Android 流式布局

public class XFlowLayout extends ViewGroup {

private int childHorizontalSpace;

private int childVerticalSpace;

private Map<Object, Location> mLocationMap;

public XFlowLayout(Context context, AttributeSet attrs) {

super(context, attrs);

TypedArray attrArray = context.obtainStyledAttributes(attrs, R.styleable.XLFlowLayout);

mLocationMap = new HashMap<>();

if (attrArray != null) {

childHorizontalSpace = attrArray.getDimensionPixelSize(R.styleable.XLFlowLayout_childHorizontalSpace, 0);

childVerticalSpace = attrArray.getDimensionPixelSize(R.styleable.XLFlowLayout_childVerticalSpace, 0);

attrArray.recycle();

}

}

@Override

protected LayoutParams generateLayoutParams(LayoutParams p) {

return new MarginLayoutParams(p);

}

@Override

public LayoutParams generateLayoutParams(AttributeSet attrs) {

return new MarginLayoutParams(getContext(), attrs);

}

@Override

protected LayoutParams generateDefaultLayoutParams() {

return new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);

}

/**

• 负责设置子控件的测量模式和大小 根据所有子控件设置自己的宽和高

*/

@Override

protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {

super.onMeasure(widthMeasureSpec, heightMeasureSpec);

if (mLocationMap != null && !mLocationMap.isEmpty()) {

mLocationMap.clear();

}

// 获得它的父容器为它设置的测量模式和大小

int sizeWidth = MeasureSpec.getSize(widthMeasureSpec);

int sizeHeight = MeasureSpec.getSize(heightMeasureSpec);

int modeWidth = MeasureSpec.getMode(widthMeasureSpec);

int modeHeight = MeasureSpec.getMode(heightMeasureSpec);

// 如果是 warp_content 情况下，记录宽和高

int width = 0;

int height = 0;

/**

• 记录每一行的宽度，width 不断取最大宽度

*/

int lineWidth = 0;

/**

• 每一行的高度，累加至 height

*/

int lineHeight = 0;

int count = getChildCount();

int left = getPaddingLeft();

int top = getPaddingTop();

// 遍历每个子元素

for (int i = 0; i < count; i++) {

View child = getChildAt(i);

if (child.getVisibility() == GONE)

continue;

// 测量每一个 child 的宽和高

measureChild(child, widthMeasureSpec, heightMeasureSpec);

// 得到 child 的 lp

LayoutParams lp = child.getLayoutParams();

// 当前子空间实际占据的宽度

int childWidth = child.getMeasuredWidth() + childHorizontalSpace;

// 当前子空间实际占据的高度

int childHeight = child.getMeasuredHeight() + childVerticalSpace;

if (lp != null && lp instanceof MarginLayoutParams) {

MarginLayoutParams params = (MarginLayoutParams) lp;

childWidth += params.leftMargin + params.rightMargin;

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}

/**

• 如果加入当前 child 的宽度，超出了最大宽度，则的到目前最大宽度给 width，累加 height 然后开启新行

*/

if (lineWidth + childWidth > sizeWidth - getPaddingLeft() - getPaddingRight()) {

width = Math.max(lineWidth, childWidth);// 取最大的

lineWidth = childWidth; // 重新开启新行，开始记录

// 叠加当前高度，

height += lineHeight;

// 开启记录下一行的高度

lineHeight = childHeight;

mLocationMap.put(child, new Location(left, top + height, childWidth + left - childHorizontalSpace, height +

child.getMeasuredHeight() + top));

} else {// 否则累加值 lineWidth,lineHeight 取最大高度

mLocationMap.put(child, new Location(lineWidth + left, top + height, lineWidth + childWidth -

childHorizontalSpace + left, height + child.getMeasuredHeight() + top));

lineWidth += childWidth;

lineHeight = Math.max(lineHeight, childHeight);

}

}

width = Math.max(width, lineWidth) + getPaddingLeft() + getPaddingRight();

height += lineHeight;

sizeHeight += getPaddingTop() + getPaddingBottom();

height += getPaddingTop() + getPaddingBottom();

setMeasuredDimension((modeWidth == MeasureSpec.EXACTLY) ? sizeWidth : width, (modeHeight == MeasureSpec.EXACTLY) ?

sizeHeight : height);

}