@Overrideprotected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {if (mDirtyHierarchy) {mDirtyHierarchy = false;sortChildren();}int myWidth = -1;int myHeight = -1;int width = 0;int height = 0;final int widthMode = MeasureSpec.getMode(widthMeasureSpec);final int heightMode = MeasureSpec.getMode(heightMeasureSpec);final int widthSize = MeasureSpec.getSize(widthMeasureSpec);final int heightSize = MeasureSpec.getSize(heightMeasureSpec);// Record our dimensions if they are known;if (widthMode != MeasureSpec.UNSPECIFIED) {myWidth = widthSize;}if (heightMode != MeasureSpec.UNSPECIFIED) {myHeight = heightSize;}if (widthMode == MeasureSpec.EXACTLY) {width = myWidth;}if (heightMode == MeasureSpec.EXACTLY) {height = myHeight;}View ignore = null;int gravity = mGravity & Gravity.RELATIVE_HORIZONTAL_GRAVITY_MASK;final boolean horizontalGravity = gravity != Gravity.START && gravity != 0;gravity = mGravity & Gravity.VERTICAL_GRAVITY_MASK;final boolean verticalGravity = gravity != Gravity.TOP && gravity != 0;int left = Integer.MAX_VALUE;int top = Integer.MAX_VALUE;int right = Integer.MIN_VALUE;int bottom = Integer.MIN_VALUE;boolean offsetHorizontalAxis = false;boolean offsetVerticalAxis = false;if ((horizontalGravity || verticalGravity) && mIgnoreGravity != View.NO_ID) {ignore = findViewById(mIgnoreGravity);}final boolean isWrapContentWidth = widthMode != MeasureSpec.EXACTLY;final boolean isWrapContentHeight = heightMode != MeasureSpec.EXACTLY;// We need to know our size for doing the correct computation of children positioning in RTL// mode but there is no practical way to get it instead of running the code below.// So, instead of running the code twice, we just set the width to a "default display width"// before the computation and then, as a last pass, we will update their real position with// an offset equals to "DEFAULT_WIDTH - width".final int layoutDirection = getLayoutDirection();if (isLayoutRtl() && myWidth == -1) {myWidth = DEFAULT_WIDTH;}View[] views = mSortedHorizontalChildren;int count = views.length;for (int i = 0; i < count; i++) {View child = views[i];if (child.getVisibility() != GONE) {LayoutParams params = (LayoutParams) child.getLayoutParams();int[] rules = params.getRules(layoutDirection);applyHorizontalSizeRules(params, myWidth, rules);measureChildHorizontal(child, params, myWidth, myHeight);if (positionChildHorizontal(child, params, myWidth, isWrapContentWidth)) {offsetHorizontalAxis = true;}}}views = mSortedVerticalChildren;count = views.length;final int targetSdkVersion = getContext().getApplicationInfo().targetSdkVersion;for (int i = 0; i < count; i++) {final View child = views[i];if (child.getVisibility() != GONE) {final LayoutParams params = (LayoutParams) child.getLayoutParams();applyVerticalSizeRules(params, myHeight, child.getBaseline());measureChild(child, params, myWidth, myHeight);if (positionChildVertical(child, params, myHeight, isWrapContentHeight)) {offsetVerticalAxis = true;}if (isWrapContentWidth) {if (isLayoutRtl()) {if (targetSdkVersion < Build.VERSION_CODES.KITKAT) {width = Math.max(width, myWidth - params.mLeft);} else {width = Math.max(width, myWidth - params.mLeft - params.leftMargin);}} else {if (targetSdkVersion < Build.VERSION_CODES.KITKAT) {width = Math.max(width, params.mRight);} else {width = Math.max(width, params.mRight + params.rightMargin);}}}if (isWrapContentHeight) {if (targetSdkVersion < Build.VERSION_CODES.KITKAT) {height = Math.max(height, params.mBottom);} else {height = Math.max(height, params.mBottom + params.bottomMargin);}}if (child != ignore || verticalGravity) {left = Math.min(left, params.mLeft - params.leftMargin);top = Math.min(top, params.mTop - params.topMargin);}if (child != ignore || horizontalGravity) {right = Math.max(right, params.mRight + params.rightMargin);bottom = Math.max(bottom, params.mBottom + params.bottomMargin);}}}// Use the top-start-most laid out view as the baseline. RTL offsets are// applied later, so we can use the left-most edge as the starting edge.View baselineView = null;LayoutParams baselineParams = null;for (int i = 0; i < count; i++) {final View child = views[i];if (child.getVisibility() != GONE) {final LayoutParams childParams = (LayoutParams) child.getLayoutParams();if (baselineView == null || baselineParams == null|| compareLayoutPosition(childParams, baselineParams) < 0) {baselineView = child;baselineParams = childParams;}}}mBaselineView = baselineView;if (isWrapContentWidth) {// Width already has left padding in it since it was calculated by looking at// the right of each child viewwidth += mPaddingRight;if (mLayoutParams != null && mLayoutParams.width >= 0) {width = Math.max(width, mLayoutParams.width);}width = Math.max(width, getSuggestedMinimumWidth());width = resolveSize(width, widthMeasureSpec);if (offsetHorizontalAxis) {for (int i = 0; i < count; i++) {final View child = views[i];if (child.getVisibility() != GONE) {final LayoutParams params = (LayoutParams) child.getLayoutParams();final int[] rules = params.getRules(layoutDirection);if (rules[CENTER_IN_PARENT] != 0 || rules[CENTER_HORIZONTAL] != 0) {centerHorizontal(child, params, width);} else if (rules[ALIGN_PARENT_RIGHT] != 0) {final int childWidth = child.getMeasuredWidth();params.mLeft = width - mPaddingRight - childWidth;params.mRight = params.mLeft + childWidth;}}}}}if (isWrapContentHeight) {// Height already has top padding in it since it was calculated by looking at// the bottom of each child viewheight += mPaddingBottom;if (mLayoutParams != null && mLayoutParams.height >= 0) {height = Math.max(height, mLayoutParams.height);}height = Math.max(height, getSuggestedMinimumHeight());height = resolveSize(height, heightMeasureSpec);if (offsetVerticalAxis) {for (int i = 0; i < count; i++) {final View child = views[i];if (child.getVisibility() != GONE) {final LayoutParams params = (LayoutParams) child.getLayoutParams();final int[] rules = params.getRules(layoutDirection);if (rules[CENTER_IN_PARENT] != 0 || rules[CENTER_VERTICAL] != 0) {centerVertical(child, params, height);} else if (rules[ALIGN_PARENT_BOTTOM] != 0) {final int childHeight = child.getMeasuredHeight();params.mTop = height - mPaddingBottom - childHeight;params.mBottom = params.mTop + childHeight;}}}}}if (horizontalGravity || verticalGravity) {final Rect selfBounds = mSelfBounds;selfBounds.set(mPaddingLeft, mPaddingTop, width - mPaddingRight,height - mPaddingBottom);final Rect contentBounds = mContentBounds;Gravity.apply(mGravity, right - left, bottom - top, selfBounds, contentBounds,layoutDirection);final int horizontalOffset = contentBounds.left - left;final int verticalOffset = contentBounds.top - top;if (horizontalOffset != 0 || verticalOffset != 0) {for (int i = 0; i < count; i++) {final View child = views[i];if (child.getVisibility() != GONE && child != ignore) {final LayoutParams params = (LayoutParams) child.getLayoutParams();if (horizontalGravity) {params.mLeft += horizontalOffset;params.mRight += horizontalOffset;}if (verticalGravity) {params.mTop += verticalOffset;params.mBottom += verticalOffset;}}}}}if (isLayoutRtl()) {final int offsetWidth = myWidth - width;for (int i = 0; i < count; i++) {final View child = views[i];if (child.getVisibility() != GONE) {final LayoutParams params = (LayoutParams) child.getLayoutParams();params.mLeft -= offsetWidth;params.mRight -= offsetWidth;}}}setMeasuredDimension(width, height);}

