savedInstanceState的作用

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：

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);
    }
}

原址：http://blog.csdn.net/wangjia55/article/details/8226568