我正在尝试创建一个透明蒙版。我创建了一个可以扩展的滑动屏幕ViewGroup
。在构造函数中我添加:
LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(LayoutParams.MATCH_PARENT,LayoutParams.MATCH_PARENT);
LinearLayout roadMap = new LinearLayout(context);
roadMap.setLayoutParams(params);
this.addView(roadMap);
然后我覆盖该onDispatchDraw()
方法:
@Override
protected void dispatchDraw(Canvas canvas) {
super.dispatchDraw(canvas);
Log.d("touchy touch", "dispatch draw called");
canvas.drawColor(getResources().getColor(R.color.LIGHT_BLUE));
/* recreate the blue rectangle on the canvas */
path = new Path();
path.moveTo(0.0f, 0.0f); // Top Left
path.lineTo(0.0f, 800.0f); // Bottom Left
path.lineTo(0.0f, 800.0f ); // Bottom Right
path.lineTo(this.x, 0.0f); // Top Right
path.close();
canvas.drawPath(path,paint);
}
结果是我有一个透明蒙版,它等于创建的路径。这不是问题。不幸的是,路线图从不显示。我试图覆盖:
@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
int count = this.getChildCount();
Log.d("children please", "count: "+count);
for (int i = 0; i < count; i++) {
View child = this.getChildAt(i);
child.layout(0, 0, child.getMeasuredWidth(), child.getMeasuredHeight());
child.invalidate();
child.bringToFront();
}
}
然而,我试图附加的线性布局仍然没有出现。