Question

我对android中的画布有一点小问题。我正在编写扫描仪。扫描仪的功能完美。但我的目标是在扫描仪中绘制一些矩形，它看起来像一个真正的扫描仪。这有一半的时间。

如果我第一次启动应用程序，一切都很好。所有矩形和扫描仪线都绘制在中间。但是，如果我关闭应用程序并重新启动它，则缺少矩形和线条。

我有方法onDraw，我知道应用程序正在调用它（两次都是）。我检查了所有变量（例如：首先启动，重启）。如果我关闭设备电源并启动应用程序，它也可以正常工作。

也许我必须把元素带到前面？

感谢。

@SuppressLint("DrawAllocation")
    @Override
    public void onDraw(Canvas canvas) {

        setWillNotDraw(false);
        super.onDraw(canvas);

        if (cameraManager == null) {
            return; // not ready yet, early draw before done configuring
        }
        Rect frame = cameraManager.getFramingRect();
        Rect previewFrame = cameraManager.getFramingRectInPreview();

        if (frame == null || previewFrame == null) {
            return;
        }
        int width = canvas.getWidth();
        int height = canvas.getHeight();

        // Draw the exterior (i.e. outside the framing rect) darkened
        paint.setColor(resultBitmap != null ? resultColor : maskColor);
        canvas.drawRect(0, 0, width, frame.top, paint);
        canvas.drawRect(0, frame.top, frame.left, frame.bottom + 1, paint);
        canvas.drawRect(frame.right + 1, frame.top, width, frame.bottom + 1,
                paint);
        canvas.drawRect(0, frame.bottom + 1, width, height, paint);


        if (resultBitmap != null) {
            // Draw the opaque result bitmap over the scanning rectangle
            paint.setAlpha(CURRENT_POINT_OPACITY);
            canvas.drawBitmap(resultBitmap, null, frame, paint);
        } else {

            // Draw a red "laser scanner" line through the middle to show
            // decoding is active
            paint.setColor(laserColor);
            paint.setAlpha(SCANNER_ALPHA[scannerAlpha]);
            scannerAlpha = (scannerAlpha + 1) % SCANNER_ALPHA.length;
            int middle = frame.height() / 2 + frame.top;
            canvas.drawRect(frame.left + 2, middle - 1, frame.right - 1,
                    middle + 2, paint);



            float scaleX = frame.width() / (float) previewFrame.width();
            float scaleY = frame.height() / (float) previewFrame.height();

            List<ResultPoint> currentPossible = possibleResultPoints;
            List<ResultPoint> currentLast = lastPossibleResultPoints;
            int frameLeft = frame.left;
            int frameTop = frame.top;
            if (currentPossible.isEmpty()) {
                lastPossibleResultPoints = null;
            } else {
                possibleResultPoints = new ArrayList<ResultPoint>(5);
                lastPossibleResultPoints = currentPossible;
                paint.setAlpha(CURRENT_POINT_OPACITY);
                paint.setColor(resultPointColor);
                synchronized (currentPossible) {
                    for (ResultPoint point : currentPossible) {
                        canvas.drawCircle(frameLeft
                                + (int) (point.getX() * scaleX), frameTop
                                + (int) (point.getY() * scaleY), POINT_SIZE,
                                paint);
                    }
                }
            }
            if (currentLast != null) {
                paint.setAlpha(CURRENT_POINT_OPACITY / 2);
                paint.setColor(resultPointColor);
                synchronized (currentLast) {
                    float radius = POINT_SIZE / 2.0f;
                    for (ResultPoint point : currentLast) {
                        canvas.drawCircle(frameLeft
                                + (int) (point.getX() * scaleX), frameTop
                                + (int) (point.getY() * scaleY), radius, paint);
                    }
                }
            }

            // Request another update at the animation interval, but only
            // repaint the laser line,
            // not the entire viewfinder mask.
            postInvalidateDelayed(ANIMATION_DELAY, frame.left - POINT_SIZE,
                    frame.top - POINT_SIZE, frame.right + POINT_SIZE,
                    frame.bottom + POINT_SIZE);
        }




    }

Answer 1

我猜你正在使用相机。

如果您关闭应用，app / mainActivity的生命周期将从头开始重复（如果您没有后台服务）。

如果你没有在onPause（）或onStop（）或OnDestroy（）等中正确释放相机资源，那么新执行可以拥有前一个的唯一记忆......

你打电话给

之类的东西吗？

   if(camera!=null){
        camera.stopPreview();
        camera.setPreviewCallback(null);
        camera.release();
        camera = null;
    }

在持有相机的活动的OnDestroy（）方法中或者在surfaceDestroyed（）中使用SurfaceView？

onResume时Android Canvas onDraw问题

1 个答案: