FlowLayout流式布局

这就是FlowLayout的效果，我就复制粘贴了一下，提醒我LOL一定要超神，哈哈。

其实原理很简单，就是到一个控件的大小不够放了换下一行。

继承ViewGroup

我们要使用MarginLayoutParams

测量ViewGroup的大小,测量子view的大小得到viewGroupde 

@Override
	protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
		super.onMeasure(widthMeasureSpec, heightMeasureSpec);
		int sizeWidth = MeasureSpec.getSize(widthMeasureSpec);
		int modeWidth = MeasureSpec.getMode(widthMeasureSpec);

		int sizeHeight = MeasureSpec.getSize(heightMeasureSpec);
		int modeHeight = MeasureSpec.getMode(heightMeasureSpec);

		// wrapcontent
		int width = 0;
		int height = 0;

		int lineWidth = 0;
		int lineHeight = 0;

		int cCount = getChildCount();
		for (int i = 0; i < cCount; i++) {
			View child = getChildAt(i);
			measureChild(child, widthMeasureSpec, heightMeasureSpec);
			MarginLayoutParams lp = (MarginLayoutParams) child
					.getLayoutParams();
			int childWidth = child.getMeasuredWidth() + lp.leftMargin
					+ lp.rightMargin;
			int childHeight = child.getMeasuredHeight() + lp.topMargin
					+ lp.bottomMargin;

			if (lineWidth + childWidth > sizeWidth - getPaddingLeft()
					+ getPaddingRight()) {
				width = Math.max(width, lineWidth);
				// 重置lineWidth
				lineWidth = childWidth;
				// 记录行高
				height += childHeight;
				lineHeight = childHeight;

			} else {
				lineWidth += childWidth;
				lineHeight = Math.max(lineHeight, childHeight);
			}
			// 如果是最后一个控件
			if (i == cCount - 1) {
				width = Math.max(lineWidth, width);
				height += lineHeight;
			}

			setMeasuredDimension(modeWidth == MeasureSpec.EXACTLY ? sizeWidth
					: width + getPaddingLeft() + getPaddingRight(),
					modeHeight == MeasureSpec.EXACTLY ? sizeHeight : height
							+ getPaddingTop() + getPaddingBottom());

		}

	}

继承viewGroup必须为子view布局:

@Override
	protected void onLayout(boolean changed, int l, int t, int r, int b) {
		mAllViews.clear();
		mLineHeight.clear();

		// 当前ViewGroup的宽度
		int width = getWidth();

		int lineWidth = 0;
		int lineHeight = 0;

		List<View> lineViews = new ArrayList<View>();

		int cCount = getChildCount();

		for (int i = 0; i < cCount; i++) {
			View child = getChildAt(i);
			MarginLayoutParams lp = (MarginLayoutParams) child
					.getLayoutParams();

			int childWidth = child.getMeasuredWidth();
			int childHeight = child.getMeasuredHeight();

			// 如果需要换行
			if (childWidth + lineWidth + lp.leftMargin + lp.rightMargin > width
					- getPaddingLeft() - getPaddingRight()) {
				// 记录LineHeight
				mLineHeight.add(lineHeight);
				// 记录当前行的Views
				mAllViews.add(lineViews);

				// 重置我们的行宽和行高
				lineWidth = 0;
				lineHeight = childHeight + lp.topMargin + lp.bottomMargin;
				// 重置我们的View集合
				lineViews = new ArrayList<View>();
			}
			lineWidth += childWidth + lp.leftMargin + lp.rightMargin;
			lineHeight = Math.max(lineHeight, childHeight + lp.topMargin
					+ lp.bottomMargin);
			lineViews.add(child);

		}// for end
			// 处理最后一行
		mLineHeight.add(lineHeight);
		mAllViews.add(lineViews);

		// 设置子View的位置

		int left = getPaddingLeft();
		int top = getPaddingTop();

		// 行数
		int lineNum = mAllViews.size();

		for (int i = 0; i < lineNum; i++) {
			// 当前行的所有的View
			lineViews = mAllViews.get(i);
			lineHeight = mLineHeight.get(i);

			for (int j = 0; j < lineViews.size(); j++) {
				View child = lineViews.get(j);
				// 判断child的状态
				if (child.getVisibility() == View.GONE) {
					continue;
				}

				MarginLayoutParams lp = (MarginLayoutParams) child
						.getLayoutParams();

				int lc = left + lp.leftMargin;
				int tc = top + lp.topMargin;
				int rc = lc + child.getMeasuredWidth();
				int bc = tc + child.getMeasuredHeight();

				// 为子View进行布局
				child.layout(lc, tc, rc, bc);

				left += child.getMeasuredWidth() + lp.leftMargin
						+ lp.rightMargin;
			}
			left = getPaddingLeft();
			top += lineHeight;
		}

	}