onCreate onRestoreInstanceState onSaveInstanceState

1.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。

2.在Activity里的onCreate(Bundle savedInstanceState)函数中，savedInstanceState这个参数是用来存储Activity的信息，包括了每个UI的信息和用户自定义在其中存储的信息。

3.

在activity被杀掉之前调用保存每个实例的状态,以保证该状态可以在onCreate(Bundle)或者onRestoreInstanceState(Bundle) (传入的Bundle参数是由onSaveInstanceState封装好的)中恢复。这个方法在一个activity被杀死前调用，当该activity在将来某个时刻回来时可以恢复其先前状态。例如，如果activity B启用后位于activity A的前端，在某个时刻activity A因为系统回收资源的问题要被杀掉，A通过onSaveInstanceState将有机会保存其用户界面状态，使得将来用户返回到activity A时能通过onCreate(Bundle)或者onRestoreInstanceState(Bundle)恢复界面的状态。

4.一个调用onPause()但不调用onSaveInstanceState的例子是当activity B启动并处在activity A的前端：如果在B的整个生命周期里A的用户界面状态都没有被破坏的话，系统是不会调用activity A的onSaveInstanceState(Bundle)的。

5.

package com.myandroid.test;

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;

public class AndroidTest extends Activity {
    private static final String TAG = "MyNewLog";
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        // If an instance of this activity had previously stopped, we can
        // get the original text it started with.
        if(null != savedInstanceState)
        {
            int IntTest = savedInstanceState.getInt("IntTest"); 
            String StrTest = savedInstanceState.getString("StrTest"); 
            Log.e(TAG, "onCreate get the savedInstanceState+IntTest="+IntTest+"+StrTest="+StrTest);  
        }

        setContentView(R.layout.main);
        Log.e(TAG, "onCreate");
    }

    @Override 
    public void onSaveInstanceState(Bundle savedInstanceState) { 
      // Save away the original text, so we still have it if the activity
      // needs to be killed while paused.
      savedInstanceState.putInt("IntTest", 0); 
      savedInstanceState.putString("StrTest", "savedInstanceState test"); 
      super.onSaveInstanceState(savedInstanceState); 
      Log.e(TAG, "onSaveInstanceState");
    } 

    @Override 
    public void onRestoreInstanceState(Bundle savedInstanceState) { 
      super.onRestoreInstanceState(savedInstanceState); 

      int IntTest = savedInstanceState.getInt("IntTest"); 

      String StrTest = savedInstanceState.getString("StrTest"); 

      Log.e(TAG, "onRestoreInstanceState+IntTest="+IntTest+"+StrTest="+StrTest);
    } 
}