Android View的重绘过程之Layout
博客首页:http://www.cnblogs.com/kezhuang/p/
View绘制的三部曲,测量,布局,绘画
现在我们分析布局部分
测量部分在上篇文章中已经分析过了。不了解的可以去我的博客里找一下
View的布局和测量一样,都是从ViewRootImpl中发起,ViewRootImpl先通过measure来初始化整个的view树
之后会调用onLayout方法来布局,ViewRootImpl是通过performLayout函数来发起重绘的
比较重要的部分我会写注释,注意看注释就行
private void performLayout(WindowManager.LayoutParams lp, int desiredWindowWidth, int desiredWindowHeight) { mLayoutRequested = false; mScrollMayChange = true; mInLayout = true; final View host = mView; if (DEBUG_ORIENTATION || DEBUG_LAYOUT) { Log.v(TAG, "Laying out " + host + " to (" + host.getMeasuredWidth() + ", " + host.getMeasuredHeight() + ")"); } Trace.traceBegin(Trace.TRACE_TAG_VIEW, "layout"); try { //通过调用DecorView的layout函数,来发起整个view视图的重绘 host.layout(0, 0, host.getMeasuredWidth(), host.getMeasuredHeight()); mInLayout = false; int numViewsRequestingLayout = mLayoutRequesters.size(); if (numViewsRequestingLayout > 0) { // requestLayout() was called during layout. // If no layout-request flags are set on the requesting views, there is no problem. // If some requests are still pending, then we need to clear those flags and do // a full request/measure/layout pass to handle this situation. ArrayList<View> validLayoutRequesters = getValidLayoutRequesters(mLayoutRequesters, false); if (validLayoutRequesters != null) { // Set this flag to indicate that any further requests are happening during // the second pass, which may result in posting those requests to the next // frame instead mHandlingLayoutInLayoutRequest = true; // Process fresh layout requests, then measure and layout int numValidRequests = validLayoutRequesters.size(); for (int i = 0; i < numValidRequests; ++i) { final View view = validLayoutRequesters.get(i); Log.w("View", "requestLayout() improperly called by " + view + " during layout: running second layout pass"); view.requestLayout(); } measureHierarchy(host, lp, mView.getContext().getResources(), desiredWindowWidth, desiredWindowHeight); mInLayout = true; host.layout(0, 0, host.getMeasuredWidth(), host.getMeasuredHeight()); mHandlingLayoutInLayoutRequest = false; // Check the valid requests again, this time without checking/clearing the // layout flags, since requests happening during the second pass get noop'd validLayoutRequesters = getValidLayoutRequesters(mLayoutRequesters, true); if (validLayoutRequesters != null) { final ArrayList<View> finalRequesters = validLayoutRequesters; // Post second-pass requests to the next frame getRunQueue().post(new Runnable() { @Override public void run() { int numValidRequests = finalRequesters.size(); for (int i = 0; i < numValidRequests; ++i) { final View view = finalRequesters.get(i); Log.w("View", "requestLayout() improperly called by " + view + " during second layout pass: posting in next frame"); view.requestLayout(); } } }); } } } } finally { Trace.traceEnd(Trace.TRACE_TAG_VIEW); } mInLayout = false; }
这个函数主要功能就是调用view的layout方法,接下来要分析的就是layout函数了。这个函数在View中,是触发onLayout函数的方法
