Android Launcher 會onCreate 兩次的原因

1. com.Android.server.am.ActivityStack
2. /**
3. * Make sure the given activity matches the current configuration. Returns
4. * false if the activity had to be destroyed. Returns true if the
5. * configuration is the same, or the activity will remain running as-is
6. * for whatever reason. Ensures the HistoryRecord is updated with the
7. * correct configuration and all other bookkeeping is handled.
8. */
9. final boolean ensureActivityConfigurationLocked(ActivityRecord r,
10. int globalChanges) {
11. ...
12. if ((changes&(~r.info.configChanges)) != 0) {
13. // Aha, the activity isn't handling the change, so DIE DIE DIE.
14. r.configChangeFlags |= changes;
15. r.startFreezingScreenLocked(r.app, globalChanges);
16. if (r.app == null || r.app.thread == null) {
17. if (DEBUG_SWITCH || DEBUG_CONFIGURATION) Slog.v(TAG,
18. "Switch is destroying non-running " + r);
19. destroyActivityLocked(r, true);
20. } else if (r.state == ActivityState.PAUSING) {
21. // A little annoying: we are waiting for this activity to
22. // finish pausing. Let's not do anything now, but just
23. // flag that it needs to be restarted when done pausing.
24. if (DEBUG_SWITCH || DEBUG_CONFIGURATION) Slog.v(TAG,
25. "Switch is skipping already pausing " + r);
26. r.configDestroy = true;
27. return true;
28. } else if (r.state == ActivityState.RESUMED) {
29. // Try to optimize this case: the configuration is changing
30. // and we need to restart the top, resumed activity.
31. // Instead of doing the normal handshaking, just say
32. // "restart!".
33. if (DEBUG_SWITCH || DEBUG_CONFIGURATION) Slog.v(TAG,
34. "Switch is restarting resumed " + r);
36. relaunchActivityLocked(r, r.configChangeFlags, true);
37. r.configChangeFlags = 0;
38. } else {
39. if (DEBUG_SWITCH || DEBUG_CONFIGURATION) Slog.v(TAG,
40. "Switch is restarting non-resumed " + r);
41. relaunchActivityLocked(r, r.configChangeFlags, false);
42. r.configChangeFlags = 0;
43. }
45. // All done... tell the caller we weren't able to keep this
46. // activity around.
47. return false;
48. }
49. ...
50. }

Why：

系統啟動後，搜索到可用移動網絡會觸發 config changes : mcc | mnc

“mcc“ The IMSI mobile country code (MCC) has changed — that is, a SIM hasbeen detected and updated the MCC.移動國家號碼，由三位數字組成，每個國家都有自己獨立的MCC，可以識別手機用戶所屬國家。
“mnc“ The IMSI mobile network code (MNC) has changed — that is, a SIM hasbeen detected and updated the MNC.移動網號，在一個國家或者地區中，用於區分手機用戶的服務商。

HowTo：

<activity android:name="Launcher" android:launchMode="singleTask" android:configChanges="mcc|mnc|keyboardHidden|orientation">