?FrameLaout 測量

@Overrideprotected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {int count = getChildCount();final boolean measureMatchParentChildren =MeasureSpec.getMode(widthMeasureSpec) != MeasureSpec.EXACTLY ||MeasureSpec.getMode(heightMeasureSpec) != MeasureSpec.EXACTLY;mMatchParentChildren.clear();int maxHeight = 0;int maxWidth = 0;int childState = 0;for (int i = 0; i < count; i++) {final View child = getChildAt(i);if (mMeasureAllChildren || child.getVisibility() != GONE) {//測量子view 調用子view的onMeasuremeasureChildWithMargins(child, widthMeasureSpec, 0, heightMeasureSpec, 0);final LayoutParams lp = (LayoutParams) child.getLayoutParams();//測量后可以得到子view的真正尺寸measuredWidth()//FrameLayout如果是wrapcontent的話就會使用子view中最大的子view尺寸 所以要記錄最大值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());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());}//設置自己的尺寸setMeasuredDimension(resolveSizeAndState(maxWidth, widthMeasureSpec, childState),resolveSizeAndState(maxHeight, heightMeasureSpec,childState << MEASURED_HEIGHT_STATE_SHIFT));//知道自己的尺寸后 再讓那些match_parent的子view 根據自己的尺寸 從新測量count = mMatchParentChildren.size();if (count > 1) {for (int i = 0; i < count; i++) {final View child = mMatchParentChildren.get(i);final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams();final int childWidthMeasureSpec;if (lp.width == LayoutParams.MATCH_PARENT) {final int width = Math.max(0, getMeasuredWidth()- getPaddingLeftWithForeground() - getPaddingRightWithForeground()- lp.leftMargin - lp.rightMargin);childWidthMeasureSpec = MeasureSpec.makeMeasureSpec(width, MeasureSpec.EXACTLY);} else {childWidthMeasureSpec = getChildMeasureSpec(widthMeasureSpec,getPaddingLeftWithForeground() + getPaddingRightWithForeground() +lp.leftMargin + lp.rightMargin,lp.width);}final int childHeightMeasureSpec;if (lp.height == LayoutParams.MATCH_PARENT) {final int height = Math.max(0, getMeasuredHeight()- getPaddingTopWithForeground() - getPaddingBottomWithForeground()- lp.topMargin - lp.bottomMargin);childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(height, MeasureSpec.EXACTLY);} else {childHeightMeasureSpec = getChildMeasureSpec(heightMeasureSpec,getPaddingTopWithForeground() + getPaddingBottomWithForeground() +lp.topMargin + lp.bottomMargin,lp.height);}//從新測量match parent的子view的尺寸child.measure(childWidthMeasureSpec, childHeightMeasureSpec);}}} @Overrideprotected void onLayout(boolean changed, int left, int top, int right, int bottom) {layoutChildren(left, top, right, bottom, false /* no force left gravity */);}void layoutChildren(int left, int top, int right, int bottom, boolean forceLeftGravity) {final int count = getChildCount();final int parentLeft = getPaddingLeftWithForeground();final int parentRight = right - left - getPaddingRightWithForeground();final int parentTop = getPaddingTopWithForeground();final int parentBottom = bottom - top - getPaddingBottomWithForeground();//放置比較簡單 因為是FrameLayout 子view之間不存在排列關系for (int i = 0; i < count; i++) {final View child = getChildAt(i);if (child.getVisibility() != GONE) {final LayoutParams lp = (LayoutParams) child.getLayoutParams();final int width = child.getMeasuredWidth();final int height = child.getMeasuredHeight();int childLeft;int childTop;int gravity = lp.gravity;if (gravity == -1) {gravity = DEFAULT_CHILD_GRAVITY;}final int layoutDirection = getLayoutDirection();final int absoluteGravity = Gravity.getAbsoluteGravity(gravity, layoutDirection);final int verticalGravity = gravity & Gravity.VERTICAL_GRAVITY_MASK;switch (absoluteGravity & Gravity.HORIZONTAL_GRAVITY_MASK) {case Gravity.CENTER_HORIZONTAL:childLeft = parentLeft + (parentRight - parentLeft - width) / 2 +lp.leftMargin - lp.rightMargin;break;case Gravity.RIGHT:if (!forceLeftGravity) {childLeft = parentRight - width - lp.rightMargin;break;}case Gravity.LEFT:default:childLeft = parentLeft + lp.leftMargin;}switch (verticalGravity) {case Gravity.TOP:childTop = parentTop + lp.topMargin;break;case Gravity.CENTER_VERTICAL:childTop = parentTop + (parentBottom - parentTop - height) / 2 +lp.topMargin - lp.bottomMargin;break;case Gravity.BOTTOM:childTop = parentBottom - height - lp.bottomMargin;break;default:childTop = parentTop + lp.topMargin;}//調用子view的放置方法child.layout(childLeft, childTop, childLeft + width, childTop + height);}}}

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