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大家好！我在女巫中有这个动态壁纸我尝试通过画布显示位图（可绘制资源是 400k 1900x1200 jpg）。它强制关闭，我不明白为什么（这是我的第一个 Android 项目）。这些是“重要”位：

    wallEngine() { // CONSTRUCTOR   <<<<<<<<<<<<<<<<<<<
                            mStartTime = SystemClock.elapsedRealtime();


                            Log.v(Logcat, "Contructor ok");

                        }
                //====================================== INIT
                        private final Runnable mDrawWall = new Runnable() { //=========== RUN
                            public void run() {
                                drawFrame();
                            }
                        };

   void drawFrame() {

                           final SurfaceHolder holder = getSurfaceHolder();                                         
                           Canvas c = null;
                           try {
                                c = holder.lockCanvas();
                                if (c != null) {
                                    // draw something
                                    updatePhysics();
                                    doDraw(c);
                                }
                            } finally {
                                if (c != null) holder.unlockCanvasAndPost(c);
                            }

                            // Reschedule the next redraw
                            mHandler.removeCallbacks(mDrawWall);
                            if (mVisible) {
                                mHandler.postDelayed(mDrawWall, 5000);
                            }
                        }


    private void doDraw(Canvas canvas) {                                                                                    
                      //backgroundImage.prepareToDraw();                                                    
                    canvas.drawBitmap(this.backgroundImage, 0, 0, null);                                                                    
                        }


public void onCreate(SurfaceHolder surfaceHolder) {

                            super.onCreate(surfaceHolder);                      surfaceHolder.setFormat(android.graphics.PixelFormat.RGBA_8888);        

                            BitmapFactory.Options options = new BitmapFactory.Options();
                            options.inPurgeable = true;

                            this.backgroundImage = BitmapFactory.decodeResource(getResources(), 
                                com.misca.livewallpapers.parang.R.drawable.a, options);

                            //backgroundImage.prepareToDraw();
                            //setTouchEventsEnabled(true);
                            Log.v(Logcat, "onCreate ok");
                        }

当我尝试在手机上运行它时出现的 logcat 错误是：

ERROR/AndroidRuntime(7722): FATAL EXCEPTION: main
ERROR/AndroidRuntime(7722): java.lang.NullPointerException
ERROR/AndroidRuntime(7722):     at android.graphics.Canvas.throwIfRecycled(Canvas.java:957)
ERROR/AndroidRuntime(7722):     at android.graphics.Canvas.drawBitmap(Canvas.java:983)
ERROR/AndroidRuntime(7722):     at com.misca.livewallpapers.parang.liveWallpaper$wallEngine.doDraw(liveWallpaper.java:115)
ERROR/AndroidRuntime(7722):     at com.misca.livewallpapers.parang.liveWallpaper$wallEngine.drawFrame(liveWallpaper.java:75)
ERROR/AndroidRuntime(7722):     at com.misca.livewallpapers.parang.liveWallpaper$wallEngine.onSurfaceChanged(liveWallpaper.java:157)
ERROR/AndroidRuntime(7722):     at android.service.wallpaper.WallpaperService$Engine.updateSurface(WallpaperService.java:590)
ERROR/AndroidRuntime(7722):     at android.service.wallpaper.WallpaperService$Engine.attach(WallpaperService.java:654)
ERROR/AndroidRuntime(7722):     at android.service.wallpaper.WallpaperService$IWallpaperEngineWrapper.executeMessage(WallpaperService.java:878)
ERROR/AndroidRuntime(7722):     at com.android.internal.os.HandlerCaller$MyHandler.handleMessage(HandlerCaller.java:61)
ERROR/AndroidRuntime(7722):     at android.os.Handler.dispatchMessage(Handler.java:99)
ERROR/AndroidRuntime(7722):     at android.os.Looper.loop(Looper.java:123)
ERROR/AndroidRuntime(7722):     at android.app.ActivityThread.main(ActivityThread.java:3848)
ERROR/AndroidRuntime(7722):     at java.lang.reflect.Method.invokeNative(Native Method)
ERROR/AndroidRuntime(7722):     at java.lang.reflect.Method.invoke(Method.java:507)
ERROR/AndroidRuntime(7722):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:841)
ERROR/AndroidRuntime(7722):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:599)
03-23 00:26:42.309: ERROR/AndroidRuntime(7722):     at dalvik.system.NativeStart.main(Native Method)

谢谢！:)

======================= 新闻：

                        private void doDraw(Canvas canvas) {                                                                               
                        //backgroundImage.prepareToDraw();                         
                        if(this.backgroundImage!=null)
                        canvas.drawBitmap(this.backgroundImage, 0, 0, null);
                        else
                        Log.v(Logcat, "null");

                    }

并且似乎位图为空。现在我正在使用 480x800 以确保没有内存问题。该应用程序不会再因 if 语句而崩溃（空黑屏）

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1 回答 1

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您是否尝试过缩放位图以适合画布？在 onSurfaceChanged 中执行此操作，这样您就会知道要使用的宽度和高度。您应该检查您的位图是否被正确解码。您的资源是 400K 并不重要——这是一个非常大的位图，可以尝试加载到内存中。你只有 16 兆的堆......那个位图大约是 9 兆（4 字节/像素 ARGB_8888）。乔治

于 2011-03-22T23:02:28.820 回答