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;
}
}
}

}