Question

我正在尝试在画布上绘制位图图像。但是在这样做的时候，我得到了以下指定的异常。

10-10 11:29:18.592: A/libc(20706): Fatal signal 11 (SIGSEGV), code 1, fault addr 0xc0 in tid 20706 (apcanvasexample)

以下是我的代码。

 public class MapView extends View implements IAsyncResponse {
    private Path path;
    private Paint paint;

    private URL url;

    private Bitmap bmp;
    private Canvas canvas;

    public MapView(Context context, AttributeSet attrs) {
        super(context, attrs);
        path = new Path();
        paint = new Paint();
        paint.setStyle(Paint.Style.STROKE);
        paint.setColor(Color.RED);
        paint.setStrokeWidth(10);
        path.moveTo(0, 0);

    }

    @SuppressLint("DrawAllocation")
    @Override
    public void onDraw(Canvas canvas) {
        this.canvas = canvas;

            path.lineTo(currentX, currentY);
            canvas.drawPath(path, paint);

        new DownloadImageTask(canvas, this)
                .execute("http://<ip>:<port>/map/download/image?imageType=jpg&mapId=1");
    }

    private class DownloadImageTask extends AsyncTask<String, Void, Bitmap> {
        IAsyncResponse delegate;
        Canvas canvas;

        public DownloadImageTask(Canvas canvas, IAsyncResponse delegate) {
            this.canvas = canvas;
            this.delegate = delegate;
        }

        protected Bitmap doInBackground(String... urls) {
            String urldisplay = urls[0];
            Bitmap mIcon11 = null;
            try {
                InputStream in = new java.net.URL(urldisplay).openStream();
                mIcon11 = BitmapFactory.decodeStream(in);
            } catch (Exception e) {
                Log.e("Error", e.getMessage());
                e.printStackTrace();
            }
            return mIcon11;
        }

        protected void onPostExecute(Bitmap result) {
            delegate.processFinished(result);
        }
    }

    @Override
    public void processFinished(Bitmap bmp) {
        canvas.drawBitmap(bmp, new Rect(100,100,150,150), new Rect(0,0,50,50) , null);
    }

}

Answer 1

public class MapView
        extends View
        implements IAsyncResponse {

    public MapView(Context context) {
        super(context);
        init();
    }

    public MapView(
            Context context,
            AttributeSet attrs) {
        super(context, attrs);
        init();

    }

    public MapView(
            Context context,
            AttributeSet attrs,
            int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init();
    }

    private Path path;
    private Paint paint;

    private URL url;

    private Bitmap bmp;

    // use common init method for initialization, which is called from all the constructors
    void init() {
        path = new Path();
        paint = new Paint();
        paint.setStyle(Paint.Style.STROKE);
        paint.setColor(Color.RED);
        paint.setStrokeWidth(10);
        path.moveTo(0, 0);

        // start the downloader task only once and not within onDraw callback
        // please note that, reference to canvas is not hold
        new DownloadImageTask(this).execute("my/image/url");
    }

    @Override
    public void onDraw(Canvas canvas) {
        // all your other drawing logic goes here
        if (null != bmp) {
            canvas.drawBitmap(bmp, new Rect(100, 100, 150, 150), new Rect(0, 0, 50, 50), null);
        }
    }

    private class DownloadImageTask
            extends AsyncTask<String, Void, Bitmap> {
        IAsyncResponse delegate;

        public DownloadImageTask(
                IAsyncResponse delegate) {
            this.delegate = delegate;
        }

        protected Bitmap doInBackground(String... urls) {
            String urldisplay = urls[0];
            Bitmap mIcon11 = null;
            try {
                InputStream in = new java.net.URL(urldisplay).openStream();
                mIcon11 = BitmapFactory.decodeStream(in);
            } catch (Exception e) {
                Log.e("Error", e.getMessage());
                e.printStackTrace();
            }
            return mIcon11;
        }

        protected void onPostExecute(Bitmap result) {
            // you probably don't even need delegate. But I have kept it for consistency.
            // alternatively you can remove this interface and do - 
            //          MapView.this.bmp = bmp;
            //          invalidate();

            delegate.processFinished(result);
        }
    }

    @Override
    public void processFinished(Bitmap bmp) {
        this.bmp = bmp;
        invalidate();
    }

}

Answer 2

您需要禁用此视图的硬件加速。

yourview.setLayerType(View.LAYER_TYPE_SOFTWARE, null);

https://developer.android.com/guide/topics/graphics/hardware-accel.html#controlling

尝试在画布上绘制位图时，tid 20706中的致命信号11（SIGSEGV），代码1，故障地址0xc0

2 个答案: