Java Android onSaveInstanceState始终为空

考虑以下方法：

@Override
public void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    outState.putSerializable("repertoire",rep);
}

我正在使用Android Studio生成的菜单

NavigationDrawer

。当我回到主活动时，

savedInstanceState

在我的类中总是

null

：

公共类MainActivity扩展ActionBarActivity实现NavigationDrawerFragment.NavigationDrawerCallbacks：

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    if( savedInstanceState != null ) {
        rep = (repertoire) savedInstanceState.getSerializable("repertoire");
            }
        setContentView(R.layout.activity_main);

        mNavigationDrawerFragment = (NavigationDrawerFragment)                      getSupportFragmentManager().findFragmentById(R.id.navigation_drawer);
        mTitle = getTitle();
        ListView vue = (ListView) findViewById(R.id.listView);
        if(rep==null){
            rep = new repertoire();
        }

        // Set up the drawer.
        mNavigationDrawerFragment.setUp(
                R.id.navigation_drawer,
                (DrawerLayout) findViewById(R.id.drawer_layout));
}

---

我不是100%确定，但是您不应该在onRestoreInstanceState（）中还原您的活动吗？同样，我不是100%确定，但它可能会工作。

继续创建它

@Override
public void onSaveInstanceState(Bundle outState) {
    if (outState == null) {
        outState = new Bundle();
    }

    outState.putSerializable("repertoire", rep);

    super.onSaveInstanceState(outState);
}

超级方法不会做任何事情，除非将一个非null的

Bundle

传递给它，并且它的超级方法只是一个存根！视图层次将单独保存。现在，您将在

onCreate（Bundle）

和

onRestoreInstanceState（Bundle）

中以参数形式接收

Bundle
我的当前代码：
在onCreate中：

                  @Override
        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
              if( savedInstanceState != null ) {
                  System.out.println("back");
                  rep = (repertoire) savedInstanceState.getSerializable("repertoire");
              }

以及：

                @Override
        public void onSaveInstanceState(Bundle outState) {
            System.out.println("bibi");
            if (outState == null) {
                outState = new Bundle();
            }
            super.onSaveInstanceState(outState);
            outState.putSerializable("repertoire", rep);


        }
            @Override
            public void onRestoreInstanceState(Bundle bundle){
                System.out.println("okm");
                super.onRestoreInstanceState(bundle);
                bundle.putSerializable("repertoire",rep);
            }