android 实现自动换行的流布局

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今天为大家带来一个自定义的ViewGroup自动换行的流布局。原理非常的简单。就是在自定义的ViewGroup的onMeasure中计算每个子View的位置，再在onLayout中画出子View。别的不多说，直接上代码。

 package com.ljh.flowviewgroup;import android.content.Context;import android.os.Build;import android.util.ArrayMap;import android.util.AttributeSet;import android.view.View;import android.view.ViewGroup;import java.util.HashMap;import java.util.Map;import java.util.Objects;/** * Created by liujinhua on 15/10/8. */public class FlowViewGroup extends ViewGroup {    public FlowViewGroup(Context context, AttributeSet attrs, int defStyleAttr) {        super(context, attrs, defStyleAttr);    }    public FlowViewGroup(Context context, AttributeSet attrs) {        this(context, attrs, 0);    }    public FlowViewGroup(Context context) {        this(context, null);    }    @Override    protected LayoutParams generateDefaultLayoutParams() {        return new MarginLayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);    }    private Map<View, ChildViewPosition> map;    @Override    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {        if (map == null) {            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {                map = new ArrayMap<View, ChildViewPosition>();            } else {                map = new HashMap<View, ChildViewPosition>();            }        } else {            map.clear();        }        //计算所有ziView的大小        measureChildren(widthMeasureSpec, heightMeasureSpec);        int sizeWidth = MeasureSpec.getSize(widthMeasureSpec);        int sizeHight = MeasureSpec.getSize(heightMeasureSpec);        int widthMode = MeasureSpec.getMode(widthMeasureSpec);        int hightMode = MeasureSpec.getMode(heightMeasureSpec);        int lineWidth = 0;        int lineHight = 0;        int width = 0;        int hight = 0;        int childCount = getChildCount();        for (int i = 0; i < childCount; i++) {            View childView = getChildAt(i);            MarginLayoutParams lp;            if (childView.getLayoutParams() instanceof MarginLayoutParams) {                lp = (MarginLayoutParams) childView.getLayoutParams();            } else {                lp = new MarginLayoutParams(childView.getLayoutParams());            }            int childWidth = childView.getMeasuredWidth() + lp.leftMargin + lp.rightMargin;            int childHight = childView.getMeasuredHeight() + lp.bottomMargin + lp.topMargin;            //判断是非需要换行            if (lineWidth + childWidth > sizeWidth) {                //需要换行                //计算ViewGroup需要的宽高                width = Math.max(width, lineWidth);                hight += lineHight;                //换行重置当前行高度与宽度                lineHight = childHight;                lineWidth = childWidth;                map.put(childView, new ChildViewPosition(0 + lp.leftMargin, hight + lp.topMargin, childWidth - lp.rightMargin, hight + childHight - lp.bottomMargin));            } else {                //不需要换行                map.put(childView, new ChildViewPosition(lineWidth + lp.leftMargin, hight + lp.topMargin, lineWidth + childWidth - lp.rightMargin, hight + childHight - lp.bottomMargin));                //叠加当前行的宽度                lineWidth += childWidth;                //计算当前行最大高度                lineHight = Math.max(lineHight, childHight);            }            //加上最后一行的宽高的计算出ViewGroup需要的宽高            if (i == childCount - 1) {                width = Math.max(width, lineWidth);                hight += lineHight;            }        }        setMeasuredDimension(                widthMode == MeasureSpec.EXACTLY ? sizeWidth : width,                hightMode == MeasureSpec.EXACTLY ? sizeHight : hight        );    }    @Override    protected void onLayout(boolean changed, int l, int t, int r, int b) {        for (View key : map.keySet()) {            ChildViewPosition position = map.get(key);            key.layout(position.left, position.top, position.right, position.bottom);        }    }    private class ChildViewPosition {        public ChildViewPosition(int left, int top, int right, int bottom) {            this.left = left;            this.right = right;            this.top = top;            this.bottom = bottom;        }        int left;        int right;        int top;        int bottom;    }}

package com.ljh.flowviewgroup;import android.graphics.Color;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.view.Menu;import android.view.MenuItem;import android.view.View;import android.view.ViewGroup;import android.widget.Button;import android.widget.LinearLayout;import android.widget.TextView;public class MainActivity extends AppCompatActivity {    FlowViewGroup flowViewGroup;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        flowViewGroup = (FlowViewGroup) findViewById(R.id.flowViewGroup);        for (int i = 0; i < 20; i++) {            TextView text = new TextView(this);            text.setText(" texttext" + i + " ");            text.setBackgroundResource(R.drawable.round);            text.setPadding(10, 10, 10, 10);            flowViewGroup.addView(text);            ViewGroup.MarginLayoutParams lp = (ViewGroup.MarginLayoutParams) text.getLayoutParams();            lp.bottomMargin = 10;            lp.topMargin = 10;            lp.rightMargin = 10;            lp.leftMargin = 10;            text.setLayoutParams(lp);        }    }}

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:paddingBottom="@dimen/activity_vertical_margin"    android:paddingLeft="@dimen/activity_horizontal_margin"    android:paddingRight="@dimen/activity_horizontal_margin"    android:paddingTop="@dimen/activity_vertical_margin"    tools:context=".MainActivity">    <com.ljh.flowviewgroup.FlowViewGroup        android:id="@+id/flowViewGroup"        android:layout_width="wrap_content"        android:layout_height="wrap_content">    </com.ljh.flowviewgroup.FlowViewGroup></RelativeLayout>

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