onCreate中的savedInstanceState的作用

最新推荐文章于 2025-02-26 16:33:16 发布

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本文解析了Android中Activity生命周期内的onCreate方法中savedInstanceState参数的作用。通过实例演示了如何在onSaveInstanceState方法中保存状态，并在onCreate及onRestoreInstanceState方法中恢复状态，确保了在Activity被销毁重建时仍能保持原有状态。

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onCreate中的savedInstanceState的作用2010-11-28 17:23 （转载自http://blog.youkuaiyun.com/xiaoxiao_job/archive/2010/08/31/5852811.aspx，感谢作者的智慧）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);