onCreate中的savedInstanceState的作用

onCreate中的savedInstanceState的作用2010-11-28 17:23
（轉載自http://blog.csdn.net/xiaoxiao_job/archive/2010/08/31/5852811.aspx，感謝作者的智慧）

在activity的生命週期中，只要離開了可見階段，或者說失去了焦點，activity就很可能被進程終止了！，被KILL掉了，，這時候，就需要有種機制，能儲存當時的狀態，這就是savedInstanceState的作用。

當一個Activity在PAUSE時，被kill之前，它可以調用onSaveInstanceState()來儲存當前activity的狀態資訊（在paused狀態時，要被KILLED的時候）。用來儲存狀態資訊的Bundle會同時傳給兩個method,即onRestoreInstanceState() and onCreate().

範例程式碼如下：

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);