@SuppressWarnings({"unchecked"}) public void layout(int l, int t, int r, int b) { //先判断一下是否需要重新测量 if ((mPrivateFlags3 & PFLAG3_MEASURE_NEEDED_BEFORE_LAYOUT) != 0) { onMeasure(mOldWidthMeasureSpec, mOldHeightMeasureSpec); mPrivateFlags3 &= ~PFLAG3_MEASURE_NEEDED_BEFORE_LAYOUT; } int oldL = mLeft; int oldT = mTop; int oldB = mBottom; int oldR = mRight; //判断是否使用 optical bound 布局,并且绘制Frame出来 boolean changed = isLayoutModeOptical(mParent) ? setOpticalFrame(l, t, r, b) : setFrame(l, t, r, b); //如果需要重新layout的话,就开始调用DecorView的onLayout方法,我们简单看一下 if (changed || (mPrivateFlags & PFLAG_LAYOUT_REQUIRED) == PFLAG_LAYOUT_REQUIRED) { onLayout(changed, l, t, r, b); mPrivateFlags &= ~PFLAG_LAYOUT_REQUIRED; ListenerInfo li = mListenerInfo; if (li != null && li.mOnLayoutChangeListeners != null) { ArrayList<OnLayoutChangeListener> listenersCopy = (ArrayList<OnLayoutChangeListener>)li.mOnLayoutChangeListeners.clone(); int numListeners = listenersCopy.size(); for (int i = 0; i < numListeners; ++i) { listenersCopy.get(i).onLayoutChange(this, l, t, r, b, oldL, oldT, oldR, oldB); } } } mPrivateFlags &= ~PFLAG_FORCE_LAYOUT; mPrivateFlags3 |= PFLAG3_IS_LAID_OUT; }
这个函数的工作就是分发整个的布局流程,先是DecorView,在FrameLayout ....直到整个view tree布局完毕
@Override protected void onLayout(boolean changed, int left, int top, int right, int bottom) { super.onLayout(changed, left, top, right, bottom); //获取界面的边框如果有偏移,就需要偏移一下view窗口 getOutsets(mOutsets); if (mOutsets.left > 0) { offsetLeftAndRight(-mOutsets.left); } if (mOutsets.top > 0) { offsetTopAndBottom(-mOutsets.top); } }
这个onLayout是在DecorView中,他调用了super,也就是FrameLayout下边的onLayout方法,我们在继续看FrameLayout
/** * {@inheritDoc} */ @Override protected void onLayout(boolean changed, int left, int top, int right, int bottom) { layoutChildren(left, top, right, bottom, false /* no force left gravity */); }
这个函数页很简单,直接调用了layoutChildren方法去布局各种子view
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(); //开始布局,目前这个是FrameLayout,特性就是默认左上角,且会z轴覆盖 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; //处理对齐方式 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; } //布局子view,以此类推,会布局完整个view树 child.layout(childLeft, childTop, childLeft + width, childTop + height); } } }
上面方法运行完后,整个的布局过程就结束了。view这块的设计非常棒,采用了组合模式去设计,在上边循环中去调用layout方法,layout在去触发子view的onLayout来按照各自的规则去布局,直到整个view树循环完毕
Android View的重绘过程之Layout的更多相关文章
- Android View的重绘过程之WindowManager的addView方法
博客首页:http://www.cnblogs.com/kezhuang/p/ 关于Activity的contentView的构建过程,我在我的博客中已经分析过了,不了解的可以去看一下 <[An ...
- Android View的重绘过程之Draw
博客首页:http://www.cnblogs.com/kezhuang/p/ View绘制的三部曲,测量,布局,绘画现在我们分析绘画部分测量和布局 在前两篇文章中已经分析过了.不了解的可以去我的博客 ...
- Android View的重绘过程之Measure
博客首页:http://www.cnblogs.com/kezhuang/p/ View绘制的三部曲, 测量,布局,绘画今天我们分析测量过程 view的测量是从ViewRootImpl发起的,Vie ...
- [Android FrameWork 6.0源码学习] View的重绘过程之Layout
View绘制的三部曲,测量,布局,绘画现在我们分析布局部分测量部分在上篇文章中已经分析过了.不了解的可以去我的博客里找一下 View的布局和测量一样,都是从ViewRootImpl中发起,ViewRo ...
- [Android FrameWork 6.0源码学习] View的重绘过程之WindowManager的addView方法
博客首页:http://www.cnblogs.com/kezhuang/p/关于Activity的contentView的构建过程,我在我的博客中已经分析过了,不了解的可以去看一下<[Andr ...
