Android开发之LayoutParams的用法

来源：互联网发布：ubuntu 精简编辑：程序博客网时间：2024/06/06 00:48

LayoutParams继承于Android.View.ViewGroup.LayoutParams.
LayoutParams相当于一个Layout的信息包，它封装了Layout的位置、高、宽等信息。假设在屏幕上一块区域是由一个Layout占领的，如果将一个View添加到一个Layout中，最好告诉Layout用户期望的布局方式，也就是将一个认可的layoutParams传递进去。
可以这样去形容LayoutParams，在象棋的棋盘上，每个棋子都占据一个位置，也就是每个棋子都有一个位置的信息，如这个棋子在4行4列，这里的“4行4列”就是棋子的LayoutParams。

但LayoutParams类也只是简单的描述了宽高，宽和高都可以设置成三种值：
1，一个确定的值；
2，FILL_PARENT，即填满（和父容器一样大小）；
3，WRAP_CONTENT，即包裹住组件就好。
在JAVA中动态构建的布局，常常这样写：

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setLayoutParams(newLayoutParams(LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT));

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上面这一句话其实是子对父的，也就是说，父布局下的子控件要设置这句话。
 
 
因为布局很多，虽然都继承至ViewGroup但是各个布局还是有很大的不同。
 
 
很显然上面这句应该这样写才算准确：

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setLayoutParams(newTableRow.LayoutParams(TableRow.LayoutParams.FILL_PARENT,TableRow.LayoutParams.FILL_PARENT));

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这表示这个子控件的父布局是一个TableRow , 这样的LayoutParams 太多，所以应明确指明。
 
下面分别说下两个常用到布局:
1. FrameLayout下动态设置子控件居中，动态用JAVA代码要这样实现:这表示这个子控件的父布局是一个TableRow , 这样的LayoutParams 太多，所以应明确指明。
下面分别说下两个常用到布局:
1. FrameLayout下动态设置子控件居中，动态用JAVA代码要这样实现:

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FrameLayout.LayoutParams lytp = newFrameLayout.LayoutParams(80,LayoutParams.WRAP_CONTENT);
lytp .gravity = Gravity.CENTER;
btn.setLayoutParams(lytp);

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2. RelativeLayout下动态设置子控件居中：

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RelativeLayout.LayoutParams lp=newRelativeLayout.LayoutParams(LayoutParams.WRAP_CONTENT,LayoutParams.WRAP_CONTENT);
lp.addRule(RelativeLayout.ALIGN_PARENT_RIGHT, RelativeLayout.TRUE); 
lp.addRule(RelativeLayout.ALIGN_PARENT_TOP, RelativeLayout.TRUE); 
btn1.setLayoutParams(lp);

实例：

从网页响应获取Json 对象，并解析

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@SuppressWarnings(unchecked)
        Map<string,object> markJsonMap = (Map<string, object="">) mapJson.get(adlogo);
        if(markJsonMap != null){
            String position = (String) markJsonMap.get(position);
            String markTumbString = (String) markJsonMap.get(thumb);
            String smlscreen = (String) markJsonMap.get(smlscreen);
            String bigscreen = (String) markJsonMap.get(bigscreen);
            HomeActivity.mCornerMark.setPosition(position);
            HomeActivity.mCornerMark.setThumb(markTumbString);
            HomeActivity.mCornerMark.setSmlscreen(smlscreen);
            HomeActivity.mCornerMark.setBigscreen(bigscreen);
            setCornerMark();
        }</string,></string,object>

解析后代码设置角标图片的大小，位置，异步下载图片

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/**
     * 动态设置角标位置
     * */
    privatevoid setCornerMark(){
        if(!HomeActivity.mCornerMark.getThumb().equals() && HomeActivity.mCornerMark.getThumb().length() != 0)
        {
//          WindowManager wm = (WindowManager) mContex
//                  .getSystemService(Context.WINDOW_SERVICE);
//
//          int width = wm.getDefaultDisplay().getWidth();
//          int height = wm.getDefaultDisplay().getHeight();
 
