java - SavedInstanceState 为空

Question

我想在与另一台设备“同步”时获取当前系统时间。因此，此 Activity 通常在同步后立即调用/显示。

目前，当前系统时间是正确的，但我还弹出另一个 Activity 的警报，一旦我完成该 Activity ，我想返回到该 Activity 。一旦我这样做，系统时间将更新为最新时间，而不是旧的当前时间(这就是我想要的)。

我尝试使用SavedInstanceState来保存旧当前时间的状态，并且它确实在onSavedInstanceState中获取了正确的字符串。当我返回此 Activity 时，SavedInstanceState 为 null。我不知道为什么？

public class InfoActivity extends BaseActivity  {

String fileLastSync = null;

   @Override
   public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.info);
        Resources resources = context.getResources();

        if (savedInstanceState != null) {
           // Restore value of members from saved state
           fileLastSync = savedInstanceState.getString("FileLastSync");
       } else {
           //Gets the current DateTime
           long nextTime = (System.currentTimeMillis());
           Date date = new Date(nextTime);

           //Formats the current DateTime
           SimpleDateFormat format = new SimpleDateFormat("MM-dd-yyyy HH:mm a");
           String formatDate = format.format(date);

           //Last sync time is the current formatted date
           fileLastSync = formatDate;
       }

       //Gets the 'last synced' string and sets to datetime of the last sync
       String syncString = String.format(resources.getString(R.string.last_sync), fileLastSync);

       //Dynamically sets the datetime of the last sync string
       TextView lastSyncTextView = ((TextView) findViewById(R.id.last_sync) );
       lastSyncTextView.setText(syncString);
}

    @Override
    protected void onSaveInstanceState(Bundle savedInstanceState) {

        savedInstanceState.putString("FileLastSync",fileLastSync);
        super.onSaveInstanceState(savedInstanceState);
    }

 @Override
 protected void onRestoreInstanceState(Bundle savedInstanceState) {
    super.onRestoreInstanceState(savedInstanceState);
    if (savedInstanceState != null) {
        // Restore value of members from saved state
        fileLastSync = savedInstanceState.getString("FileLastSync");
    } else {
        //Gets the current DateTime
        long nextTime = (System.currentTimeMillis());
        Date date = new Date(nextTime);

        //Formats the current DateTime
        SimpleDateFormat format = new SimpleDateFormat("MM-dd-yyyy hh:mm a");
        String formatDate = format.format(date);

        //Last sync time is the current formatted date
        fileLastSync = formatDate;

    }

}

}

编辑:我尝试将以下内容: super.onSaveInstanceState(savedInstanceState); 放在方法的末尾，但仍然不起作用。

Answer 1

您不应将 onSave 中的相同代码放入 onRestore 中。将完整的 if 语句从 onCreate 方法复制到 onRestore 方法中。并调用 super.onRestoreInstanceState 作为第一条语句。

编辑:抱歉 - 本来是一条评论