ShapeDrawable bg = new ShapeDrawable();    //default Ctor
ShapeDrawable hl = new ShapeDrawable();
hl.getPaint().setColor(color1);
bg.getPaint().setColor(color2);

StateListDrawable s1 = new StateListDrawable();
s1.addState(new int[]{android.R.attr.state_pressed},hl);
s1.addState(new int[]{},bg);

但是这在Android 4.2中不再起作用了,抛出了nullpointerexception：

java.lang.NullPointerException
at android.graphics.drawable.ShapeDrawable.mutate(ShapeDrawable.java:387)
at android.graphics.drawable.DrawableContainer.selectDrawable(DrawableContainer.java:315)
at android.graphics.drawable.StateListDrawable.onStateChange(StateListDrawable.java:106)
at android.graphics.drawable.StateListDrawable.addState(StateListDrawable.java:89)

我通过更改ShapeDrawable的构造函数来修复此问题：

ShapeDrawable bg = new ShapeDrawable(new RectShape());
ShapeDrawable hl = new ShapeDrawable(new RectShape());

现在这很好用,但我想知道为什么这对默认构造函数不起作用=)

感谢您的时间 ：)