Analysis of Launcher startup process in Android 11.0 framework

1 Introduction

  In the 11.0 system rom customization development, in the rom customization process, it is very important for the launcher startup process to develop the default Launcher function, solve the black screen after the boot animation, understand the fallbackhome mechanism, etc., and then analyze
it Launcher's startup process

2. The core class of the launch process analysis of the Launcher in the framework

frameworks/base/services/java/com/android/server/SystemServer.java
frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java
frameworks/base/services/core/java/com/android/server/wm/ActivityTaskManagerService.java

3. Core function analysis and implementation of the Launcher startup process analysis in the framework
3.1 Analyze the related methods of starting AMS in SystemServer.java

      private void run() {
          TimingsTraceAndSlog t = new TimingsTraceAndSlog();
          try {
              t.traceBegin("InitBeforeStartServices");
  
              // Record the process start information in sys props.
              SystemProperties.set(SYSPROP_START_COUNT, String.valueOf(mStartCount));
              SystemProperties.set(SYSPROP_S