android中checkbox的padding引发的问题

自定义checkbox中的勾选框图标，这次因为想偷懒，图标弄的大了些，然后一系列的问题就都引出来了。

1、图标比checkbox的layout_height高，看不见了。

很吐血吧，CompoundButton中的源码可以看到下面代码

protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);

    final Drawable buttonDrawable = mButtonDrawable;
    if (buttonDrawable != null) {
        final int verticalGravity = getGravity() & Gravity.VERTICAL_GRAVITY_MASK;
        final int height = buttonDrawable.getIntrinsicHeight();//可以看到是根据图片的原始高度对图片进行绘制的，,danielinbiti

        int y = 0;

        switch (verticalGravity) {
            case Gravity.BOTTOM:
                y = getHeight() - height;
                break;
            case Gravity.CENTER_VERTICAL:
                y = (getHeight() - height) / 2;
                break;
        }

        buttonDrawable.setBounds(0, y, buttonDrawable.getIntrinsicWidth(), y + height);
        buttonDrawable.draw(canvas);
    }
}

第一种方法：把原始图片缩小，这就就是制作图片了

第二种方法：重写onDraw方法

@Override
    protected void onDraw(Canvas canvas) {
        setButtonDrawable(parentds);//danielinbiti,<span style="font-family: Arial, Helvetica, sans-serif;">parentds是</span><span style="font-family: Arial, Helvetica, sans-serif;">occupyPosDrawable方法返回的。</span><span style="font-family: Arial, Helvetica, sans-serif;">
</span>        super.onDraw(canvas);
        setButtonDrawable(ds);//真正要显示的图片
        final Drawable buttonDrawable = ds;
        if (buttonDrawable != null) {
            final int verticalGravity = getGravity() & Gravity.VERTICAL_GRAVITY_MASK;
            final int drawableHeight = buttonDrawable.getIntrinsicHeight()>selfHeight
            		?selfHeight:buttonDrawable.getIntrinsicHeight();
            final int drawableWidth = buttonDrawable.getIntrinsicWidth()>selfHeight
            		?selfHeight:buttonDrawable.getIntrinsicWidth();
            //<span style="font-family: Arial, Helvetica, sans-serif;">selfHeight为要定义的图片高度</span>
            int top = 0;
            switch (verticalGravity) {
                case Gravity.BOTTOM:
                    top = getHeight() - drawableHeight;
                    break;
                case Gravity.CENTER_VERTICAL:
                    top = (getHeight() - drawableHeight) / 2;
                    break;
            }
            
            int left = 0;
            int right = left+drawableWidth;
            int bottom = top+drawableHeight;
        	
            buttonDrawable.setBounds(left, top, right, bottom);
            buttonDrawable.draw(canvas);
        }
    }
    // drawable 转换成bitmap
    private Drawable occupyPosDrawable(int height){//
    	Picture p=new Picture();
    	Canvas c=p.beginRecording(height,height);
    	p.endRecording();

    	PictureDrawable pd=new PictureDrawable(p);
    	
    	return pd;
    }

这真的是花了不少时间，结果发现4.1.2版本中CompoundButton没有getCompoundPaddingLeft，这不坑人嘛。两个版本的计算方式不一样，4.2.2版本绘制文字时，会把图片的宽度和paddingLeft的宽度加上，而4.1.2版本只计算设置的paddingLeft，从这里看也是4.2.2版本人性化一些。

于是又查了一下前后版本，发现4.1.2版本是分界线，后续版本CompoundButton都有getCompoundPaddingLeft方法。于是又重写了getCompoundPaddingLeft方法，根据版本判断

@Override
    public int getCompoundPaddingLeft() {
        int padding = super.getCompoundPaddingLeft();
        if(getAndroidSDKVersion()<=16){//4.1.2
	        if (!isLayoutRtl()) {
	            padding = selfHeight + padding;
	        }
        }
        return padding;
    }