在Android 4.2中的StateListDrawable中使用默认的ShapeDrawable

Question

任何人都使用了新的问题,ShapeDrawable()在StateListDrawable在Android 4.2？我曾经这样做过:

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);

但这在Android 4.2中不再起作用,抛出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)

我通过更改我的构造函数来修复问题ShapeDrawable:

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 :)

Answer 1

DrawableContainer.selectDrawable()Android 4.2中的实现已经改变,ShapeDrawable必须使用带有args的构造.

如果使用默认的构造函数,调用的时候mutate() mShape是null,这样mShape.clone()将抛出CloneNotSupportedException并返回null.所以你得到一个NullPointerException.