Question

我一直在尝试从缩放后的画布上获取鼠标坐标。 canvas.scale（scale，scale）给我正确的坐标，但是如果我使用canvas.scale（scale，scale，ivotX，ivotY），则坐标是错误的。

//onDraw
canvas.scale(scaleFactor, scaleFactor); //default pivot x & y = 0, 0
//canvas.scale(scaleFactor, scaleFactor, pivotX, pivotY);

private float pixelWidth = 480;
private float pixelHeight = 320; 

//onTouchEvent
touchX = (int) event.getX() * pixelWidth / getWidth();
touchX = (int) event.getY() * pixelHeight / getHeight();

worldX = touchX / scaleFactor;
worldY = touchY / scaleFactor;

我需要怎么做才能从canvas.scale获取具有除默认0、0以外的其他枢轴的正确坐标？我也阅读并尝试过有关矩阵的方法，但是没有运气。

Answer 1

使用矩阵和https://stackoverflow.com/a/20011005/7334711

中的代码解决了该问题

Matrix matrix = new Matrix();

public void render(Canvas canvas) {
    canvas.save();

    matrix.setScale(mScaleFactor, mScaleFactor, pivotX, pivotY);
    canvas.setMatrix(matrix);
...

float[] mv = new float[9];

@Override
public boolean onTouchEvent(MotionEvent event) {

    // Get the values from the matrix into the float array
    matrix.getValues(mv);

    float touchX = (event.getX()*(1/mv[4]) - (mv[2]/mv[4]));
    float touchY = (event.getY()*(1/mv[4]) - (mv[5]/mv[4]));
...

带枢轴，鼠标坐标的canvas.scale

1 个答案: