关于activity中onCreate方法的bundle参数

/**

• @author ChenYe
• 直接看代码和注释吧 */

public class MainActivity extends AppCompatActivity {
 
    private static final String TAG = "cy===MainActivity";
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
 
        /**
         * savedInstanceState的作用是，当activity被系统回收的时候会调用 onSaveInstate(Bundle savedInstanceState)来保存东西，
         * 那么下一次启动这个Activity的时候会在onCreate的时候保存的东西再传递进来。比如横竖屏切换的时候，会重新走这个onCreate，
         * 如果你在onSaveInstanceState里面存数据的话就可以拿到
         */
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        if (savedInstanceState != null) {
            String date = (String) savedInstanceState.get("date_test");
            Log.i(TAG, "日期:" + date);
        }
    }
 
    @Override
    protected void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);
        outState.putString("date_test", "2017-10-31");
    }
}