Question

我正在尝试将Pinch缩放到位置。我现在正在研究它一个星期，我无法弄明白。

这是我的问题：

我创建了一个自定义视图，扩展了SurfaceView并实施了ScalingGestureDetector。一切正常，而我尚未缩放我的画布或枢轴点与之前的缩放相同。当枢轴点与前一个缩放点不同时，画布会跳转到不同的x，y位置并缩放到它而不是手指焦点。我不能使用矩阵，因为我绘制文本和rects，而不是位图。

这是我的代码

public class CustomSurfaceView extends SurfaceView implements SurfaceHolder.Callback, ScaleGestureDetector.OnScaleGestureListener {
    private ScaleGestureDetector mScaleDetector;
    private float focusX, focusY;
    private float scale = 1f;

    private void init(Context context) {
        mScaleDetector = new ScaleGestureDetector(context, this);
        getHolder().addCallback(this);

        // other init code
    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        tryDrawing(holder);
    }

    @Override
    public void surfaceChanged(SurfaceHolder holder, int frmt, int w, int h) {
        tryDrawing(holder);
    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {}

    public void tryDrawing() {
        tryDrawing(getHolder());
    }

    private void drawMyStuff(final Canvas canvas) {
        Log.i(TAG, "Drawing...");

        for(Pixel pixel : pixels) {
            drawRect(canvas, pixel);
        }
    }

    public void tryDrawing(SurfaceHolder holder) {
        Log.i(TAG, "Trying to draw...");

        Canvas canvas = holder.lockCanvas();
        if (canvas == null) {
            Log.e(TAG, "Cannot draw onto the canvas as it's null");
        } else {
            canvas.scale(scale, scale, focusX , focusY);
            canvas.drawColor(Color.WHITE);
            drawMyStuff(canvas);

            holder.unlockCanvasAndPost(canvas);
        }
    }

    @Override
    public boolean onScale(ScaleGestureDetector detector) {
        scale *= detector.getScaleFactor();

        // Don't let the object get too small or too large.
        scale = Math.max(1.0f, Math.min(scale, 5.0f));

        tryDrawing();
        return true;

    }

    @Override
    public boolean onScaleBegin(ScaleGestureDetector detector) {
        focusX = detector.getFocusX();
        focusY = detector.getFocusY();
        return true;
    }

    @Override
    public void onScaleEnd(ScaleGestureDetector detector) {
    }
}`

如果有人不明白我的意思，我可以稍后制作一些视频。

谢谢！

Answer 1

在我的一个项目中，我遇到了像您一样的问题。我尝试跳出框框思考，而不是试图给出一个标尺。
我使用了默认的轴（左上角..），但是我将画布平移到了轴上，因此左上角将位于轴的位置。之后，我翻译了位图并将其调整回正确的位置。这样的事情可能会做到：

private void drawMyStuff(final Canvas canvas) {

    Log.i(TAG, "Drawing...");

    for(Pixel pixel : pixels) {
        drawRect(canvas, pixel); // translate your rect with x : -focusX, y: -focusY
    }
}

public void tryDrawing(SurfaceHolder holder) {
    Log.i(TAG, "Trying to draw...");

    Canvas canvas = holder.lockCanvas();
    if (canvas == null) {
        Log.e(TAG, "Cannot draw onto the canvas as it's null");
    } else {
        // Translate the canvas (so the top left corner will be in the wanted position and you can use it as a pivot)
        canvas.translate(focusX , focusY);
        canvas.scale(scale, scale); // Use the default 0,0 pivot
        canvas.drawColor(Color.WHITE);
        drawMyStuff(canvas);

        holder.unlockCanvasAndPost(canvas);
    }
}

希望有帮助。

Android画布用缩放点缩放到缩放

1 个答案: