一、概述：在日常的app使用中，我們會在android 的app中看見 熱門标簽等自動換行的流式布局，今天，我們就來看看如何
自定義一個類似熱門标簽那樣的流式布局吧(×××在下面最後給出)
類似的自定義布局。下面我們就來詳細介紹流式布局的應用特點以及用的的技術點：
1.流式布局的特點以及應用場景 特點：當上面一行的空間不夠容納新的TextView時候， 才開辟下一行的空間
原理圖：
場景：主要用于關鍵詞搜尋或者熱門标簽等場景2.自定義ViewGroup,重點重寫下面兩個方法
1、onMeasure:測量子view的寬高，設定自己的寬和高
2、onLayout:設定子view的位置
onMeasure:根據子view的布局檔案中屬性，來為子view設定測量模式和測量值 測量=測量模式+測量值；
測量模式有3種： EXACTLY：表示設定了精确的值，一般當childView設定其寬、高為精确值、match_parent時，ViewGroup會将其設定為EXACTLY； AT_MOST：表示子布局被限制在一個最大值内，一般當childView設定其寬、高為wrap_content時，ViewGroup會将其設定為AT_MOST； UNSPECIFIED：表示子布局想要多大就多大，一般出現在AadapterView的item的heightMode中、ScrollView的childView的heightMode中；此種模式比較少見。3.LayoutParams ViewGroup LayoutParams :每個 ViewGroup 對應一個 LayoutParams; 即 ViewGroup -> LayoutParams getLayoutParams 不知道轉為哪個對應的LayoutParams ,其實很簡單，就是如下： 子View.getLayoutParams 得到的LayoutParams對應的就是 子View所在的父控件的LayoutParams; 例如，LinearLayout 裡面的子view.getLayoutParams ->LinearLayout.LayoutParams 是以 咱們的FlowLayout 也需要一個LayoutParams，由于上面的效果圖是子View的 margin， 是以應該使用MarginLayoutParams。即FlowLayout->MarginLayoutParams
4.最後來看看實作的最終效果圖：
二、熱門标簽的流式布局的實作：
1. 自定義熱門标簽的ViewGroup實作
根據上面的技術分析，自定義類繼承于ViewGroup，并重寫 onMeasure和onLayout等方法。具體實作代碼如下：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;
public class XCFlowLayout extends ViewGroup{
//存儲所有子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
//父控件傳進來的寬度和高度以及對應的測量模式
int sizeWidth = MeasureSpec.getSize(widthMeasureSpec);
int modeWidth = MeasureSpec.getMode(widthMeasureSpec);
int sizeHeight = MeasureSpec.getSize(heightMeasureSpec);
int modeHeight = MeasureSpec.getMode(heightMeasureSpec);
//如果目前ViewGroup的寬高為wrap_content的情況
int width = 0;//自己測量的 寬度
int height = 0;//自己測量的高度
//記錄每一行的寬度和高度
int lineWidth = 0;
int lineHeight = 0;
//擷取子view的個數
int childCount = getChildCount();
for(int i = 0;i < childCount; i ++){
View child = getChildAt(i);
//測量子View的寬和高
measureChild(child, widthMeasureSpec, heightMeasureSpec);
//得到LayoutParams
MarginLayoutParams lp = (MarginLayoutParams) getLayoutParams();
//子View占據的寬度
int childWidth = child.getMeasuredWidth() + lp.leftMargin + lp.rightMargin;
//子View占據的高度
int childHeight = child.getMeasuredHeight() + lp.topMargin + lp.bottomMargin;
//換行時候
if(lineWidth + childWidth > sizeWidth){
//對比得到最大的寬度
width = Math.max(width, lineWidth);
//重置lineWidth
lineWidth = childWidth;
//記錄行高
height += lineHeight;
lineHeight = childHeight;
}else{//不換行情況
//疊加行寬
lineWidth += childWidth;
//得到最大行高
lineHeight = Math.max(lineHeight, childHeight);
}
//處理最後一個子View的情況
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();
//擷取目前ViewGroup的寬度
int width = getWidth();
int lineWidth = 0;
int lineHeight = 0;
//記錄目前行的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();
//如果需要換行
if(childWidth + lineWidth + lp.leftMargin + lp.rightMargin > width){
//記錄LineHeight
mLineHeight.add(lineHeight);
//記錄目前行的Views
mAllChildViews.add(lineViews);
//重置行的寬高
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);
}
//處理最後一行
mLineHeight.add(lineHeight);
mAllChildViews.add(lineViews);
//設定子View的位置
int left = 0;
int top = 0;
//擷取行數
int lineCount = mAllChildViews.size();
for(int i = 0; i < lineCount; i ++){
//目前行的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);
//判斷是否顯示
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();
//進行子View進行布局
child.layout(cLeft, cTop, cRight, cBottom);
left += child.getMeasuredWidth() + lp.leftMargin + lp.rightMargin;
}
left = 0;
top += lineHeight;
}
}
@Override
public LayoutParams generateLayoutParams(AttributeSet attrs) {
// TODO Auto-generated method stub
return new MarginLayoutParams(getContext(), attrs);
}
}
2.相關的布局檔案：
引用自定義控件：
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的樣式檔案：<?xml version="1.0" encoding="utf-8"?>
android:left="5dp"
android:right="5dp"
android:top="5dp"
android:bottom="5dp"
/>
三、使用該自定義布局控件類
最後，如何使用該自定義的熱門标簽控件類呢？很簡單，請看下面執行個體代碼：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;
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、×××
此×××完之後，往往有個要點我們容易忽略，那就是源碼的安全性問題，此處可點選移動應用安全智能服務提供商愛加密的Android加密，源碼保護！