2011-9-27 22:08:16-优快云博客

本文链接：https://blog.youkuaiyun.com/cstk502/article/details/6827928

本文详细解析了Android中ActivityManagerProxy的startActivity方法和ActivityManagerService的startActivity函数，深入探讨了Activity启动过程中的关键参数及其作用。

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2011-9-27 22:08:16

Step 5. ActivityManagerProxy.startActivity

这个函数定义在frameworks/base/core/java/android/app/ActivityManagerNative.java文件中：

class ActivityManagerProxy implements IActivityManager
{

......

public int startActivity(IApplicationThread caller, Intent intent,
   String resolvedType, Uri[] grantedUriPermissions, int grantedMode,
   IBinder resultTo, String resultWho,
   int requestCode, boolean onlyIfNeeded,
   boolean debug) throws RemoteException {
  Parcel data = Parcel.obtain();
  Parcel reply = Parcel.obtain();
  data.writeInterfaceToken(IActivityManager.descriptor);
  data.writeStrongBinder(caller != null ? caller.asBinder() : null);
  intent.writeToParcel(data, 0);
  data.writeString(resolvedType);
  data.writeTypedArray(grantedUriPermissions, 0);
  data.writeInt(grantedMode);
  data.writeStrongBinder(resultTo);
  data.writeString(resultWho);
  data.writeInt(requestCode);
  data.writeInt(onlyIfNeeded ? 1 : 0);
  data.writeInt(debug ? 1 : 0);
  mRemote.transact(START_ACTIVITY_TRANSACTION, data, reply, 0);
  reply.readException();
  int result = reply.readInt();
  reply.recycle();
  data.recycle();
  return result;
}

......

} 这里的参数比较多，我们先整理一下。从上面的调用可以知道，这里的参数resolvedType、grantedUriPermissions和resultWho均为null；

参数caller为ApplicationThread类型的Binder实体；参数resultTo为一个Binder实体的远程接口，我们先不关注它；
参数grantedMode为0，我们也先不关注它；参数requestCode为-1；参数onlyIfNeeded和debug均空false。

Step 6. ActivityManagerService.startActivity

        上一步Step 5通过Binder驱动程序就进入到ActivityManagerService的startActivity函数来了，

        它定义在frameworks/base/services/java/com/android/server/am/ActivityManagerService.java文件中：

public final class ActivityManagerService extends ActivityManagerNative
implements Watchdog.Monitor, BatteryStatsImpl.BatteryCallback {

......

public final int startActivity(IApplicationThread caller,
   Intent intent, String resolvedType, Uri[] grantedUriPermissions,
   int grantedMode, IBinder resultTo,
   String resultWho, int requestCode, boolean onlyIfNeeded,
   boolean debug) {
  return mMainStack.startActivityMayWait(caller, intent, resolvedType,
   grantedUriPermissions, grantedMode, resultTo, resultWho,
   requestCode, onlyIfNeeded, debug, null, null);
}

......

} 这里只是简单地将操作转发给成员变量mMainStack的startActivityMayWait函数，这里的mMainStack的类型为ActivityStack。