Android中自定义view实现流式布局

实现效果:

一.布局文件

二.自定义类
public class FlowLayout extends ViewGroup {

public FlowLayout(Context context) {
    this(context, null);
}

public FlowLayout(Context context, AttributeSet attrs) {
    this(context, attrs, 0);
}

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

private List> mLineViews = new ArrayList>();
private List mLineHeight = new ArrayList();

/**
 * 测量所有子View大小,确定ViewGroup的宽高
 *
 * @param widthMeasureSpec
 * @param heightMeasureSpec
 */
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    super.onMeasure(widthMeasureSpec, heightMeasureSpec);

    //由于onMeasure会执行多次,避免重复的计算控件个数和高度,这里需要进行清空操作
    mLineViews.clear();
    mLineHeight.clear();

    //获取测量的模式和尺寸大小
    int widthMode = MeasureSpec.getMode(widthMeasureSpec);
    int widthSize = MeasureSpec.getSize(widthMeasureSpec) - getPaddingLeft() - getPaddingRight();
    int heightMode = MeasureSpec.getMode(heightMeasureSpec);
    int heightSize = MeasureSpec.getSize(heightMeasureSpec) + getPaddingTop() + getPaddingBottom();


    //记录ViewGroup真实的测量宽高
    int viewGroupWidth = 0 - getPaddingLeft() - getPaddingRight();
    int viewGroupHeight = getPaddingTop() + getPaddingBottom();

    if (widthMode == MeasureSpec.EXACTLY && heightMode == MeasureSpec.EXACTLY) {
        viewGroupWidth = widthSize;
        viewGroupHeight = heightSize;
    } else {
        //当前所占的宽高
        int currentLineWidth = 0;
        int currentLineHeight = 0;

        //用来存储每一行上的子View
        List lineView = new ArrayList();
        int childViewsCount = getChildCount();
        for (int i = 0; i < childViewsCount; i++) {
            View childView = getChildAt(i);
            //对子View进行测量
            measureChild(childView, widthMeasureSpec, heightMeasureSpec);
            MarginLayoutParams marginLayoutParams = (MarginLayoutParams) childView.getLayoutParams();
            int childViewWidth = childView.getMeasuredWidth() + marginLayoutParams.leftMargin + marginLayoutParams.rightMargin;
            int childViewHeight = childView.getMeasuredHeight() + marginLayoutParams.topMargin + marginLayoutParams.bottomMargin;

            if (currentLineWidth + childViewWidth > widthSize) {
                //当前行宽+子View+左右外边距>ViewGroup的宽度,换行
                viewGroupWidth = Math.max(currentLineWidth, widthSize);
                viewGroupHeight += currentLineHeight;
                //添加行高
                mLineHeight.add(currentLineHeight);
                //添加行对象
                mLineViews.add(lineView);

                //new新的一行
                lineView = new ArrayList();
                //添加行对象里的子View
                lineView.add(childView);
                currentLineWidth = childViewWidth;

            } else {
                //当前行宽+子View+左右外边距<=ViewGroup的宽度,不换行
                currentLineWidth += childViewWidth;
                currentLineHeight = Math.max(currentLineHeight, childViewHeight);
                //添加行对象里的子View
                lineView.add(childView);
            }


            if (i == childViewsCount - 1) {
                //最后一个子View的时候
                //添加行对象
                mLineViews.add(lineView);
                viewGroupWidth = Math.max(childViewWidth, viewGroupWidth);
                viewGroupHeight += childViewHeight;
                //添加行高
                mLineHeight.add(currentLineHeight);

            }
        }

    }

    setMeasuredDimension(viewGroupWidth, viewGroupHeight);

}

/**
 * 设置ViewGroup里子View的具体位置
 *
 * @param changed
 * @param l
 * @param t
 * @param r
 * @param b
 */
@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {

    int left = getPaddingLeft();
    int top = getPaddingTop();
    //一共有几行
    int lines = mLineViews.size();
    for (int i = 0; i < lines; i++) {
        //每行行高
        int lineHeight = mLineHeight.get(i);
        //行内有几个子View
        List viewList = mLineViews.get(i);
        int views = viewList.size();

        for (int j = 0; j < views; j++) {
            View view = viewList.get(j);
            MarginLayoutParams marginLayoutParams = (MarginLayoutParams) view.getLayoutParams();
            int vl = left + marginLayoutParams.leftMargin;
            int vt = top + marginLayoutParams.topMargin;
            int vr = vl + view.getMeasuredWidth();
            int vb = vt + view.getMeasuredHeight();
            view.layout(vl, vt, vr, vb);
            left += view.getMeasuredWidth() + marginLayoutParams.leftMargin + marginLayoutParams.rightMargin;
        }
        left = getPaddingLeft();
        top += lineHeight;

    }
}

/**
 * 指定ViewGroup的LayoutParams
 *
 * @param attrs
 * @return
 */
@Override
public LayoutParams generateLayoutParams(AttributeSet attrs) {
    return new MarginLayoutParams(getContext(), attrs);
 	 }
  }