread.main(ActivityThread.java:4627) 
11-21 20:53:44.959: E/AndroidRuntime(521): at java.lang.reflect.Method.invokeNative(Native Method) 
11-21 20:53:44.959: E/AndroidRuntime(521): at java.lang.reflect.Method.invoke(Method.java:521) 
11-21 20:53:44.959: E/AndroidRuntime(521): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868) 
11-21 20:53:44.959: E/AndroidRuntime(521): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626) 
11-21 20:53:44.959: E/AndroidRuntime(521): at dalvik.system.NativeStart.main(Native Method)

---------------- ------------ DDMS的新錯誤---------------------------------

11-21 21:49:44.699: E/AndroidRuntime(551): FATAL EXCEPTION: main 
    11-21 21:49:44.699: E/AndroidRuntime(551): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.ali.nazzal.sciencefairheartrateproject/com.ali.nazzal.sciencefairheartrateproject.Monitor}: android.view.InflateException: Binary XML file line #23: Error inflating class com.ali.nazzal.sciencefairheartrateproject.ViewingWindow 
    11-21 21:49:44.699: E/AndroidRuntime(551): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663) 
    11-21 21:49:44.699: E/AndroidRuntime(551): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679) 
    11-21 21:49:44.699: E/AndroidRuntime(551): at android.app.ActivityThread.access$2300(ActivityThread.java:125) 
    11-21 21:49:44.699: E/AndroidRuntime(551): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033) 
    11-21 21:49:44.699: E/AndroidRuntime(551): at android.os.Handler.dispatchMessage(Handler.java:99) 
    11-21 21:49:44.699: E/AndroidRuntime(551): at android.os.Looper.loop(Looper.java:123) 
    11-21 21:49:44.699: E/AndroidRuntime(551): at android.app.ActivityThread.main(ActivityThread.java:4627) 
    11-21 21:49:44.699: E/AndroidRuntime(551): at java.lang.reflect.Method.invokeNative(Native Method) 
    11-21 21:49:44.699: E/AndroidRuntime(551): at java.lang.reflect.Method.invoke(Method.java:521) 
    11-21 21:49:44.699: E/AndroidRuntime(551): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868) 
    11-21 21:49:44.699: E/AndroidRuntime(551): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626) 
    11-21 21:49:44.699: E/AndroidRuntime(551): at dalvik.system.NativeStart.main(Native Method) 
    11-21 21:49:44.699: E/AndroidRuntime(551): Caused by: android.view.InflateException: Binary XML file line #23: Error inflating class com.ali.nazzal.sciencefairheartrateproject.ViewingWindow 
    11-21 21:49:44.699: E/AndroidRuntime(551): at android.view.LayoutInflater.createView(LayoutInflater.java:503) 
    11-21 21:49:44.699: E/AndroidRuntime(551): at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:565) 
    11-21 21:49:44.699: E/AndroidRuntime(551): at android.view.LayoutInflater.rInflate(LayoutInflater.java:618) 
    11-21 21:49:44.699: E/AndroidRuntime(551): at android.view.LayoutInflater.rInflate(LayoutInflater.java:621) 
    11-21 21:49:44.699: E/AndroidRuntime(551): at android.view.LayoutInflater.rInflate(LayoutInflater.java:621) 
    11-21 21:49:44.699: E/AndroidRuntime(551): at android.view.LayoutInflater.inflate(LayoutInflater.java:407) 
    11-21 21:49:44.699: E/AndroidRuntime(551): at android.view.LayoutInflater.inflate(LayoutInflater.java:320) 
    11-21 21:49:44.699: E/AndroidRuntime(551): at android.view.LayoutInflater.inflate(LayoutInflater.java:276) 
    11-21 21:49:44.699: E/AndroidRuntime(551): at com.android.internal.policy.impl.PhoneWindow.setContentView(PhoneWindow.java:198) 
    11-21 21:49:44.699: E/AndroidRuntime(551): at android.app.Activity.setContentView(Activity.java:1647) 
    11-21 21:49:44.699: E/AndroidRuntime(551): at com.ali.nazzal.sciencefairheartrateproject.Monitor.onCreate(Monitor.java:60) 
    11-21 21:49:44.699: E/AndroidRuntime(551): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047) 
    11-21 21:49:44.699: E/AndroidRuntime(551): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627) 
    11-21 21:49:44.699: E/AndroidRuntime(551): ... 11 more 
    11-21 21:49:44.699: E/AndroidRuntime(551): Caused by: java.lang.NoSuchMethodException: ViewingWindow(Context,AttributeSet) 
    11-21 21:49:44.699: E/AndroidRuntime(551): at java.lang.Class.getMatchingConstructor(Class.java:660) 
    11-21 21:49:44.699: E/AndroidRuntime(551): at java.lang.Class.getConstructor(Class.java:477) 
    11-21 21:49:44.699: E/AndroidRuntime(551): at android.view.LayoutInflater.createView(LayoutInflater.java:475) 
    11-21 
21:49:44.699: E/AndroidRuntime(551): ... 23 more

來源

2012-11-22 Navio53

什麼是'位圖'在那一點？ 'greenBitmap'或'redBitmap'？其中之一就是'null'。 – arshajii

問題不在於'bitmap'，而是'greeenBitmap'或'redBitmap'爲空。確保它們不爲空。 –

但它似乎堆棧跟蹤說空指針發生在android.graphics.Bitmap_Delegate.nativeWidth（Bitmap_Delegate.java:291）不在ViewingWindow：66 ...你可以發佈完整的錯誤堆棧跟蹤嗎？ –

將此構造函數添加到ViewingWi ndow：

public ViewingWindow(Context context, AttributeSet attrs, int defStyle) { 
     super(context, attr, defStyle); 

     greenBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.green_icon); 
     redBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.red_icon); 
    }

來源

2012-11-22 04:43:18

我做到了，錯誤發生了變化。它不再引用第66行。它不能使課堂膨脹。我會把這個錯誤放在我的問題中。 – Navio53

@ Navio53你**替換了構造函數而不是添加它嗎？在新的錯誤中，它說它找不到構造函數'ViewingWindow（Context context，AttributeSet attrs）' –

Ya，我去了並且添加了構造函數而沒有替換原來的，並且我得到了與第一組錯誤相同的錯誤我張貼在我的問題。 – Navio53

如何解決位圖刪除中的NullPointerException。

回答

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