流式布局，标签式布局

一、概述：

资源下载 ：http://download.csdn.net/detail/husuxing/9923179
在日常的app使用中，我们会在Android 的app中看见 热门标签等自动换行的流式布局，今天，我们就来看看如何

自定义一个类似热门标签那样的流式布局吧

类似的自定义布局。下面我们就来详细介绍流式布局的应用特点以及用的的技术点：

1.流式布局的特点以及应用场景
    特点：当上面一行的空间不够容纳新的TextView时候，
    才开辟下一行的空间

　　原理图：

　　

    场景：主要用于关键词搜索或者热门标签等场景
2.自定义ViewGroup,重点重写下面两个方法

    1、onMeasure:测量子view的宽高，设置自己的宽和高

    2、onLayout:设置子view的位置

    onMeasure:根据子view的布局文件中属性，来为子view设置测量模式和测量值
    测量=测量模式+测量值；

    测量模式有3种：
    EXACTLY：表示设置了精确的值，一般当childView设置其宽、高为精确值、match_parent时，ViewGroup会将其设置为EXACTLY；
    AT_MOST：表示子布局被限制在一个最大值内，一般当childView设置其宽、高为wrap_content时，ViewGroup会将其设置为AT_MOST；
    UNSPECIFIED：表示子布局想要多大就多大，一般出现在AadapterView的item的heightMode中、ScrollView的childView的heightMode中；此种模式比较少见。
3.LayoutParams
    ViewGroup LayoutParams :每个 ViewGroup 对应一个 LayoutParams; 即 ViewGroup -> LayoutParams
    getLayoutParams 不知道转为哪个对应的LayoutParams ,其实很简单，就是如下：
    子View.getLayoutParams 得到的LayoutParams对应的就是 子View所在的父控件的LayoutParams;
    例如，LinearLayout 里面的子view.getLayoutParams ->LinearLayout.LayoutParams
    所以 咱们的FlowLayout 也需要一个LayoutParams，由于上面的效果图是子View的 margin，
    所以应该使用MarginLayoutParams。即FlowLayout->MarginLayoutParams

4.最后来看看实现的最终效果图：

二、热门标签的流式布局的实现：

1. 自定义热门标签的ViewGroup实现

　　根据上面的技术分析，自定义类继承于ViewGroup，并重写 onMeasure和onLayout等方法。具体实现代码如下：

 package com.czm.flowlayout;

 import java.util.ArrayList;
 import java.util.List;

 import android.content.Context;
 import android.util.AttributeSet;
 import android.view.View;
 import android.view.ViewGroup;
 /**
  *
  * @author caizhiming
  * @created on 2015-4-13
  */
 public class XCFlowLayout extends ViewGroup{

     //存储所有子View
     private List> mAllChildViews = new ArrayList<>();
     //每一行的高度
     private List mLineHeight = new ArrayList<>();

     public XCFlowLayout(Context context) {
         this(context, null);
         // TODO Auto-generated constructor stub
     }
     public XCFlowLayout(Context context, AttributeSet attrs) {
         this(context, attrs, 0);
         // TODO Auto-generated constructor stub
     }
     public XCFlowLayout(Context context, AttributeSet attrs, int defStyle) {
         super(context, attrs, defStyle);
         // TODO Auto-generated constructor stub
     }
     @Override
     protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
         // TODO Auto-generated method stub

         //父控件传进来的宽度和高度以及对应的测量模式
         int sizeWidth = MeasureSpec.getSize(widthMeasureSpec);
         int modeWidth = MeasureSpec.getMode(widthMeasureSpec);
         int sizeHeight = MeasureSpec.getSize(heightMeasureSpec);
         int modeHeight = MeasureSpec.getMode(heightMeasureSpec);

         //如果当前ViewGroup的宽高为wrap_content的情况
         int width = 0;//自己测量的 宽度
         int height = 0;//自己测量的高度
         //记录每一行的宽度和高度
         int lineWidth = 0;
         int lineHeight = 0;

         //获取子view的个数
         int childCount = getChildCount();
         for(int i = 0;i < childCount; i ++){
             View child = getChildAt(i);
             //测量子View的宽和高
             measureChild(child, widthMeasureSpec, heightMeasureSpec);
             //得到LayoutParams
             MarginLayoutParams lp = (MarginLayoutParams) getLayoutParams();
             //子View占据的宽度
             int childWidth = child.getMeasuredWidth() + lp.leftMargin + lp.rightMargin;
             //子View占据的高度
             int childHeight = child.getMeasuredHeight() + lp.topMargin + lp.bottomMargin;
             //换行时候
             if(lineWidth + childWidth > sizeWidth){
                 //对比得到最大的宽度
                 width = Math.max(width, lineWidth);
                 //重置lineWidth
                 lineWidth = childWidth;
                 //记录行高
                 height += lineHeight;
                 lineHeight = childHeight;
             }else{//不换行情况
                 //叠加行宽
                 lineWidth += childWidth;
                 //得到最大行高
                 lineHeight = Math.max(lineHeight, childHeight);
             }
             //处理最后一个子View的情况
             if(i == childCount -1){
                 width = Math.max(width, lineWidth);
                 height += lineHeight;
             }
         }
         //wrap_content
         setMeasuredDimension(modeWidth == MeasureSpec.EXACTLY ? sizeWidth : width,
                 modeHeight == MeasureSpec.EXACTLY ? sizeHeight : height);
         super.onMeasure(widthMeasureSpec, heightMeasureSpec);
     }

