Android|Android -容器- FrameLayout
- 目录
Android -容器- FrameLayout
Android -容器- LinearLayout
Android -容器- RelativeLayout
- 【Android|Android -容器- FrameLayout】计算出所有的子View中最大的宽,高。因为FrameLayout中的每个View 在不同的层级,所有测量需要计算上,左右上下Margin,加上 FrameLayout自身的上下左右Padding,组成FrameLayout实际需要设置的宽高。
- 如果FragmeLayout本身宽,高不是MeasureSpec.EXACTLY,需要重新计算 设置了Match_Parent 的子View的大小。
//确定FrameLayout本身宽高是否为EXACTLY,该变量会导致某些子view再次绘制
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) {
//调用child.measure()
measureChildWithMargins(child, widthMeasureSpec, 0, heightMeasureSpec, 0);
final LayoutParams lp = (LayoutParams) child.getLayoutParams();
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());
//将高宽属性为MATCH_PARENT的子view进行保存
if (measureMatchParentChildren) {
if (lp.width == LayoutParams.MATCH_PARENT ||
lp.height == LayoutParams.MATCH_PARENT) {
mMatchParentChildren.add(child);
}
}
}
}
第二次measure:【在FrameLayout高或宽为wrap_content时,只对高或宽属性为match_parent的子view进行再次measure】
count = mMatchParentChildren.size();
//注意只有当count>1时,才会执行
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);
}child.measure(childWidthMeasureSpec, childHeightMeasureSpec);
}
}
例子:
Button_111的高度match_parent,会考虑Button_333的marginTop=300dp;Button_222的宽度match_parent,为Button_333的宽度200dp。
onLayout 流程
计算每个子View的layout_gravity,默认的layout_gravity 为Gravity.TOP | Gravity.LEFT,在根据Gravity计算时,通过水平方向的layout_gravity【CENTER_HORIZONTAL、RIGHT、LEFT】计算出childLeft,然后根据垂直方向layout_gravity 【CENTER_VERTICAL、TOP、BOTTOM】计算出childTop。
最后调用
child.layout(childLeft, childTop, childLeft + width, childTop + height);
推荐阅读
- Docker应用:容器间通信与Mariadb数据库主从复制
- android第三方框架(五)ButterKnife
- Android中的AES加密-下
- 带有Hilt的Android上的依赖注入
- android|android studio中ndk的使用
- Android事件传递源码分析
- RxJava|RxJava 在Android项目中的使用(一)
- Android7.0|Android7.0 第三方应用无法访问私有库
- 深入理解|深入理解 Android 9.0 Crash 机制(二)
- android防止连续点击的简单实现(kotlin)