安卓实现自定义ViewGroup

1 写一个类继承自ViewGroup

2 在onMeasure计算出ViewGroup占据的大小 也就是宽和高

3 接着在onLayout中在ViewGroup的宽高内一个一个摆放layout子View

下面看代码演示

package com.example.aaaa;

import android.content.Context;

import android.util.AttributeSet;

import android.util.Log;

import android.view.View;

import android.view.ViewGroup;

public class MyLayoutextends ViewGroup {

/**

* 这是必须要重写的 两个函数的构造方法 否则报错 原因可以看源码

* 通过构造函数两个参数反射生成View的

*

    * @param context

    * @param attrs

    */

    public MyLayout(Context context, AttributeSet attrs) {

super(context, attrs);

    }

@Override

    protected void onLayout(boolean changed, int l, int t, int r, int b) {

int count = getChildCount();

        for (int i =0; i < count; i++) {

View v = getChildAt(i);

            if (v.getVisibility() == View.VISIBLE) {

int childWidth = v.getMeasuredWidth();

                int childHeight = v.getMeasuredHeight();

                v.layout(l, t, l + childWidth, t + childHeight);

                l += childWidth;

                // t += childHeight;  这句放开可以竖向ViewGroup  //28 29行同时放开实现梯子形ViewGroup

            }

}

}

@Override

    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {

int measureWidth =0;

        int measureHeight =0;

        int count = getChildCount();

        for (int i =0; i < count; i++) {

View v = getChildAt(i);

            if (v.getVisibility() == View.VISIBLE) {

measureChild(v, widthMeasureSpec, heightMeasureSpec);

                measureHeight = Math.max(measureHeight, v.getMeasuredHeight());

                measureWidth += v.getMeasuredWidth();

//                measureWidth = Math.max(measureWidth, v.getMeasuredWidth());

//                measureHeight += v.getMeasuredHeight();  放开实现竖向ViewGroup

//                measureWidth += v.getMeasuredWidth();

//                measureWidth += v.getMeasuredWidth();  放开实现梯子形ViewGroup

            }

}

measureWidth += getPaddingLeft() + getPaddingRight();

        measureHeight += getPaddingTop() + getPaddingBottom();

        setMeasuredDimension(measureWidth, measureHeight);

        // super.onMeasure(widthMeasureSpec, heightMeasureSpec);

    }

}

效果如下，梯子形ViewGroup