FlowLayout

import java.util.ArrayList;

import com.ryan.googleplay.R;
import com.ryan.googleplay.utils.CommonUtil;

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

public class FlowLayout extends ViewGroup {

	private int mUsableWidth;
	private int mHorizontalSpace = CommonUtil.getDimension(R.dimen.dp_30);
	private int mVerticalSpace = CommonUtil.getDimension(R.dimen.dp_30);
	private ArrayList<Line> lineList = new ArrayList<FlowLayout.Line>();

	public FlowLayout(Context context, AttributeSet attrs, int defStyle) {
		super(context, attrs, defStyle);
	}

	public FlowLayout(Context context, AttributeSet attrs) {
		super(context, attrs);
	}

	public FlowLayout(Context context) {
		super(context);
	}

	@Override
	protected void onLayout(boolean changed, int l, int t, int r, int b) {
		int mPaddingLeft = getPaddingLeft();
		int mPaddingTop = getPaddingTop();
		// 遍历line集合
		for (int i = 0; i < lineList.size(); i++) {
			// 获取其中的line对象
			Line line = lineList.get(i);
			// 获取每行的留白空间
			int remainSpace = getRemainSpace(line);
			// 从第二行开始，每行的top总是比上一行的top多一个行高和垂直间距
			if (i > 0) {
				mPaddingTop += lineList.get(i - 1).getTotalHeight()
						+ mVerticalSpace;
			}
			// 从line中获取lineViews以便操作其中的view对象
			ArrayList<View> lineViews = line.lineViews;
			for (int j = 0; j < lineViews.size(); j++) {
				// 获取每个view对象
				View view = lineViews.get(j);
				// 获取每行每个view应该分得的空间
				float perSpace = (remainSpace * 1.0f / lineViews.size()) + 0.5f;
				// 获取当前view加入留白宽度后的相应测量模式的宽度值
				int widthMeasureSpec = MeasureSpec.makeMeasureSpec(
						(int) (view.getMeasuredWidth() + perSpace),
						MeasureSpec.EXACTLY);
				// 重新测量view
				view.measure(widthMeasureSpec, 0);
				// 当该view为每行的第一个view时的布局
				if (j == 0) {
					view.layout(mPaddingLeft, mPaddingTop,
							mPaddingLeft + view.getMeasuredWidth(), mPaddingTop
									+ view.getMeasuredHeight());
				} else {
					// 当该view为每行的非第一个view时的布局
					View preView = lineViews.get(j - 1);
					int left = preView.getRight() + mHorizontalSpace;
					view.layout(left, preView.getTop(),
							left + view.getMeasuredWidth(), preView.getBottom());
				}
			}
		}
	}

	@Override
	protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
		super.onMeasure(widthMeasureSpec, heightMeasureSpec);
		// 获取FlowLayout的宽度
		int width = MeasureSpec.getSize(widthMeasureSpec);
		// 获取可用宽度
		if (mUsableWidth == 0) {
			mUsableWidth = width - getPaddingLeft() - getPaddingRight();
		}
		// 创建Line对象
		Line line = new Line();
		// 遍历所有的子View
		for (int i = 0; i < getChildCount(); i++) {
			View childView = getChildAt(i);
			// 手动绘制view
			childView.measure(0, 0);
			// 判断是否为第一个子View
			if (i == 0) {
				// 若是就添加到line中
				line.addViewToLine(childView);
				// 判断当前子View的宽度加水平间距宽加之前的line的总宽是否超出了本行的可用宽度
			} else if (childView.getMeasuredWidth() + line.getTotalWidth()
					+ mHorizontalSpace > mUsableWidth) {
				// 若超出就将line添加到lineList中
				lineList.add(line);
				// 新建line对象并向其中添加view对象
				line = new Line();
				line.addViewToLine(childView);
			} else {
				// 若未超出就将当前的view添加到line中
				line.addViewToLine(childView);
			}
			// 判断是否为最后一个子View
			if (i == getChildCount() - 1) {
				// 若是,就将其所在的line添加到lineList中
				lineList.add(line);
			}
		}
		//将填充完毕的高度给FlowLayout设置回去
		int height = getPaddingTop() + getPaddingBottom();
		for (int i = 0; i < lineList.size(); i++) {
			height += lineList.get(i).getTotalHeight();
		}
		height += (lineList.size() - 1) * mVerticalSpace;
		setMeasuredDimension(width, height);
	}

	/**
	 * 获取每行的剩余留白空间
	 * 
	 * @return
	 */
	private int getRemainSpace(Line line) {
		return mUsableWidth - line.getTotalWidth();
	}

	class Line {
		public ArrayList<View> lineViews = new ArrayList<View>();
		public int totalWidth;
		public int totalHeight;

		/**
		 * 将view添加到lineViews的集合中
		 * 
		 * @return
		 */
		public void addViewToLine(View view) {
			if (!lineViews.contains(view)) {
				if (lineViews.size() == 1) {
					lineViews.add(view);
					totalWidth += view.getMeasuredWidth();
				} else {
					lineViews.add(view);
					totalWidth += mHorizontalSpace + view.getMeasuredWidth();
				}
				totalHeight = Math.max(totalHeight, view.getMeasuredHeight());
			}
		}

		/**
		 * 获取lineViews的集合
		 * 
		 * @return
		 */
		public ArrayList<View> getLineViews() {
			return lineViews;
		}

		/**
		 * 获取lineViews的宽度
		 * 
		 * @return
		 */
		public int getTotalWidth() {
			return totalWidth;
		}

		/**
		 * 获取lineViews的高度
		 * 
		 * @return
		 */
		public int getTotalHeight() {
			return totalHeight;
		}
	}

	/**
	 * 设置view的水平间距
	 * 
	 * @param mHorizontalSpace
	 */
	public void setHorizontalSpace(int mHorizontalSpace) {
		this.mHorizontalSpace = mHorizontalSpace;
	}

	/**
	 * 设置view的垂直间距
	 * 
	 * @param mHorizontalSpace
	 */
	public void setVerticallSpace(int mVerticalSpace) {
		this.mVerticalSpace = mVerticalSpace;
	}
}