- [Android FrameWork 6.0源码学习] View的重绘过程之Draw
View绘制的三部曲,测量,布局,绘画现在我们分析绘画部分测量和布局 在前两篇文章中已经分析过了.不了解的可以去我的博客里找一下 下面进入正题,开始分析调用以及函数原理 private void pe ...
- Android View的重绘ViewRootImpl的setView方法
博客首页:http://www.cnblogs.com/kezhuang/p/ 本篇文章来分析一下WindowManager的后续工作,也就是ViewRootImpl的setView函数的工作 /i* ...
- [Android FrameWork 6.0源码学习] View的重绘过程
View绘制的三部曲, 测量,布局,绘画今天我们分析测量过程 view的测量是从ViewRootImpl发起的,View需要重绘,都是发送请求给ViewRootImpl,然后他组织重绘在重绘的过程中 ...
- Android学习Scroller(五)——具体解释Scroller调用过程以及View的重绘
PS: 该篇博客已经deprecated,不再维护.详情请參见 站在源代码的肩膀上全解Scroller工作机制 http://blog.csdn.net/lfdfhl/article/detail ...
随机推荐
- 关于数据库管理系统DBMS--关系型数据库(MySQL/MariaDB)
数据库的结构(3种):层次,网状,关系型(用的最多): DBMS的三层模型: 视图层:面向最终用户: 逻辑层:面向程序员或DBA: 物理层:面向系统管理员: 关系型数据库管理系统——RDBMS: 主要 ...
- 基于flexbox纯css框架的解析
学CSS很好的一个方法大概是先用纯CSS来实现一个自己的框架,然后便可以在之后的使用中对一开始可能很粗糙的框架做细致的优化与改进,删除些冗余,添加些功能之类的. 当然,为了避免一开始写框架时候的时候手 ...
- openlayers4 入门开发系列之地图切换篇(附源码下载)
前言 openlayers4 官网的 api 文档介绍地址 openlayers4 api,里面详细的介绍 openlayers4 各个类的介绍,还有就是在线例子:openlayers4 官网在线例子 ...
- vue 使用 supermap iclient-classic
1. 2.在组件中: import "@supermap/iclient-classic/libs/SuperMap-8.1.1-16520"; import { MapVLaye ...
- Linux如何管理文档多租户
例题 同一群组microsoft下的两个账号justmine001和justmine002需要共同拥有目录/microsoft/eshop的开发权,以便进行协同工作,但是其他人不允许进入和查阅该目录. ...
- 聊聊Unity2018的LWRP和混合光照
0x00 前言 在这篇文章中,我们选择了过去几周Unity官方社区交流群以及UUG社区群中比较有代表性的几个问题,总结在这里和大家进行分享.主要涵盖了** Scripting.Assetsbundle ...
- 分布式架构原理解析,Java开发必修课
1. 分布式术语 1.1. 异常 服务器宕机 内存错误.服务器停电等都会导致服务器宕机,此时节点无法正常工作,称为不可用. 服务器宕机会导致节点失去所有内存信息,因此需要将内存信息保存到持久化介质上. ...
- Java实现发送手机验证码功能(短信+语音)
利用第三方平台可以实现发送手机短信验证码和语音验证码的功能,本文使用框架是struts2+spring+hibernate,现就action层给出核心代码功能. public class Verify ...
- javascript权威指南笔记[6-8]
1.三类对象,两类属性 2.原型链只有在查询的时候才会体现 3.对象属性访问 4.属性赋值 5.delete只是断开属性和宿主对象的关系,不会去操作属性中的属性 6.Object.ke() var m ...
- Linux 网络命令必知必会之 tcpdump,一份完整的抓包指南请查收!
目录 01 简介 02 tcpdump 命令选项 03 过滤器 04 常用操作 4.1 抓取某主机的数据包 4.2 抓取某端口的数据包 4.3 抓取某网络(网段)的数据包 4.4 抓取某协议的数据包 ...