自定义ViewGroup实现流式布局

package com.example.test;import android.content.Context;import android.util.AttributeSet;import android.view.View;import android.view.ViewGroup;public class FlowLayout extends ViewGroup {private int lineSpacing = 20;public FlowLayout(Context context, AttributeSet attrs) {super(context, attrs);}@Overrideprotected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {int widthSpecSize = MeasureSpec.getSize(widthMeasureSpec);int paddingLeft = getPaddingLeft();int paddingRight = getPaddingRight();int paddingTop = getPaddingTop();int paddingBottom = getPaddingBottom();int widthUsed = paddingLeft + paddingRight;int heightUsed = paddingTop + paddingBottom;int childMaxHeightOfThisLine = 0;int childCount = getChildCount();for (int i = 0; i < childCount; i++) {View child = getChildAt(i);if (child.getVisibility() != GONE) {int childUsedWidth = 0;int childUsedHeight = 0;measureChild(child, widthMeasureSpec, heightMeasureSpec);childUsedWidth += child.getMeasuredWidth();childUsedHeight += child.getMeasuredHeight();FlowLayoutParams params = (FlowLayoutParams) child.getLayoutParams();childUsedWidth += params.leftMargin + params.rightMargin;childUsedHeight += params.topMargin + params.bottomMargin;if (widthUsed + childUsedWidth < widthSpecSize) {widthUsed += childUsedWidth;if (childUsedHeight > childMaxHeightOfThisLine) {childMaxHeightOfThisLine = childUsedHeight;}} else {heightUsed += childMaxHeightOfThisLine + lineSpacing;widthUsed = paddingLeft + paddingRight + childUsedWidth;childMaxHeightOfThisLine = childUsedHeight;}}}heightUsed += childMaxHeightOfThisLine;setMeasuredDimension(widthSpecSize, heightUsed);}@Overrideprotected void onLayout(boolean changed, int l, int t, int r, int b) {int paddingLeft = getPaddingLeft();int paddingRight = getPaddingRight();int paddingTop = getPaddingTop();int childStartLayoutX = paddingLeft;int childStartLayoutY = paddingTop;int widthUsed = paddingLeft + paddingRight;int childMaxHeight = 0;int childCount = getChildCount();for (int i = 0; i < childCount; i++) {View child = getChildAt(i);if (child.getVisibility() != GONE) {int childNeededWidth, childNeedHeight;int left, top, right, bottom;int childMeasuredWidth = child.getMeasuredWidth();int childMeasuredHeight = child.getMeasuredHeight();FlowLayoutParams params = (FlowLayoutParams) child.getLayoutParams();int childLeftMargin = params.leftMargin;int childTopMargin = params.topMargin;int childRightMargin = params.rightMargin;int childBottomMargin = params.bottomMargin;childNeededWidth = childLeftMargin + childRightMargin+ childMeasuredWidth;childNeedHeight = childTopMargin + childBottomMargin+ childMeasuredHeight;if (widthUsed + childNeededWidth <= r - l) {if (childNeedHeight > childMaxHeight) {childMaxHeight = childNeedHeight;}} else {childStartLayoutY += childMaxHeight + lineSpacing;childStartLayoutX = paddingLeft;childMaxHeight = childNeedHeight;widthUsed = paddingLeft + paddingRight;}left = childStartLayoutX + childLeftMargin;top = childStartLayoutY + childTopMargin;right = left + childMeasuredWidth;bottom = top + childMeasuredHeight;widthUsed += childNeededWidth;childStartLayoutX += childNeededWidth;child.layout(left, top, right, bottom);}}}@Overrideprotected LayoutParams generateLayoutParams(LayoutParams p) {return new FlowLayoutParams(p);}@Overridepublic LayoutParams generateLayoutParams(AttributeSet attrs) {return new FlowLayoutParams(getContext(), attrs);}private class FlowLayoutParams extends MarginLayoutParams {public FlowLayoutParams(int arg0, int arg1) {super(arg0, arg1);}public FlowLayoutParams(LayoutParams arg0) {super(arg0);}public FlowLayoutParams(MarginLayoutParams arg0) {super(arg0);}public FlowLayoutParams(Context arg0, AttributeSet arg1) {super(arg0, arg1);}}}