Android知识总结
一、Activity的启动过程
ActivityManagerService：activity的启动以及生命周期都统一由ActivityManagerService管理，而ActivityManagerService处于SystemServer进程中，应用程序进程通过Binder机制与SystemServer进程进行通信。ActivityManagerProxy：是ActivityManagerService在客户端的代理，客户端通过ActivityManageProxy间接调用ActivityManagerService。ActivityThread：应用程序的主线程ActivityThread，也是应用程序的入口；消息循环机制的创建、初始化信息等都在ActivityThread中完成。ApplicationThread：用来实现ActivityManagerService与ActivityThread之间的交互。在ActivityManagerService需要管理相关Application中的Activity的生命周期时，通过ApplicationThread的代理对象与ActivityThread通讯。ApplicationThreadProxy：是ApplicationThread在服务器端的代理，负责和客户端的ApplicationThread通讯。AMS就是通过该代理与ActivityThread进行通信的。Instrumentation：每一个应用程序只有一个Instrumentation对象，每个Activity内都有一个对该对象的引用。Instrumentation可以理解为应用进程的管家，ActivityThread要创建或暂停某个Activity时，都需要通过Instrumentation来进行具体的操作。
1.1、Launcher请求AMS阶段
1.2、AMS到ApplicationThread阶段
1.3、ApplicationThread到Activity阶段
二、判断Activity是否注册
在哪儿判断Activity是否在AndroidManifest.xml里面注册的？
首先没有在AndroidManifest.xml注册，报错是什么样子的
- 我们看
Instrumentation的execStartActivity方法
public ActivityResult execStartActivity(
Context who, IBinder contextThread, IBinder token, String target,
Intent intent, int requestCode, Bundle options) {
IApplicationThread whoThread = (IApplicationThread) contextThread;
if (mActivityMonitors != null) {
synchronized (mSync) {
final int N = mActivityMonitors.size();
for (int i=0; i= 0 ? am.getResult() : null;
}
break;
}
}
}
}
try {
intent.migrateExtraStreamToClipData(who);
intent.prepareToLeaveProcess(who);
//1.通过IActivityManager调用我们执行AMS的startActivity方法，并返回执行结果
int result = ActivityTaskManager.getService().startActivity(whoThread,
who.getBasePackageName(), who.getAttributionTag(), intent,
intent.resolveTypeIfNeeded(who.getContentResolver()), token, target,
requestCode, 0, null, options);
//2. 检查结果
checkStartActivityResult(result, intent);
} catch (RemoteException e) {
throw new RuntimeException("Failure from system", e);
}
return null;
}
接下来看checkStartActivityResult方法
public static void checkStartActivityResult(int res, Object intent) {
if (!ActivityManager.isStartResultFatalError(res)) {
return;
}
switch (res) {
case ActivityManager.START_INTENT_NOT_RESOLVED:
case ActivityManager.START_CLASS_NOT_FOUND:
//3. 这里我们找到了报错的地方，原来是res结果为START_INTENT_NOT_RESOLVED，
//START_CLASS_NOT_FOUND就会报这个错误
if (intent instanceof Intent && ((Intent)intent).getComponent() != null)
throw new ActivityNotFoundException(
"Unable to find explicit activity class "
+ ((Intent)intent).getComponent().toShortString()
+ "; have you declared this activity in your AndroidManifest.xml?");
throw new ActivityNotFoundException(
"No Activity found to handle " + intent);
case ActivityManager.START_PERMISSION_DENIED:
throw new SecurityException("Not allowed to start activity "
+ intent);
case ActivityManager.START_FORWARD_AND_REQUEST_CONFLICT:
throw new AndroidRuntimeException(
"FORWARD_RESULT_FLAG used while also requesting a result");
case ActivityManager.START_NOT_ACTIVITY:
throw new IllegalArgumentException(
"PendingIntent is not an activity");
case ActivityManager.START_NOT_VOICE_COMPATIBLE:
throw new SecurityException(
"Starting under voice control not allowed for: " + intent);
case ActivityManager.START_VOICE_NOT_ACTIVE_SESSION:
throw new IllegalStateException(
"Session calling startVoiceActivity does not match active session");
case ActivityManager.START_VOICE_HIDDEN_SESSION:
throw new IllegalStateException(
"Cannot start voice activity on a hidden session");
case ActivityManager.START_ASSISTANT_NOT_ACTIVE_SESSION:
throw new IllegalStateException(
"Session calling startAssistantActivity does not match active session");
case ActivityManager.START_ASSISTANT_HIDDEN_SESSION:
throw new IllegalStateException(
"Cannot start assistant activity on a hidden session");
case ActivityManager.START_CANCELED:
throw new AndroidRuntimeException("Activity could not be started for "
+ intent);
default:
throw new AndroidRuntimeException("Unknown error code "
+ res + " when starting " + intent);
}
}
private final void validateNotAppThread() {
if (Looper.myLooper() == Looper.getMainLooper()) {
throw new RuntimeException(
"This method can not be called from the main application thread");
}
}