            FrameLayout.LayoutParams reParams = (android.widget.FrameLayout.LayoutParams) HomeActivity.home_surface_viewLyout.getLayoutParams();
            intwidth = reParams.width;
            intheight = reParams.height;
            RelativeLayout.LayoutParams params;
            //width, height * 48 / 128
            //获取控件布局参数
            Configuration config = mContex.getResources().getConfiguration();
            if(config.orientation == Configuration.ORIENTATION_LANDSCAPE)
            {
                String[] paramString = HomeActivity.mCornerMark.getBigscreen().split(,);
                intwhidthString = Integer.parseInt(paramString[0]);
                intheightString = Integer.parseInt(paramString[1]);
                //转dp
                whidthString = DensityUtil.px2dip(mContex,whidthString);
                heightString = DensityUtil.px2dip(mContex,heightString);
                params = newLayoutParams(whidthString,heightString);
            }else{
                String[] paramString = HomeActivity.mCornerMark.getSmlscreen().split(,);
                intwhidthString = Integer.parseInt(paramString[0]);
                intheightString = Integer.parseInt(paramString[1]);
                //转dp
                whidthString = (int) (width*0.005*whidthString);
                heightString = (int) (height*0.005*heightString);
                 
                whidthString = DensityUtil.px2dip(mContex,whidthString);
                heightString = DensityUtil.px2dip(mContex,heightString);
                params = newRelativeLayout.LayoutParams(whidthString,heightString);
            }
 
            //动态指定控件大小,位置
            Log.v(Position, HomeActivity.mCornerMark.getPosition());
            if(HomeActivity.mCornerMark.getPosition().equals(1)){
                params.leftMargin=20;
                params.topMargin=20;
                params.addRule(RelativeLayout.ALIGN_PARENT_LEFT, RelativeLayout.TRUE);
                params.addRule(RelativeLayout.ALIGN_PARENT_TOP, RelativeLayout.TRUE);
            }
            elseif(HomeActivity.mCornerMark.getPosition().equals(2)){
                params.rightMargin=20;
                params.topMargin=20;
                params.addRule(RelativeLayout.ALIGN_PARENT_RIGHT, RelativeLayout.TRUE);
                params.addRule(RelativeLayout.ALIGN_PARENT_TOP, RelativeLayout.TRUE);
            }elseif (HomeActivity.mCornerMark.getPosition().equals(3)) {
                params.leftMargin=20;
                params.bottomMargin=20;
                params.addRule(RelativeLayout.ALIGN_PARENT_LEFT, RelativeLayout.TRUE);
                params.addRule(RelativeLayout.ALIGN_PARENT_BOTTOM, RelativeLayout.TRUE);
            }elseif(HomeActivity.mCornerMark.getPosition().equals(4)){
                params.rightMargin=20;
                params.bottomMargin=20;
                params.addRule(RelativeLayout.ALIGN_PARENT_RIGHT, RelativeLayout.TRUE);
                params.addRule(RelativeLayout.ALIGN_PARENT_BOTTOM, RelativeLayout.TRUE);
            }
 
 
            HomeActivity.img_cornermark.setLayoutParams(params);
 
            DownLoadTask downLoadTask = newDownLoadTask(HomeActivity.img_cornermark);
            downLoadTask.execute(HomeActivity.mCornerMark.getThumb());
 
        }
    }

遇到的问题：

1. 在RelativeLayout里的布局，图片不显示？

RelativeLayout 层次布局是通过xml 文件 Relativelayout 由底层到外层进行布局的，应该在底层布局之上

2.在RelativeLayout里，代码实现位置是用

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<span style="white-space:pre">  </span>params.addRule(RelativeLayout.ALIGN_PARENT_LEFT, RelativeLayout.TRUE);
    params.addRule(RelativeLayout.ALIGN_PARENT_TOP, RelativeLayout.TRUE);

3.不同手机分辨率等比列显示：

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String[] paramString = HomeActivity.mCornerMark.getSmlscreen().split(,);
                intwhidthString = Integer.parseInt(paramString[0]);
                intheightString = Integer.parseInt(paramString[1]);
                //转dp
                whidthString = (int) (width*0.005*whidthString);
                heightString = (int) (height*0.005*heightString);
                 
                whidthString = DensityUtil.px2dip(mContex,whidthString);
                heightString = DensityUtil.px2dip(mContex,heightString);
                params = newRelativeLayout.LayoutParams(whidthString,heightString);

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