onCreate中的savedInstanceState有何具体作用

在activity的生命周期中，只要离开了可见阶段，或者说失去了焦点，activity就很可能被进程终止了！，被KILL掉了，，这时候，就需要有种机制，能保存当时的状态，这就是savedInstanceState的作用。

当一个Activity在PAUSE时，被kill之前，它可以调用onSaveInstanceState()来保存当前activity的状态信息（在paused状态时，要被KILLED的时候）。用来保存状态信息的Bundle会同时传给两个method,即onRestoreInstanceState() and onCreate().

示例代码如下：

1. package com.myandroid.test;
2. import android.app.Activity;
3. import android.os.Bundle;
4. import android.util.Log;
5. public class AndroidTest extends Activity {
6. private static final String TAG = 'MyNewLog';
7. /** Called when the activity is first created. */
8. @Override
9. public void onCreate(Bundle savedInstanceState) {
10. super.onCreate(savedInstanceState);
11. // If an instance of this activity had previously stopped, we can
12. // get the original text it started with.
13. if(null != savedInstanceState)
14. {
15. int IntTest = savedInstanceState.getInt('IntTest');
16. String StrTest = savedInstanceState.getString('StrTest');
17. Log.e(TAG, 'onCreate get the savedInstanceState+IntTest='+IntTest+'+StrTest='+StrTest);
18. }
19. setContentView(R.layout.main);
20. Log.e(TAG, 'onCreate');
21. }
22. @Override
23. public void onSaveInstanceState(Bundle savedInstanceState) {
24. // Save away the original text, so we still have it if the activity
25. // needs to be killed while paused.
26. savedInstanceState.putInt('IntTest', 0);
27. savedInstanceState.putString('StrTest', 'savedInstanceState test');
28. super.onSaveInstanceState(savedInstanceState);
29. Log.e(TAG, 'onSaveInstanceState');
30. }
31. @Override
32. public void onRestoreInstanceState(Bundle savedInstanceState) {
33. super.onRestoreInstanceState(savedInstanceState);
34. int IntTest = savedInstanceState.getInt('IntTest');
35. String StrTest = savedInstanceState.getString('StrTest');
36. Log.e(TAG, 'onRestoreInstanceState+IntTest='+IntTest+'+StrTest='+StrTest);
37. }
38. }