如何旋转castom seekbar？

Question

GitHub有1300颗恒星的sample如何自定义seekbar，但是没有办法将它从水平旋转到垂直...

当我尝试添加

时

android:rotation="-90"

这是疯狂的旋转，但它仍然需要一个像水平seekbar的空间。

下一步我尝试了seekbar：

public class VerticalDiscreteSeekBar extends DiscreteSeekBar {
public VerticalDiscreteSeekBar(Context context) {
    super(context);
}

public VerticalDiscreteSeekBar(Context context, AttributeSet attrs) {
    super(context, attrs);
}

public VerticalDiscreteSeekBar(Context context, AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
}

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 boolean onTouchEvent(MotionEvent event) {
    if (!isEnabled()) {
        return false;
    }

    switch (event.getAction()) {
        case MotionEvent.ACTION_DOWN:
        case MotionEvent.ACTION_MOVE:
        case MotionEvent.ACTION_UP:
            setProgress(getMax() - (int) (getMax() * event.getY() / getHeight()));
            onSizeChanged(getWidth(), getHeight(), 0, 0);

            break;

        case MotionEvent.ACTION_CANCEL:
            break;
    }
    return true;
}
}

XML

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:orientation="vertical"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".tools.TestDeleteIt">

<com.example.android.camera2basic.tools.VerticalDiscreteSeekBar
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:dsb_thumbColor="@color/color_white"
    app:dsb_indicatorColor="@color/color_white"
    app:dsb_indicatorFormatter="%03d"
      app:dsb_indicatorTextAppearance="@style/CustomFloaterTextAppearance"
    app:dsb_max="14"
    app:dsb_min="-14"
    app:dsb_progressColor="@color/ntz_color_yellow"
    app:dsb_rippleColor="@color/ntz_color_yellow"
    app:dsb_scrubberHeight="10dp"
    app:dsb_thumbSize="25dp"
    app:dsb_trackColor="@color/ntz_color_yellow"
    app:dsb_trackHeight="10dip"/>
</LinearLayout>

最终看起来如此（它只显示形状，但没有真实视图）

我做错了什么？我怎么能让它运作起来？