// Either expand children with weight to take up available space or
// shrink them if they extend beyond our current bounds
int delta = heightSize - mTotalLength;
if (delta != 0 && totalWeight > 0.0f) {
float weightSum = mWeightSum > 0.0f ? mWeightSum : totalWeight;
mTotalLength = 0;
for (int i = 0; i < count; ++i) {
final View child = getVirtualChildAt(i);
if (child.getVisibility() == View.GONE) {
continue;
}
LinearLayout.LayoutParams lp = (LinearLayout.LayoutParams) child.getLayoutParams();
float childExtra = lp.weight;
if (childExtra > 0) {
// Child said it could absorb extra space -- give him his share
int share = (int) (childExtra * delta / weightSum);
weightSum -= childExtra;
delta -= share;
final int childWidthMeasureSpec = getChildMeasureSpec(widthMeasureSpec,
mPaddingLeft + mPaddingRight +
lp.leftMargin + lp.rightMargin, lp.width);
// TODO: Use a field like lp.isMeasured to figure out if this
// child has been previously measured
if ((lp.height != 0) || (heightMode != MeasureSpec.EXACTLY)) {
// child was measured once already above...
// base new measurement on stored values
int childHeight = child.getMeasuredHeight() + share;
if (childHeight < 0) {
childHeight = 0;
}
child.measure(childWidthMeasureSpec,
MeasureSpec.makeMeasureSpec(childHeight, MeasureSpec.EXACTLY));
} else {
// child was skipped in the loop above.
// Measure for this first time here
child.measure(childWidthMeasureSpec,
MeasureSpec.makeMeasureSpec(share > 0 ? share : 0,
MeasureSpec.EXACTLY));
}
// Child may now not fit in vertical dimension.
childState = combineMeasuredStates(childState, child.getMeasuredState()
& (MEASURED_STATE_MASK>>MEASURED_HEIGHT_STATE_SHIFT));
}
final int margin = lp.leftMargin + lp.rightMargin;
final int measuredWidth = child.getMeasuredWidth() + margin;
maxWidth = Math.max(maxWidth, measuredWidth);
boolean matchWidthLocally = widthMode != MeasureSpec.EXACTLY &&
lp.width == LayoutParams.MATCH_PARENT;
alternativeMaxWidth = Math.max(alternativeMaxWidth,
matchWidthLocally ? margin : measuredWidth);
allFillParent = allFillParent && lp.width == LayoutParams.MATCH_PARENT;
final int totalLength = mTotalLength;
mTotalLength = Math.max(totalLength, totalLength + child.getMeasuredHeight() +
lp.topMargin + lp.bottomMargin + getNextLocationOffset(child));
}
// Add in our padding
mTotalLength += mPaddingTop + mPaddingBottom;
// TODO: Should we recompute the heightSpec based on the new total length?
- 通过heightSize-mTotalLength得到delta，也就是还剩余的高度差，它有可能是负数
- 判断delta不为0并且totalWeight大于0，那么才开始进行多余空间的分配
- 判断mWeightSum是否大于0，这个属性是从外部设置的，如果没有设置的话，就会用自己算出来的totalWeight来作为总weight
- 开始遍历所有的子View，并且将空View或者Visible为GONE的子View排除
- 从子View的LayoutParams中获取lp.weight属性
- 通过计算share，来获取子View可以获得多少的剩余空间
- 通过getChildMeasureSpec获取子View的widthMeasureSpec
- 将上次measure出的子View高度再加上share的高度获取子View的新高度，再调用child.measure重新计算子View的新高度
- 通过child.getMeasuredWidth+margin获取最大的宽度
- 判断widthMode不为MeasureSpec.EXACTLY，并且lp.width为LayoutParams.MATCH_PARENT，那么alrtnativeMaxWidth就是margin
- 将mTotalLength再加上子View的高度，算出总共的高度
