Framework 窗口添加流程分析1之 ViewRootImpl 创建_viewrootimpl绘制流程-优快云博客

本文链接：https://blog.youkuaiyun.com/wg_mlo/article/details/127358229

本文详细剖析了Android中Activity窗口添加的过程，从ActivityThread的handleResumeActivity开始，经过performResumeActivity、makeVisible等步骤，重点讲解了ViewRootImpl的创建和View的绘制流程，涉及到WindowManagerImpl、WindowManagerGlobal以及WMS的交互。文章为理解Android应用程序界面显示的底层机制提供了深入见解。

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Framework 窗口添加流程分析1之 ViewRootImpl 创建

ActivityThread.handleResumeActivity()

// 第一部分析: 执行resumed流程，回调 Activity.onResume()

-> ActivityThread.performResumeActivity()

-> Activity.performResume()

-> Activity.dispatchActivityPreResumed()

-> Instrumentation.callActivityOnResume()

-> Activity.onResume()

-> FragmentController.dispatchResume()

-> Activity.dispatchActivityPostResumed()

-> ActivityThread.reportTopResumedActivityChanged()

// 第二部分析: 添加窗口，绘制应用界面，使 activity 可见

-> Activity.makeVisible()

-> WindowManagerImpl.addView()

-> WindowManagerGlobal.addView()

-> new ViewRootImpl()

-> DecorView.setLayoutParams()

-> ViewRootImpl.setView()

// 第三部分析: View 的绘制

-> ViewRootImpl.requestLayout()

-> checkThread() // 检查线程是不是创建 ViewRootImpl 的原始线程(可以大概理解为主线程)

-> mLayoutRequested = true

-> scheduleTraversals()

-> mHandler.getLooper().getQueue().postSyncBarrier()

-> mChoreographer.postCallback(Choreographer.CALLBACK_TRAVERSAL, mTraversalRunnable)

-> mHandler.getLooper().getQueue().removeSyncBarrier(mTraversalBarrier);

-> performTraversals()

-> performMeasure()

-> performLayout()

-> performDraw()

-> Session.addToDisplayAsUser() // Binder call

-> WMS.addWindow()

-> DecorView.setVisibility()

// frameworks/base/core/java/android/app/ActivityThread.java
@Override
public void handleResumeActivity(IBinder token, boolean finalStateRequest, boolean isForward,String reason) {
   
   
    // 省略部分
    // 这里会执行resumed相关流程，同时会回调 Activity.onResume()
    final ActivityClientRecord r = performResumeActivity(token, finalStateRequest, reason);
    if (r == null) {
   
   
        // We didn't actually resume the activity, so skipping any follow-up actions.
        return;
    }
    final Activity a = r.activity;

    if (!r.activity.mFinished && willBeVisible && r.activity.mDecor != null && !r.hideForNow) {
   
   
        // 省略部分
        r.activity.mVisibleFromServer = true;
        mNumVisibleActivities++;
        if (r.activity.mVisibleFromClient) {
   
   
            // 添加窗口，绘制应用界面，使 activity 可见
            r.activity.