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

Question

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

嗨，当我点击 gif 图像作为动态壁纸应用时，大多数一切都很好，但有时应用程序崩溃并出现错误

日志猫

E/Android运行时：致命异常：main 进程： com.marsad.wallpaperapp， PID： 20425 java.lang.ArithmeticException： 除以零 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$1.run(GIFWallpaperService.java：111( at android.os.Handler.handleCallback(Handler.java：873( at android.os.Handler.dispatchMessage(Handler.java：99( at android.os.Looper.loop(Looper.java：224( at android.app.ActivityThread.main(ActivityThread.java：7139( at java.lang.reflect.Method.invoke(Native Method( at com.android.internal.os.RuntimeInit$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

你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

您的异常来自以下行：

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。

因为这些线是可能发生除以零的线。

在进行计算之前，我会确保电影对象具有宽度/高度。