java - 在 Canvas 中绘制可绘制不起作用

Question

我想用这段代码在 Canvas 上绘制一个可绘制对象，但它不起作用，我也不知道为什么

getResources().getDrawable(R.drawable.allergist).draw(canvas);

我将自定义 View 的高度和宽度设置为与父级匹配，但整个屏幕都是白色的，屏幕上没有可绘制对象

Answer 1

You need to load your image as bitmap:

 Resources res = getResources();
 Bitmap bitmap = BitmapFactory.decodeResource(res, R.drawable.allergist);

Then make the bitmap mutable and create a canvas over it:

Canvas canvas = new Canvas(bitmap.copy(Bitmap.Config.ARGB_8888, true));

After that you can draw it on canvas.

编辑 1

Set bounds To Drawable.

Drawable d = getResources().getDrawable(R.drawable.allergist);
d.setBounds(left, top, right, bottom);
d.draw(canvas);