     @Override
     protected void onLayout(boolean changed, int l, int t, int r, int b) {
         // TODO Auto-generated method stub
         mAllChildViews.clear();
         mLineHeight.clear();
         //获取当前ViewGroup的宽度
         int width = getWidth();

         int lineWidth = 0;
         int lineHeight = 0;
         //记录当前行的view
         List lineViews = new ArrayList();
         int childCount = getChildCount();
         for(int i = 0;i < childCount; i ++){
             View child = getChildAt(i);
             MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams();
             int childWidth = child.getMeasuredWidth();
             int childHeight = child.getMeasuredHeight();

             //如果需要换行
             if(childWidth + lineWidth + lp.leftMargin + lp.rightMargin > width){
                 //记录LineHeight
                 mLineHeight.add(lineHeight);
                 //记录当前行的Views
                 mAllChildViews.add(lineViews);
                 //重置行的宽高
                 lineWidth = 0;
                 lineHeight = childHeight + lp.topMargin + lp.bottomMargin;
                 //重置view的集合
                 lineViews = new ArrayList();
             }
             lineWidth += childWidth + lp.leftMargin + lp.rightMargin;
             lineHeight = Math.max(lineHeight, childHeight + lp.topMargin + lp.bottomMargin);
             lineViews.add(child);
         }
         //处理最后一行
         mLineHeight.add(lineHeight);
         mAllChildViews.add(lineViews);

         //设置子View的位置
         int left = 0;
         int top = 0;
         //获取行数
         int lineCount = mAllChildViews.size();
         for(int i = 0; i < lineCount; i ++){
             //当前行的views和高度
             lineViews = mAllChildViews.get(i);
             lineHeight = mLineHeight.get(i);
             for(int j = 0; j < lineViews.size(); j ++){
                 View child = lineViews.get(j);
                 //判断是否显示
                 if(child.getVisibility() == View.GONE){
                     continue;
                 }
                 MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams();
                 int cLeft = left + lp.leftMargin;
                 int cTop = top + lp.topMargin;
                 int cRight = cLeft + child.getMeasuredWidth();
                 int cBottom = cTop + child.getMeasuredHeight();
                 //进行子View进行布局
                 child.layout(cLeft, cTop, cRight, cBottom);
                 left += child.getMeasuredWidth() + lp.leftMargin + lp.rightMargin;
             }
             left = 0;
             top += lineHeight;
         }

     }
     /**
      * 与当前ViewGroup对应的LayoutParams
      */
     @Override
     public LayoutParams generateLayoutParams(AttributeSet attrs) {
         // TODO Auto-generated method stub

         return new MarginLayoutParams(getContext(), attrs);
     }
 }

2.相关的布局文件：

引用自定义控件：

     xmlns:tools="http://schemas.android.com/tools"
     android:id="@+id/container"
     android:layout_width="match_parent"
     android:layout_height="match_parent" >


         android:id="@+id/flowlayout"
         android:layout_width="match_parent"
         android:layout_height="match_parent" >

TextView的样式文件：

         android:left="5dp"
         android:right="5dp"
         android:top="5dp"
         android:bottom="5dp"
         />

三、使用该自定义布局控件类

最后，如何使用该自定义的热门标签控件类呢？很简单，请看下面实例代码：

 package com.czm.flowlayout;

 import android.app.Activity;
 import android.graphics.Color;
 import android.os.Bundle;
 import android.view.ViewGroup.LayoutParams;
 import android.view.ViewGroup.MarginLayoutParams;
 import android.widget.TextView;
 /**
  *
  * @author caizhiming
  * @created on 2015-4-13
  */
 public class MainActivity extends Activity {

     private String mNames[] = {
             "welcome","android","TextView",
             "apple","jamy","kobe bryant",
             "jordan","layout","viewgroup",
             "margin","padding","text",
             "name","type","search","logcat"
     };
     private XCFlowLayout mFlowLayout;
     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);

         initChildViews();

     }
     private void initChildViews() {
         // TODO Auto-generated method stub
         mFlowLayout = (XCFlowLayout) findViewById(R.id.flowlayout);
         MarginLayoutParams lp = new MarginLayoutParams(
                 LayoutParams.WRAP_CONTENT,LayoutParams.WRAP_CONTENT);
         lp.leftMargin = 5;
         lp.rightMargin = 5;
         lp.topMargin = 5;
         lp.bottomMargin = 5;
         for(int i = 0; i < mNames.length; i ++){
             TextView view = new TextView(this);
             view.setText(mNames[i]);
             view.setTextColor(Color.WHITE);
             view.setBackgroundDrawable(getResources().getDrawable(R.drawable.textview_bg));
             mFlowLayout.addView(view,lp);
         }
     }

 }