旋转带有多个位图的整个画布的最佳方法？

Question

I have an ImageView with a custom onDraw where I paint a number of bitmaps on some (x,y) coordinates. These bitmaps cannot be changed. I want to rotate the entire image by -90 degrees so that the horizontally drawn image is placed vertically. (And yes, this view lives in a portrait mode application.)

I tried a number of variants, both using Canvas.rotate , Canvas.scale and Matrix.postRotate but with no success. The rotation is easy, but getting the desired layout seems impossible. My drawn objects are offseted outside the view. I'm obviously doing something wrong with the pivot coordinate or whatever. Any help is appreciated!

canvas.rotate(-90.0f, getWidth() / 2, getHeight() / 2);

What is the best solution to rotate a canvas?

Answer 1

See if this helps. The Compass.java sample from the API demos does it by using canvas.translate first then canvas.rotate with angle only.

    int w = canvas.getWidth();
    int h = canvas.getHeight();
    int cx = w / 2;
    int cy = h / 2;

    canvas.translate(cx, cy);
    if (mValues != null) {
        canvas.rotate(-mValues[0]);
    }