  @Overrideprotected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {if (mOrientation == VERTICAL) {measureVertical(widthMeasureSpec, heightMeasureSpec);} else {measureHorizontal(widthMeasureSpec, heightMeasureSpec);}}

LinearLayout

Measure：2.058ms
Layout：0.296ms
draw：3.857ms

FrameLayout

Measure：1.334ms
Layout：0.213ms
draw：3.680ms
从这个数据来使用LinearLayout，仅嵌套一个LinearLayou，在onMeasure就相关2倍时间和FrameLayout相比，layout和draw的过程两者相差无几，考虑到误差的问题，几乎可以认为两者不分伯仲

看下FrameLayout的源码，做了什么？

protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {int count = getChildCount();final boolean measureMatchParentChildren =MeasureSpec.getMode(widthMeasureSpec) != MeasureSpec.EXACTLY ||MeasureSpec.getMode(heightMeasureSpec) != MeasureSpec.EXACTLY;//当FrameLayout的宽和高，只有同时设置为match_parent或者指定的size，那么这个//measureMatchParentChlidren = false，否则为true。下面会用到这个变量mMatchParentChildren.clear();int maxHeight = 0;     int maxWidth = 0;int childState = 0;    //宽高的期望类型for (int i = 0; i < count; i++) {    //一次遍历每一个不为GONE的子viewfinal View child = getChildAt(i);    if (mMeasureAllChildren || child.getVisibility() != GONE) {//去掉FrameLayout的左右padding，子view的左右margin，这时候，再去//计算子view的期望的值measureChildWithMargins(child, widthMeasureSpec, 0, heightMeasureSpec, 0);final LayoutParams lp = (LayoutParams) child.getLayoutParams();/*maxWidth找到子View中最大的宽，高同理，为什么要找到他，因为在这里，FrameLayout是wrap-content.他的宽高肯定受子view的影响*/maxWidth = Math.max(maxWidth,child.getMeasuredWidth() + lp.leftMargin + lp.rightMargin);maxHeight = Math.max(maxHeight,child.getMeasuredHeight() + lp.topMargin + lp.bottomMargin);childState = combineMeasuredStates(childState, child.getMeasuredState());/*下面的判断，只有上面的FragLayout的width和height都设置为match_parent 才不会执行此处的mMatchParentChlidren的list里存的是设置为match_parent的子view。结合上面两句话的意思，当FrameLayout设置为wrap_content，这时候要把所有宽高设置为match_parent的子View都记录下来，记录下来干什么呢？这时候FrameLayout的宽高同时受子View的影响*/if (measureMatchParentChildren) {if (lp.width == LayoutParams.MATCH_PARENT ||lp.height == LayoutParams.MATCH_PARENT) {mMatchParentChildren.add(child);}}}}// Account for padding toomaxWidth += getPaddingLeftWithForeground() + getPaddingRightWithForeground();maxHeight += getPaddingTopWithForeground() + getPaddingBottomWithForeground();// Check against our minimum height and widthmaxHeight = Math.max(maxHeight, getSuggestedMinimumHeight());maxWidth = Math.max(maxWidth, getSuggestedMinimumWidth());// Check against our foreground's minimum height and widthfinal Drawable drawable = getForeground();if (drawable != null) {maxHeight = Math.max(maxHeight, drawable.getMinimumHeight());maxWidth = Math.max(maxWidth, drawable.getMinimumWidth());}//设置测量过的宽高setMeasuredDimension(resolveSizeAndState(maxWidth, widthMeasureSpec, childState),resolveSizeAndState(maxHeight, heightMeasureSpec,childState << MEASURED_HEIGHT_STATE_SHIFT));count = mMatchParentChildren.size();//这个大小就是子view中设定为match_parent的个数if (count > 1) {for (int i = 0; i < count; i++) {//这里看上去重新计算了一遍final View child = mMatchParentChildren.get(i);final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams();int childWidthMeasureSpec;int childHeightMeasureSpec;/*如果子view的宽是match_parent，则宽度期望值是总宽度-padding-margin如果子view的宽是指定的比如100dp，则宽度期望值是padding+margin+width这个很容易理解,下面的高同理*/if (lp.width == LayoutParams.MATCH_PARENT) {childWidthMeasureSpec = MeasureSpec.makeMeasureSpec(getMeasuredWidth() -getPaddingLeftWithForeground() - getPaddingRightWithForeground() -lp.leftMargin - lp.rightMargin,MeasureSpec.EXACTLY);} else {childWidthMeasureSpec = getChildMeasureSpec(widthMeasureSpec,getPaddingLeftWithForeground() + getPaddingRightWithForeground() +lp.leftMargin + lp.rightMargin,lp.width);}if (lp.height == LayoutParams.MATCH_PARENT) {childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(getMeasuredHeight() -getPaddingTopWithForeground() - getPaddingBottomWithForeground() -lp.topMargin - lp.bottomMargin,MeasureSpec.EXACTLY);} else {childHeightMeasureSpec = getChildMeasureSpec(heightMeasureSpec,getPaddingTopWithForeground() + getPaddingBottomWithForeground() +lp.topMargin + lp.bottomMargin,lp.height);}//把这部分子view重新计算大小child.measure(childWidthMeasureSpec, childHeightMeasureSpec);}}}

本文出自逆流的鱼：http://blog.csdn.net/hejjunlin/article/details/51159419
加了一个嵌套，onMeasure时间，多了将近一倍，原因在于：LinearLayout在某一方向onMeasure，发现还存在LinearLayout。将触发

 if (useLargestChild && (heightMode == MeasureSpec.AT_MOST || heightMode == MeasureSpec.UNSPECIFIED)) {mTotalLength = 0;for (int i = 0; i < count; ++i) {final View child = getVirtualChildAt(i);if (child == null) {mTotalLength += measureNullChild(i);continue;}if (child.getVisibility() == GONE) {i += getChildrenSkipCount(child, i);continue;}
}