setButtonDrawable()的兼容问题

API16实现

    /**     * Set the background to a given Drawable, identified by its resource id.     *     * @param resid the resource id of the drawable to use as the background      */    public void setButtonDrawable(int resid) {        if (resid != 0 && resid == mButtonResource) {            return;        }        mButtonResource = resid;        Drawable d = null;        if (mButtonResource != 0) {            d = getResources().getDrawable(mButtonResource);        }        setButtonDrawable(d);    }    /**     * Set the background to a given Drawable     *     * @param d The Drawable to use as the background     */    public void setButtonDrawable(Drawable d) {        if (d != null) {            if (mButtonDrawable != null) {                mButtonDrawable.setCallback(null);                unscheduleDrawable(mButtonDrawable);            }            d.setCallback(this);            d.setState(getDrawableState());            d.setVisible(getVisibility() == VISIBLE, false);            mButtonDrawable = d;            mButtonDrawable.setState(null);            setMinHeight(mButtonDrawable.getIntrinsicHeight());        }        refreshDrawableState();    }

API23实现

    /**     * Sets a drawable as the compound button image given its resource     * identifier.     *     * @param resId the resource identifier of the drawable     * @attr ref android.R.styleable#CompoundButton_button     */    public void setButtonDrawable(@DrawableRes int resId) {        final Drawable d;        if (resId != 0) {            d = getContext().getDrawable(resId);        } else {            d = null;        }        setButtonDrawable(d);    }    /**     * Sets a drawable as the compound button image.     *     * @param drawable the drawable to set     * @attr ref android.R.styleable#CompoundButton_button     */    @Nullable    public void setButtonDrawable(@Nullable Drawable drawable) {        if (mButtonDrawable != drawable) {            if (mButtonDrawable != null) {                mButtonDrawable.setCallback(null);                unscheduleDrawable(mButtonDrawable);            }            mButtonDrawable = drawable;            if (drawable != null) {                drawable.setCallback(this);                drawable.setLayoutDirection(getLayoutDirection());                if (drawable.isStateful()) {                    drawable.setState(getDrawableState());                }                drawable.setVisible(getVisibility() == VISIBLE, false);                setMinHeight(drawable.getIntrinsicHeight());                applyButtonTint();            }        }    }

结论

RadioButton和CheckBox都是Android app中常用的Widget，它们派生于CompoundButton，允许使用者自行设置背景和按钮的样式，不过，有时我们仅希望简单的设置一个有状态的背景，并隐藏其默认样式。可是，当我们调用setButtonDrawable(null)或setButtonDrawable(0)时，却发现完全没有效果。原来，CompoundButton的setButtonDrawable的代码实现中屏蔽了null或resid为0的Drawable，迫使我们必须传入有效的Drawable对象。

这时候，透明颜色就可以派上用场了：

button.setButtonDrawable(new ColorDrawable(Color.TRANSPARENT));

参考

• 隐藏RadioButton, CheckBox图片 setButtonDrawable（http://blog.csdn.net/changemyself/article/details/44809411）