Android 自定义View修炼-Android中常见的热门标签的流式布局的实现
一、概述：
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（源码下载在下面最后给出哈）
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<List<View>> mAllChildViews = new ArrayList<>(); //每一行的高度 private List<Integer> 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) child.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); } @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<View> lineViews = new ArrayList<View>(); 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：
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:id="@+id/container" android:layout_width="match_parent" android:layout_height="match_parent" > <com.czm.flowlayout.XCFlowLayout android:id="@+id/flowlayout" android:layout_width="match_parent" android:layout_height="match_parent" > </com.czm.flowlayout.XCFlowLayout> </RelativeLayout>
TextView的样式文件：
<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android" >
<solid android:color="#666666" />
<corners android:radius="10dp" />
<padding
android:left="5dp"
android:right="5dp"
android:top="5dp"
android:bottom="5dp"
/>
</shape>
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); } } }
四、源码下载
最后给出源码的下载：http://www.demodashi.com/demo/14686.html
感谢真题园网提供支持：http://www.zhentiyuan.com
