所以我自己能够回答这个问题......我使用路径来创建drawables，然后将它们拼接在一起以创建平行四边形。

public Drawable createThumbDrawable(boolean checked){

Path path = new Path();

path.moveTo(0, 0);

path.lineTo(1, 0);

path.lineTo(1, 1);

path.lineTo(0, 1);

path.close();

PathShape shape = new PathShape(path, 1, 1);

ShapeDrawable drawable = new ShapeDrawable(shape);

if (checked){

drawable.getPaint().setColor(Color.CYAN);

}

else

{

drawable.getPaint().setColor(Color.BLACK);

}

mThumbLeftDrawable = createLeftThumbDrawable(checked);

mThumbRightDrawable = createRightThumbDrawable(checked);

return drawable;

}

public Drawable createLeftThumbDrawable(boolean checked){

Path path = new Path();

path.moveTo(0, 25);

path.lineTo(25, 0);

path.lineTo(25, 25);

path.close();

PathShape shape = new PathShape(path, 25, 25);

ShapeDrawable drawable = new ShapeDrawable(shape);

if (checked){

drawable.getPaint().setColor(Color.CYAN);

}

else

{

drawable.getPaint().setColor(Color.BLACK);

}

return drawable;

}

public Drawable createRightThumbDrawable(boolean checked){

Path path = new Path();

path.moveTo(0,0);

path.lineTo(25, 0);

path.lineTo(0, 25);

path.close();

PathShape shape = new PathShape(path, 25, 25);

ShapeDrawable drawable = new ShapeDrawable(shape);

if (checked){

drawable.getPaint().setColor(Color.CYAN);

}

else

{

drawable.getPaint().setColor(Color.BLACK);

}

return drawable;

}

public void setChecked(boolean checked) {

//Log.d(TAG, "setChecked("+checked+")");

boolean lc = checked;

if (!mTextOnThumb) {

lc = !checked;

}

if (checked){

mThumbDrawable = createThumbDrawable(checked);//this.getContext().getResources().getDrawable(R.drawable.slide_off);

}

else {

mThumbDrawable = createThumbDrawable(checked);//this.getContext().getResources().getDrawable(R.drawable.slide);

}

super.setChecked(checked);

mThumbPosition = lc ? getThumbScrollRange() : 0;

invalidate();

}