ActivityThread源码分析

分类：Android, Java 阅读 (1,908) Add comments

2月 222019

转载请注明原文地址：http://bcoder.com/java/analysis-of-activitythread

　　本文基于Android4.4版本源码进行分析。

　　一直以为ActivityThread是一个继承自Thread类的子线程，今天初看这个类发现里面的业务逻辑这么多，看了看网上的其他文章，原来这个Thread指的是Android应用的主线程啊。

问：安卓应用的入口函数是哪个？

答：~~Application.onCreate。错错错~~

正确的答案是ActivityThraed的main函数。

Android应用入口，ActivityThread.main　　

下面咱们就看看ActivityThread.main函数：

    public static void main(String[] args) {
        SamplingProfilerIntegration.start();

        // CloseGuard defaults to true and can be quite spammy.  We
        // disable it here, but selectively enable it later (via
        // StrictMode) on debug builds, but using DropBox, not logs.
        CloseGuard.setEnabled(false);

        Environment.initForCurrentUser();

        // Set the reporter for event logging in libcore
        EventLogger.setReporter(new EventLoggingReporter());

        Security.addProvider(new AndroidKeyStoreProvider());

        Process.setArgV0("<pre-initialized>");

        Looper.prepareMainLooper();

        ActivityThread thread = new ActivityThread();
        thread.attach(false);

        if (sMainThreadHandler == null) {
            sMainThreadHandler = thread.getHandler();
        }

        AsyncTask.init();

        if (false) {
            Looper.myLooper().setMessageLogging(new
                    LogPrinter(Log.DEBUG, "ActivityThread"));
        }

        Looper.loop();

        throw new RuntimeException("Main thread loop unexpectedly exited");
    }

public static void main(String[] args) {

SamplingProfilerIntegration.start();

// CloseGuard defaults to true and can be quite spammy. We

// disable it here, but selectively enable it later (via

// StrictMode) on debug builds, but using DropBox, not logs.

CloseGuard.setEnabled(false);

Environment.initForCurrentUser();

// Set the reporter for event logging in libcore

EventLogger.setReporter(new EventLoggingReporter());

Security.addProvider(new AndroidKeyStoreProvider());

Process.setArgV0("<pre-initialized>");

Looper.prepareMainLooper();

ActivityThread thread = new ActivityThread();

thread.attach(false);

if (sMainThreadHandler == null) {

sMainThreadHandler = thread.getHandler();

}

AsyncTask.init();

if (false) {

Looper.myLooper().setMessageLogging(new

LogPrinter(Log.DEBUG, "ActivityThread"));

}

Looper.loop();

throw new RuntimeException("Main thread loop unexpectedly exited");

}

♦	首先，第一步启动SamplingProfilerIntegration，这个封装类集成了Dalvik的性能分析工具，用于监测记录应用的性能参数？待进一步查看代码
	相关源码：./frameworks/base/core/java/com/android/internal/os/SamplingProfilerIntegration.java ./frameworks/base/services/java/com/android/server/SamplingProfilerService.java ./libcore/dalvik/src/main/java/dalvik/system/profiler/SamplingProfiler.java
♦	紧接着CloseGuard.setEnabled(false);
	CloseGuard类实现了一种机制用于检查是否有内存泄露，默认是关闭，可以通过setEnabled(true)开启。
	源码路径：libcore/dalvik/src/main/java/dalvik/system/CloseGuard.java
♦	Environment.initForCurrentUser();初始化Environment类，主要是一些目录的设置，比如我们通常用的获取外部存储路径函数Environment.getExternalStorageDirectory()的返回值就是在这里进行初始化的。
	源码路径：libcore/luni/src/main/java/libcore/io/EventLogger.java
♦	EventLogger.setReporter(new EventLoggingReporter());
	没看懂怎么用的
	相关源码：libcore/luni/src/main/java/libcore/io/EventLogger.java
♦	Security.addProvider(new AndroidKeyStoreProvider());
	为应用添加安全检测管理器，使用AndroidKeyStoreProvider，keystore就是指打release包时的数字证书吧
	相关源码：frameworks/base/keystore/java/android/security/AndroidKeyStoreProvider.java frameworks/base/keystore/java/android/security/AndroidKeyStore.java
♦	Process.setArgV0(“<pre-initialized>”);
	因为应用还未启动完成，先给进程设置一个名字为<pre-initialized>
	相关源码：frameworks/base/core/java/android/os/Process.java
♦	Looper.prepareMainLooper();
	将当前线程初始化为一个Looper，用Looper来管理线程内的各种请求。并将该Looper做为程序的主Looper。
	相关源码：frameworks/base/core/java/android/os/Looper.java
♦	ActivityThread thread = new ActivityThread(); thread.attach(false);


♦	AsyncTask.init();
	初始化AsyncTask，这是一个静态函数，由此可见AsyncTask的串行执行。
♦	if (false) { Looper.myLooper().setMessageLogging(new LogPrinter(Log.DEBUG, “ActivityThread”)); }

♦	Looper.loop();
	开始循环主线程里的MessageQueue

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Android应用入口，ActivityThread.main

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Android应用入口，ActivityThread.main　　