onCreate()和onCreateView()调用的不仅仅是需要的(片段)

Question

有人可以解释为什么onCreate()和onCreateView()被调用的次数会随着每个方向的变化而增加吗？

这是一个非常简单的应用程序,由一个Activity由两个组成Fragments.第二个动态Fragment加载.如果您定义这两个中就不会有这样的行为.Fragmentsmain.xml

这是main.xml:

       <fragment class="ets.saeref.Left"
        android:id="@+id/left_frag"
        android:layout_weight="70"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>

     <FrameLayout android:id="@+id/right_frag" 
        android:layout_weight="30"
        android:layout_width="match_parent" 
        android:layout_height="match_parent"/>

</LinearLayout>

这里留下了碎片:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="match_parent" android:background="#000000">
    <Button android:text="Landscape" android:id="@+id/button1"
        android:layout_width="wrap_content" android:layout_height="wrap_content"></Button>

</LinearLayout>

这是正确的碎片:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="match_parent" android:background="#ffffff">
    <Button android:text="Landscape" android:id="@+id/button1"
        android:layout_width="wrap_content" android:layout_height="wrap_content"></Button>

</LinearLayout>

Left.class:

public class Left extends Fragment {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Log.i("Left", "onCreate()");
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        Log.i("Left", "onCreateView()");
        return inflater.inflate(R.layout.left, container, false);
    }
}

Right.class:

public class Right extends Fragment {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Log.i("Right", "onCreate()");
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        Log.i("Right", "onCreateView()");
        return inflater.inflate(R.layout.right, container, false);
    }
}

主要课程:

public class Main extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        Fragment fg = new Right();
        getFragmentManager().beginTransaction().add(R.id.right_frag, fg)
            .commit();
        Log.i("Main", "onCreate()");
    }
}

几次方向更改后记录:

08-28 21:47:38.220: INFO/Main(1099): onCreate()
08-28 21:47:38.220: INFO/Right(1099): onCreateView()
08-28 21:47:38.220: INFO/Right(1099): onCreateView()
08-28 21:47:38.220: INFO/Right(1099): onCreateView()
08-28 21:47:38.220: INFO/Right(1099): onCreate()
08-28 21:47:38.220: INFO/Right(1099): onCreateView()
08-28 21:47:41.110: INFO/ActivityManager(142): Config changed: {1.0 0mcc0mnc en_US sw800dp w1280dp h752dp xlrg land finger -keyb/v/h -nav/h s.162}
08-28 21:47:41.140: INFO/Right(1099): onCreate()
08-28 21:47:41.140: INFO/Right(1099): onCreate()
08-28 21:47:41.140: INFO/Right(1099): onCreate()
08-28 21:47:41.140: INFO/Right(1099): onCreate()
08-28 21:47:41.170: INFO/Left(1099): onCreate()
08-28 21:47:41.170: INFO/Left(1099): onCreateView()
08-28 21:47:41.170: INFO/Main(1099): onCreate()
08-28 21:47:41.170: INFO/Right(1099): onCreateView()
08-28 21:47:41.170: INFO/Right(1099): onCreateView()
08-28 21:47:41.170: INFO/Right(1099): onCreateView()
08-28 21:47:41.170: INFO/Right(1099): onCreateView()
08-28 21:47:41.190: INFO/Right(1099): onCreate()
08-28 21:47:41.190: INFO/Right(1099): onCreateView()
08-28 21:47:45.070: INFO/ActivityManager(142): Config changed: {1.0 0mcc0mnc en_US sw800dp w800dp h1232dp xlrg port finger -keyb/v/h -nav/h s.163}
08-28 21:47:45.120: INFO/Right(1099): onCreate()
08-28 21:47:45.120: INFO/Right(1099): onCreate()
08-28 21:47:45.120: INFO/Right(1099): onCreate()
08-28 21:47:45.120: INFO/Right(1099): onCreate()
08-28 21:47:45.120: INFO/Right(1099): onCreate()
08-28 21:47:45.130: INFO/Left(1099): onCreate()
08-28 21:47:45.130: INFO/Left(1099): onCreateView()
08-28 21:47:45.130: INFO/Main(1099): onCreate()
08-28 21:47:45.130: INFO/Right(1099): onCreateView()
08-28 21:47:45.130: INFO/Right(1099): onCreateView()
08-28 21:47:45.130: INFO/Right(1099): onCreateView()
08-28 21:47:45.140: INFO/Right(1099): onCreateView()
08-28 21:47:45.140: INFO/Right(1099): onCreateView()
08-28 21:47:45.140: INFO/Right(1099): onCreate()
08-28 21:47:45.140: INFO/Right(1099): onCreateView()

Answer 1

我不能指向解释这一点的文档,但解决方案是仅在活动首次加载时创建和添加片段,如下所示:

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    if (savedInstanceState == null) {
        Fragment fg = new Right();
        getFragmentManager().beginTransaction().add(R.id.right_frag, fg)
            .commit();
    }
    Log.i("Main", "onCreate()");
}

Answer 2

是的,这是非常糟糕的记录.的解释是,当Activity是restored它会"自动神奇" restore的Fragments在里面添加的,所以adding另一个Fragment在你Activity基本上都会添加其他新Fragment上一顶部Fragment\s是实际restored的Android.

这种行为绝对是有意的,@ Joris Wit建议的方法是正确的.

当你考虑它时,这也是非常有用的,因为假设你有一堆叠加Fragments在一起,你可以使用back密钥导航回它们.在轮换的情况下,如果Android不能恢复Fragments你的后躯将失去所有这些,或者你将不得不实施一些机制来跟踪你的Fragment stack.

Answer 3

如果您不对不同的方向使用不同的布局,我认为您应该android:configChanges="orientation"在清单中使用. http://developer.android.com/guide/topics/manifest/activity-element.html#config