[Android开发]Android Seekbar竖直

视频播放器页面音量控制Seekbar实现竖直的效果。竖直只是将Seekbar转了90度或-90度，我们可以把画布转一个角度，然后交给系统去画，
具体的做法就是重写ondraw()调整画布，然后调用super.onDraw()。

• 向上的Seekbar

    protected void onDraw(Canvas c) {
c.rotate(-90);
c.translate(-height,0);//height是你的verticalseekbar的高
super.onDraw(c);
}

• 向下的seekbar则应该是：

    protected void onDraw(Canvas c) {
c.rotate(90);
c.translate(0,-width);//width是你的verticalseekbar的宽
super.onDraw(c);
}

• 示例代码

    public class VerticalSeekBar extends SeekBar {
public VerticalSeekBar(Context context) {
super(context);
}
public VerticalSeekBar(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
}
public VerticalSeekBar(Context context, AttributeSet attrs) {
super(context, attrs);
}
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(h, w, oldh, oldw);
}
@Override
protected synchronized void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(heightMeasureSpec, widthMeasureSpec);
setMeasuredDimension(getMeasuredHeight(), getMeasuredWidth());
}
protected void onDraw(Canvas c) {
c.rotate(-90);
c.translate(-getHeight(), 0);
super.onDraw(c);
}
@Override
public synchronized void setProgress(int progress) {
super.setProgress(progress);
onSizeChanged(getWidth(), getHeight(), 0, 0);
}
@Override
public boolean onTouchEvent(MotionEvent event) {
if (!isEnabled()) {
return false;
}
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
case MotionEvent.ACTION_MOVE:
case MotionEvent.ACTION_UP:
setProgress((int) ((int) getMax()- (getMax() * event.getY() / getHeight())));
break;
default:
return super.onTouchEvent(event);
}
return true;
}
}