流式布局之FlowLayout使用

package com.a520it.mygoogleplay.ui;

import android.content.Context;
import android.util.AttributeSet;
import android.view.View;
import android.view.ViewGroup;

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

public class FlowLayout extends ViewGroup
{
private List mLines = new ArrayList(); // 用来记录描述有多少行View
private Line mCurrrenLine; // 用来记录当前已经添加到了哪一行
private int mHorizontalSpace = 10;
private int mVerticalSpace = 10;

public FlowLayout(Context context, AttributeSet attrs) {
    super(context, attrs);
    // TODO Auto-generated constructor stub
}

public FlowLayout(Context context) {
    super(context);
    // TODO Auto-generated constructor stub
}

public void setSpace(int horizontalSpace, int verticalSpace)
{
    this.mHorizontalSpace = horizontalSpace;
    this.mVerticalSpace = verticalSpace;
}

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec)
{
    // 清空
    mLines.clear();
    mCurrrenLine = null;

    int layoutWidth = MeasureSpec.getSize(widthMeasureSpec);

    // 获取行最大的宽度
    int maxLineWidth = layoutWidth - getPaddingLeft() - getPaddingRight();

    // 测量孩子
    int count = getChildCount();
    for (int i = 0; i < count; i++)
    {
        View view = getChildAt(i);

        // 如果孩子不可见
        if (view.getVisibility() == View.GONE)
        {
            continue;
        }

        // 测量孩子
        measureChild(view, widthMeasureSpec, heightMeasureSpec);

        // 往lines添加孩子
        if (mCurrrenLine == null)
        {
            // 说明还没有开始添加孩子
            mCurrrenLine = new Line(maxLineWidth, mHorizontalSpace);

            // 添加到 Lines中
            mLines.add(mCurrrenLine);

            // 行中一个孩子都没有
            mCurrrenLine.addView(view);
        }
        else
        {
            // 行不为空,行中有孩子了
            boolean canAdd = mCurrrenLine.canAdd(view);
            if (canAdd)
            {
                // 可以添加
                mCurrrenLine.addView(view);
            }
            else
            {
                // 不可以添加,装不下去
                // 换行

                // 新建行
                mCurrrenLine = new Line(maxLineWidth, mHorizontalSpace);
                // 添加到lines中
                mLines.add(mCurrrenLine);
                // 将view添加到line
                mCurrrenLine.addView(view);
            }
        }
    }

    // 设置自己的宽度和高度
    int measuredWidth = layoutWidth;
    // paddingTop + paddingBottom + 所有的行间距 + 所有的行的高度

    float allHeight = 0;
    for (int i = 0; i < mLines.size(); i++)
    {
        float mHeigth = mLines.get(i).mHeigth;

        // 加行高
        allHeight += mHeigth;
        // 加间距
        if (i != 0)
        {
            allHeight += mVerticalSpace;
        }
    }

    int measuredHeight = (int) (allHeight + getPaddingTop() + getPaddingBottom() + 0.5f);
    setMeasuredDimension(measuredWidth, measuredHeight);
}

@Override
protected void onLayout(boolean changed, int l, int t, int r, int b)
{
    // 给Child 布局---> 给Line布局

    int paddingLeft = getPaddingLeft();
    int offsetTop = getPaddingTop();
    for (int i = 0; i < mLines.size(); i++)
    {
        Line line = mLines.get(i);

        // 给行布局
        line.layout(paddingLeft, offsetTop);

        offsetTop += line.mHeigth + mVerticalSpace;
    }
}

class Line
{
    // 属性
    private List<View>  mViews  = new ArrayList<View>();    // 用来记录每一行有几个View
    private float       mMaxWidth;                          // 行最大的宽度
    private float       mUsedWidth;                     // 已经使用了多少宽度
    private float       mHeigth;                            // 行的高度
    private float       mMarginLeft;
    private float       mMarginRight;
    private float       mMarginTop;
    private float       mMarginBottom;
    private float       mHorizontalSpace;                   // View和view之间的水平间距

    // 构造
    public Line(int maxWidth, int horizontalSpace) {
        this.mMaxWidth = maxWidth;
        this.mHorizontalSpace = horizontalSpace;
    }

    // 方法
    /**
     * 添加view，记录属性的变化
     * 
     * @param view
     */
    public void addView(View view)
    {
        // 加载View的方法

        int size = mViews.size();
        int viewWidth = view.getMeasuredWidth();
        int viewHeight = view.getMeasuredHeight();
        // 计算宽和高
        if (size == 0)
        {
            // 说还没有添加View
            if (viewWidth > mMaxWidth)
            {
                mUsedWidth = mMaxWidth;
            }
            else
            {
                mUsedWidth = viewWidth;
            }
            mHeigth = viewHeight;
        }
        else
        {
            // 多个view的情况
            mUsedWidth += viewWidth + mHorizontalSpace;
            mHeigth = mHeigth < viewHeight ? viewHeight : mHeigth;
        }

        // 将View记录到集合中
        mViews.add(view);
    }

    /**
     * 用来判断是否可以将View添加到line中
     * 
     * @param view
     * @return
     */
    public boolean canAdd(View view)
    {
        // 判断是否能添加View

        int size = mViews.size();

        if (size == 0) { return true; }

        int viewWidth = view.getMeasuredWidth();

        // 预计使用的宽度
        float planWidth = mUsedWidth + mHorizontalSpace + viewWidth;

        if (planWidth > mMaxWidth)
        {
            // 加不进去
            return false;
        }

        return true;
    }

    /**
     * 给孩子布局
     * 
     * @param offsetLeft
     * @param offsetTop
     */
    public void layout(int offsetLeft, int offsetTop)
    {
        // 给孩子布局

        int currentLeft = offsetLeft;

        int size = mViews.size();
        // 判断已经使用的宽度是否小于最大的宽度
        float extra = 0;
        float widthAvg = 0;
        if (mMaxWidth > mUsedWidth)
        {
            extra = mMaxWidth - mUsedWidth;
            widthAvg = extra / size;
        }

        for (int i = 0; i < size; i++)
        {
            View view = mViews.get(i);
            int viewWidth = view.getMeasuredWidth();
            int viewHeight = view.getMeasuredHeight();

            // 判断是否有富余
            if (widthAvg != 0)
            {
                // 改变宽度
                int newWidth = (int) (viewWidth + widthAvg + 0.5f);
                int widthMeasureSpec = MeasureSpec.makeMeasureSpec(newWidth, MeasureSpec.EXACTLY);
                int heightMeasureSpec = MeasureSpec.makeMeasureSpec(viewHeight, MeasureSpec.EXACTLY);
                view.measure(widthMeasureSpec, heightMeasureSpec);

                viewWidth = view.getMeasuredWidth();
                viewHeight = view.getMeasuredHeight();
            }

            // 布局
            int left = currentLeft;
            int top = (int) (offsetTop + (mHeigth - viewHeight) / 2 +
                        0.5f);
            // int top = offsetTop;
            int right = left + viewWidth;
            int bottom = top + viewHeight;
            view.layout(left, top, right, bottom);

            currentLeft += viewWidth + mHorizontalSpace;
        }
    }
}

}