自定义ViewGroup实现自动换行的布局
viewgroup简单说就是可以装view的view.今天遇到一个问题，就是需要一个可以自动根据一行中view的宽度自动换行的布局，网上找了下，没有相关的例子，但是找到了思路：自定义一个viewgroup,然后在onlayout文件里面自动检测view的右边缘的横坐标值，和你的view的parent view的况度判断是否换行显示view就可以了。因为代码比较简单，就不多说了：
import android.content.Context;import android.util.AttributeSet;import android.view.View;import android.view.ViewGroup;/** * * @author RAW */public class FlowLayout extends ViewGroup { private final static int PAD_H = 2, PAD_V = 2; // Space between child views. private int mHeight; public FlowLayout(Context context) { super(context); } public FlowLayout(Context context, AttributeSet attrs) { super(context, attrs); } @Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { assert (MeasureSpec.getMode(widthMeasureSpec) != MeasureSpec.UNSPECIFIED); final int width = MeasureSpec.getSize(widthMeasureSpec) - getPaddingLeft() - getPaddingRight(); int height = MeasureSpec.getSize(heightMeasureSpec) - getPaddingTop() - getPaddingBottom(); final int count = getChildCount(); int xpos = getPaddingLeft(); int ypos = getPaddingTop(); int childHeightMeasureSpec; if(MeasureSpec.getMode(heightMeasureSpec) == MeasureSpec.AT_MOST) childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(height, MeasureSpec.AT_MOST); else childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED); mHeight = 0; for(int i = 0; i < count; i++) { final View child = getChildAt(i); if(child.getVisibility() != GONE) { child.measure(MeasureSpec.makeMeasureSpec(width, MeasureSpec.AT_MOST), childHeightMeasureSpec); final int childw = child.getMeasuredWidth(); mHeight = Math.max(mHeight, child.getMeasuredHeight() + PAD_V); if(xpos + childw > width) { xpos = getPaddingLeft(); ypos += mHeight; } xpos += childw + PAD_H; } } if(MeasureSpec.getMode(heightMeasureSpec) == MeasureSpec.UNSPECIFIED) { height = ypos + mHeight; } else if(MeasureSpec.getMode(heightMeasureSpec) == MeasureSpec.AT_MOST) { if(ypos + mHeight < height) { height = ypos + mHeight; } } height += 5; // Fudge to avoid clipping bottom of last row. setMeasuredDimension(width, height); } // end onMeasure() @Override protected void onLayout(boolean changed, int l, int t, int r, int b) { final int width = r - l; int xpos = getPaddingLeft(); int ypos = getPaddingTop(); for(int i = 0; i < getChildCount(); i++) { final View child = getChildAt(i); if(child.getVisibility() != GONE) { final int childw = child.getMeasuredWidth(); final int childh = child.getMeasuredHeight(); if(xpos + childw > width) { xpos = getPaddingLeft(); ypos += mHeight; } child.layout(xpos, ypos, xpos + childw, ypos + childh); xpos += childw + PAD_H; } } } // end onLayout()}