流式布局

如果想要达到一种效果,向容器中添加控件,子控件会自动的换行.
这就是经常提到的流式布局.
主要的思路是类继承ViewGroup,然后重写其中的onMeasure方法与OnLayout方法.
用来确定控件的大小与每一个子控件的位置摆放.

本文转载
http://www.imooc.com/learn/237

public class TextFlowLayout extends ViewGroup {    public TextFlowLayout(Context context) {        super(context, null);    }    public TextFlowLayout(Context context, AttributeSet attrs) {        super(context, attrs);    }    public TextFlowLayout(Context context, AttributeSet attrs, int defStyle) {        super(context, attrs, defStyle);    }    @Override    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {        // 父控件传进来的宽度和高度以及对应的测量模式        int sizeWidth = MeasureSpec.getSize(widthMeasureSpec);        int modeWidth = MeasureSpec.getMode(widthMeasureSpec);        int sizeHeight = MeasureSpec.getSize(heightMeasureSpec);        int modeHeight = MeasureSpec.getMode(heightMeasureSpec);        // 如果当前ViewGroup的宽高为wrap_content的情况        int width = 0;// 自己测量的 宽度        int height = 0;// 自己测量的高度        // 记录每一行的宽度和高度        int lineWidth = 0;        int lineHeight = 0;        // 获取子view的个数        int childCount = getChildCount();        for (int i = 0; i < childCount; i++) {            View child = getChildAt(i);            // 测量子View的宽和高            measureChild(child, widthMeasureSpec, heightMeasureSpec);            // 得到LayoutParams            MarginLayoutParams lp = (MarginLayoutParams) getLayoutParams();            // 子View占据的宽度            int childWidth = child.getMeasuredWidth() + lp.leftMargin + lp.rightMargin;            // 子View占据的高度            int childHeight = child.getMeasuredHeight() + lp.topMargin + lp.bottomMargin;            // 换行时候            if (lineWidth + childWidth > sizeWidth) {                // 对比得到最大的宽度                width = Math.max(width, lineWidth);                // 重置lineWidth                lineWidth = childWidth;                // 记录行高                height += lineHeight;                lineHeight = childHeight;            } else {// 不换行情况                    // 叠加行宽                lineWidth += childWidth;                // 得到最大行高                lineHeight = Math.max(lineHeight, childHeight);            }            // 处理最后一个子View的情况            if (i == childCount - 1) {                width = Math.max(width, lineWidth);                height += lineHeight;            }        }        // wrap_content        setMeasuredDimension(modeWidth == MeasureSpec.EXACTLY ? sizeWidth : width,                modeHeight == MeasureSpec.EXACTLY ? sizeHeight : height);        super.onMeasure(widthMeasureSpec, heightMeasureSpec);    }    // 存储所有子View    private List<List<View>> mAllChildViews = new ArrayList<List<View>>();    // 每一行的高度    private List<Integer> mLineHeight = new ArrayList<Integer>();    @Override    protected void onLayout(boolean changed, int l, int t, int r, int b) {        // TODO Auto-generated method stub        mAllChildViews.clear();        mLineHeight.clear();        // 获取当前ViewGroup的宽度        int width = getWidth();        int lineWidth = 0;        int lineHeight = 0;        // 记录当前行的view        List<View> lineViews = new ArrayList<View>();        int childCount = getChildCount();        for (int i = 0; i < childCount; 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) {                // 记录LineHeight                mLineHeight.add(lineHeight);                // 记录当前行的Views                mAllChildViews.add(lineViews);                // 重置行的宽高                lineWidth = 0;                lineHeight = childHeight + lp.topMargin + lp.bottomMargin;                // 重置view的集合                lineViews = new ArrayList();            }            lineWidth += childWidth + lp.leftMargin + lp.rightMargin;            lineHeight = Math.max(lineHeight, childHeight + lp.topMargin + lp.bottomMargin);            lineViews.add(child);        }        // 处理最后一行        mLineHeight.add(lineHeight);        mAllChildViews.add(lineViews);        // 设置子View的位置        int left = 0;        int top = 0;        // 获取行数        int lineCount = mAllChildViews.size();        for (int i = 0; i < lineCount; i++) {            // 当前行的views和高度            lineViews = mAllChildViews.get(i);            lineHeight = mLineHeight.get(i);            for (int j = 0; j < lineViews.size(); j++) {                View child = lineViews.get(j);                // 判断是否显示                if (child.getVisibility() == View.GONE) {                    continue;                }                MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams();                int cLeft = left + lp.leftMargin;                int cTop = top + lp.topMargin;                int cRight = cLeft + child.getMeasuredWidth();                int cBottom = cTop + child.getMeasuredHeight();                // 进行子View进行布局                child.layout(cLeft, cTop, cRight, cBottom);                left += child.getMeasuredWidth() + lp.leftMargin + lp.rightMargin;            }            left = 0;            top += lineHeight;        }    }    /**     * 与当前ViewGroup对应的LayoutParams     */    @Override    public LayoutParams generateLayoutParams(AttributeSet attrs) {        return (LayoutParams) new MarginLayoutParams(getContext(), attrs);    }}