Question

好的，我已经覆盖了OnSaveInstanceState和OnRestoreInstanceState，但在OnCreate中，bundle是null。我已经完成了所有其他相关问题，但它们并没有为我工作。这是我的主要活动。

public class MainActivity extends AppCompatActivity {
RecyclerView recyclerView;
List<Bundle> bundles;
Bundle bundle;
CustomAdapter customAdapter;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    if(savedInstanceState==null) {
        Log.i("abc3","savedInstanceState is null, called in OnCreate");
        bundle = new Bundle();
        bundle.putInt("productImage", R.drawable.happy);
        bundle.putString("nameOfProduct", "iPhone0");
        bundle.putString("productAmount", "5000");
        bundle.putString("nameOfDestination", "DGBDGHIDAFGK");
        bundle.putString("addressOfDestination", "Velachery Main Road, Near IIT Madras, Chennai,Tamil Nadu,India 600042");
        bundle.putString("contactno", "0123456789");
        bundle.putBoolean("isSeller", true);
        bundles = new ArrayList<>();
        bundles.add(0, bundle);
    /*Log.i("abc1", bundle.getString("nameOfProduct"));
    bundle.remove("nameOfProduct");
    bundle.putString("nameOfProduct", "iPhone1");*/
        Bundle bundle1 = new Bundle();
        bundle1.putInt("productImage", R.drawable.happy);
        bundle1.putString("nameOfProduct", "iPhone1");
        bundle1.putString("productAmount", "5000");
        bundle1.putString("nameOfDestination", "DGBDGHIDAFGK");
        bundle1.putString("addressOfDestination", "Velachery Main Road, Near IIT Madras, Chennai,Tamil Nadu,India 600042");
        bundle1.putString("contactno", "0123456789");
        bundle1.putBoolean("isSeller", true);
        bundles.add(1, bundle1);
    /*Log.i("abc1", bundle.getString("nameOfProduct"));
    bundle.remove("nameOfProduct");
    bundle.putString("nameOfProduct", "iPhone2");*/
        Bundle bundle2 = new Bundle();
        bundle2.putInt("productImage", R.drawable.happy);
        bundle2.putString("nameOfProduct", "iPhone2");
        bundle2.putString("productAmount", "5000");
        bundle2.putString("nameOfDestination", "DGBDGHIDAFGK");
        bundle2.putString("addressOfDestination", "Velachery Main Road, Near IIT Madras, Chennai,Tamil Nadu,India 600042");
        bundle2.putString("contactno", "0123456789");
        bundle2.putBoolean("isSeller", true);
        bundles.add(2, bundle2);
    }
    else
    {
        Log.i("abc3","savedInstanceState is not null,called in OnCreate");
        for(int i=0;savedInstanceState.containsKey(String.valueOf(i));++i)
            bundles.add(savedInstanceState.getBundle(String.valueOf(i)));

    }

    /*Log.i("abc1", bundle.getString("nameOfProduct"));*/
    recyclerView = (RecyclerView) findViewById(R.id.recycler_view);
    customAdapter= new CustomAdapter(this,bundles,recyclerView);
    RecyclerView.LayoutManager mLayoutManager = new LinearLayoutManager(getApplicationContext());
    recyclerView.setLayoutManager(mLayoutManager);
    recyclerView.setItemAnimator(new DefaultItemAnimator());
    recyclerView.setAdapter(customAdapter);
}
@Override
public void onSaveInstanceState(Bundle savedInstanceState) {

    bundles = customAdapter.getBundleList();
   // Log.i("abc3", String.valueOf(bundles.size()));
    for(int i=0;i<bundles.size();++i)
    {savedInstanceState.putBundle(String.valueOf(i),bundles.get(i));}
    super.onSaveInstanceState(savedInstanceState);
    if(savedInstanceState==null)Log.i("abc3","savedInstanceState is null, called in onSaveInstanceState");
    else Log.i("abc3","savedInstanceState is not null, called in onSaveInstanceState");
}
@Override
public void onRestoreInstanceState(Bundle savedInstanceState)
{
    if(savedInstanceState!=null)
        for(int i=0;savedInstanceState.containsKey(String.valueOf(i));++i)
            bundles.add(savedInstanceState.getBundle(String.valueOf(i)));
    super.onRestoreInstanceState(savedInstanceState);
}
}

和我的清单

<application
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:supportsRtl="true"
    android:theme="@style/Theme.AppCompat.Light.DarkActionBar">
    <activity android:name=".MainActivity">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
</application>

当我开始活动时，这是我的logcat，然后关闭它，然后再次启动它。

  06-05 12:56:46.777 27184-27184/com.example.sharath.delivery_app I/abc3: savedInstanceState is null, called in OnCreate
  06-05 12:56:53.384 27184-27184/com.example.sharath.delivery_app I/abc3: savedInstanceState is not null, called in onSaveInstanceState
  06-05 12:57:00.613 27443-27443/com.example.sharath.delivery_app I/abc3: savedInstanceState is null, called in OnCreate

我试过打电话

 super.onSaveInstanceState(savedInstanceState);

在方法的开头，而不是在结尾，但没有变化。

Answer 1

此行为看起来是正确的。你说你做的是：

我开始活动，然后关闭它，然后重新开始。

在这种情况下，Android不会恢复您的活动状态。当用户故意关闭活动时，所有状态都被丢弃，当他们稍后启动时，他们会得到一份新的副本。

仅在重新创建活动时恢复状态，因为它已被系统销毁，但用户不希望它被关闭，因此他们希望活动的状态相同。一种这样的情况是屏幕旋转（或通常任何配置改变）。

尽管调用了onSaveInstance，但在OnCreate中savedInstanceState始终为null

1 个答案: