Android:SeekBar 小部件中的自定义 Drawable 正在绘制别名图像

I'm guessing one idea would be to just overlay my on_off image onto the ShapeDrawable and use that as the background (and "@android:color/transparent" for progressDrawable), but I'm not too familiar with how to do that...

新活动的基本代码

    @Override
    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        seek = (SeekBar)findViewById(R.id.seek);
        seek.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
            public void onProgressChanged(SeekBar seekBar, int progress, boolean fromTouch) {
            }
            public void onStartTrackingTouch(SeekBar seekBar) { 
            }
            public void onStopTrackingTouch(SeekBar seekBar) {
                if (seek.getProgress() < seek.getMax() / 2.0)
                    seek.setProgress(0);
                else
                    seek.setProgress(seek.getMax());
            }
        });
    }

定义 SeekBar 的 main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:background="#FFFFFF">
    <SeekBar android:id="@+id/seek"
                android:layout_alignParentTop="true" 
                android:layout_centerHorizontal="true"
                android:layout_height="wrap_content" android:layout_width="200dip" 
                android:background="@drawable/background"
                android:padding="4dip" 
                android:drawingCacheQuality="high" 
                android:progressDrawable="@drawable/slider_on_off"  
                android:progress="99" android:max="99" 
                android:maxHeight="100dip"
                android:thumb="@drawable/slider_box"
                android:thumbOffset="0dip"
                />
</RelativeLayout>

<?xml version="1.0" encoding="utf-8"?>
<shape
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle" 
    android:useLevel="false" >
    <corners 
        android:radius="4dip" />
    <solid
        android:color="#FF282828" />
</shape>