管理Activity的生命周期（4）重建Activity

最新推荐文章于 2023-05-15 16:06:58 发布

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最新推荐文章于 2023-05-15 16:06:58 发布

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文章标签： Activity生命周期 Activity Android

本文链接：https://blog.youkuaiyun.com/yymonkeydo/article/details/42239343

本文详细介绍了在游戏开发中如何通过 onSaveInstanceState 和 onRestoreInstanceState 方法实现 Activity 的状态保存与恢复，确保用户游戏进度不受屏幕旋转的影响。

当用户旋转屏幕（如果程序允许横竖屏幕切换的话），我们的Activty将会被destroed并且会被重新创建。因为我们的app此时要重新加载不同的资源文件。

保存Activity的状态

static final String STATE_SCORE = "playerScore";
static final String STATE_LEVEL = "playerLevel";
...

@Override
public void onSaveInstanceState(Bundle savedInstanceState) {
    // Save the user's current game state
    savedInstanceState.putInt(STATE_SCORE, mCurrentScore);
    savedInstanceState.putInt(STATE_LEVEL, mCurrentLevel);
    
    // Always call the superclass so it can save the view hierarchy state
    super.onSaveInstanceState(savedInstanceState);
}

恢复Activity状态

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState); // Always call the superclass first
   
    // Check whether we're recreating a previously destroyed instance
    if (savedInstanceState != null) {
        // Restore value of members from saved state
        mCurrentScore = savedInstanceState.getInt(STATE_SCORE);
        mCurrentLevel = savedInstanceState.getInt(STATE_LEVEL);
    } else {
        // Probably initialize members with default values for a new instance
    }
    ...
}

在onCreate()中恢复状态，需要判断Bundle是不是空的，不过，如果用onRestoreInstanceState()的话（在onStart()方法之后被调用），就不用判断Bundle是不是空的，因为这个方法，只有在有保存状态的时候，它才会被调用的。

public void onRestoreInstanceState(Bundle savedInstanceState) {
    // Always call the superclass so it can restore the view hierarchy
    super.onRestoreInstanceState(savedInstanceState);
   
    // Restore state members from saved instance
    mCurrentScore = savedInstanceState.getInt(STATE_SCORE);
    mCurrentLevel = savedInstanceState.getInt(STATE_LEVEL);
}