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）