为什么我得到 java.lang.ArithmeticException：除以零

Question

E/AndroidRuntime：致命异常：主进程：com.marsad.wallpaperapp，PID：20425 java.lang.ArithmeticException：除以零

嗨，当我单击 gif 图像以应用为动态壁纸时，大多数情况下一切正常，但有时应用程序因错误而崩溃

日志猫

E/AndroidRuntime: FATAL EXCEPTION: main Process: com.marsad.wallpaperapp, PID: 20425 java.lang.ArithmeticException: divide by zero at com.marsad.wallpaperapp.GIFWallpaperService$GIFWallpaperEngine.draw(GIFWallpaperService.java:139) at com. marsad.wallpaperapp.GIFWallpaperService$GIFWallpaperEngine.access$000(GIFWallpaperService.java:82) at com.marsad.wallpaperapp.GIFWallpaperService$GIFWallpaperEngine$1.run(GIFWallpaperService.java:111) at android.os.Handler.handleCallback(Handler.java: 873) at android.os.Handler.dispatchMessage(Handler.java:99) at android.os.Looper.loop(Looper.Z93F725A07423FE1C889F448B33D21F4 6Z:224) at android.app.ActivityThread.main(ActivityThread.java:7139) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit. java:536) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:876)

这是完整的代码

public class GIFWallpaperService extends WallpaperService {
    Context context;


    @Override
    public WallpaperService.Engine onCreateEngine() {

        Singleton b = Singleton.getInstance();
        String path = b.getPath();


        try {
            InputStream is = new FileInputStream(path);
            Movie movie = Movie.decodeStream(is);

            return new GIFWallpaperEngine(movie);

        } catch (FileNotFoundException e) {
            e.printStackTrace();
            Toast.makeText(context, "Error: " + e.getMessage(), Toast.LENGTH_SHORT).show();
            return null;
        }
        

    }


    private class GIFWallpaperEngine extends WallpaperService.Engine {

        private final int frameDuration = 20;
        private SurfaceHolder holder;
        private Movie movie;
        private boolean visible;
        private Handler handler;

        int width;
        int height;

        public GIFWallpaperEngine(Movie movie) {

            this.movie = movie;
            handler = new Handler();

        }

        @Override
        public void onCreate(SurfaceHolder surfaceHolder) {
            super.onCreate(surfaceHolder);

            this.holder = surfaceHolder;

        }

        private Runnable drawGIF = new Runnable() {
            @Override
            public void run() {
                draw();
            }
        };

        private void draw() {

            WindowManager wm = (WindowManager) getApplicationContext().getSystemService(Context.WINDOW_SERVICE);
            Display display = wm.getDefaultDisplay();
            float screenWidth = display.getWidth();
            float screenHeight = display.getHeight();

            width = (int) screenWidth;
            height = (int) screenHeight;


            if (visible) {
                Canvas canvas = holder.lockCanvas();
                canvas.save();


                canvas.scale((float) display.getWidth() / (float) movie.width(),
                        (float) display.getHeight() / (float) movie.height());
                movie.draw(canvas, 0, 0);


                canvas.restore();

                holder.unlockCanvasAndPost(canvas);
                movie.setTime((int) (System.currentTimeMillis() % movie.duration()));

                handler.removeCallbacks(drawGIF);
                handler.postDelayed(drawGIF, frameDuration);

            }

        }

        @Override
        public void onVisibilityChanged(boolean visible) {
            //super.onVisibilityChanged(visible);

            this.visible = visible;

            if (visible) {
                handler.post(drawGIF);
            } else {
                handler.removeCallbacks(drawGIF);
            }


        }

        @Override
        public void onSurfaceDestroyed(SurfaceHolder holder) {
            super.onSurfaceDestroyed(holder);
            this.visible = false;
            handler.removeCallbacks(drawGIF);
        }

        @Override
        public void onSurfaceChanged(SurfaceHolder holder, int format,
                                     int width, int height) {
            this.width = width;
            this.height = height;
            super.onSurfaceChanged(holder, format, width, height);
        }
        

        @Override
        public void onDestroy() {
            super.onDestroy();
            handler.removeCallbacks(drawGIF);

        }


    }

}

Answer 1

您可以像这样在抽奖前检查

if(movie.width() > 0 && movie.height() > 0){
        canvas.scale((float) display.getWidth() / (float) movie.width(),
                (float) display.getHeight() / (float) movie.height());
        movie.draw(canvas, 0, 0);
}else{
        //do something default which suit your application
}

Answer 2

您的例外来自以下几行：

            canvas.scale((float) display.getWidth() / (float) movie.width(),
                    (float) display.getHeight() / (float) movie.height());
            movie.draw(canvas, 0, 0);

而不是你提到的那些。

因为这些行是可能发生被零除的行。

在进行计算之前，我会确保电影 object 具有宽度/高度。