当前位置：文江博客话题详情

Android Fragment 生命周期随方向变化的变化

发布于 2024-12-20 13:20:59 字数 4237 浏览 4 评论 0原文

使用 Fragments 使用兼容包来面向 2.2。

在重新编码活动以在应用程序中使用片段后，我无法使方向更改/状态管理工作，因此我创建了一个带有单个 FragmentActivity 和单个 Fragment 的小型测试应用程序。

方向变化的日志很奇怪，多次调用片段 OnCreateView。

我显然错过了一些东西 - 比如分离片段并重新附加它而不是创建一个新实例，但我看不到任何文档来表明我出错的地方。

任何人都可以阐明我在这里做错了什么吗？谢谢

方向改变后日志如下。

Initial creation
12-04 11:57:15.808: D/FragmentTest.FragmentTestActivity(3143): onCreate
12-04 11:57:15.945: D/FragmentTest.FragmentOne(3143): OnCreateView
12-04 11:57:16.081: D/FragmentTest.FragmentOne(3143): OnCreateView->SavedInstanceState null


Orientation Change 1
12-04 11:57:39.031: D/FragmentTest.FragmentOne(3143): onSaveInstanceState
12-04 11:57:39.031: D/FragmentTest.FragmentTestActivity(3143): onCreate
12-04 11:57:39.031: D/FragmentTest.FragmentOne(3143): OnCreateView
12-04 11:57:39.031: D/FragmentTest.FragmentOne(3143): OnCreateView->SavedInstanceState not null
12-04 11:57:39.031: D/FragmentTest.FragmentOne(3143): OnCreateView
12-04 11:57:39.167: D/FragmentTest.FragmentOne(3143): OnCreateView->SavedInstanceState null


Orientation Change 2
12-04 11:58:32.162: D/FragmentTest.FragmentOne(3143): onSaveInstanceState
12-04 11:58:32.162: D/FragmentTest.FragmentOne(3143): onSaveInstanceState
12-04 11:58:32.361: D/FragmentTest.FragmentTestActivity(3143): onCreate
12-04 11:58:32.361: D/FragmentTest.FragmentOne(3143): OnCreateView
12-04 11:58:32.361: D/FragmentTest.FragmentOne(3143): OnCreateView->SavedInstanceState not null
12-04 11:58:32.361: D/FragmentTest.FragmentOne(3143): OnCreateView
12-04 11:58:32.361: D/FragmentTest.FragmentOne(3143): OnCreateView->SavedInstanceState not null
12-04 11:58:32.498: D/FragmentTest.FragmentOne(3143): OnCreateView
12-04 11:58:32.498: D/FragmentTest.FragmentOne(3143): OnCreateView->SavedInstanceState null

主Activity（FragmentActivity）

public class FragmentTestActivity extends FragmentActivity {
/** Called when the activity is first created. */

private static final String TAG = "FragmentTest.FragmentTestActivity";


FragmentManager mFragmentManager;

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

    Log.d(TAG, "onCreate");

    mFragmentManager = getSupportFragmentManager();
    FragmentTransaction fragmentTransaction = mFragmentManager.beginTransaction();

    FragmentOne fragment = new FragmentOne();

    fragmentTransaction.add(R.id.fragment_container, fragment);
    fragmentTransaction.commit();
}

和fragment

public class FragmentOne extends Fragment {

private static final String TAG = "FragmentTest.FragmentOne";

EditText mEditText;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {

    Log.d(TAG, "OnCreateView");

    View v = inflater.inflate(R.layout.fragmentonelayout, container, false);

    // Retrieve the text editor, and restore the last saved state if needed.
    mEditText = (EditText)v.findViewById(R.id.editText1);

    if (savedInstanceState != null) {

        Log.d(TAG, "OnCreateView->SavedInstanceState not null");

        mEditText.setText(savedInstanceState.getCharSequence("text"));
    }
    else {
        Log.d(TAG,"OnCreateView->SavedInstanceState null");
    }
    return v;
}

@Override
public void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);

    Log.d(TAG, "FragmentOne.onSaveInstanceState");

    // Remember the current text, to restore if we later restart.
    outState.putCharSequence("text", mEditText.getText());
}

Manifest

<uses-sdk android:minSdkVersion="8" />

<application
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name" >
    <activity
        android:label="@string/app_name"
        android:name=".activities.FragmentTestActivity" 
        android:configChanges="orientation">
        <intent-filter >
            <action android:name="android.intent.action.MAIN" />

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

原文

Using the compatibility package to target 2.2 using Fragments.

After recoding an activity to use fragments in an app I could not get the orientation changes/state management working so I've created a small test app with a single FragmentActivity and a single Fragment.

The logs from the orientation changes are weird, with multiple calls to the fragments OnCreateView.

I'm obviously missing something - like detatching the fragment and reattaching it rather than creating a new instance, but I can't see any documentation which would indicate where I'm going wrong.

Can anyone shed some light on what I'm doing wrong here please.
Thanks

The log is as follows after orientation changes.

Initial creation
12-04 11:57:15.808: D/FragmentTest.FragmentTestActivity(3143): onCreate
12-04 11:57:15.945: D/FragmentTest.FragmentOne(3143): OnCreateView
12-04 11:57:16.081: D/FragmentTest.FragmentOne(3143): OnCreateView->SavedInstanceState null


Orientation Change 1
12-04 11:57:39.031: D/FragmentTest.FragmentOne(3143): onSaveInstanceState
12-04 11:57:39.031: D/FragmentTest.FragmentTestActivity(3143): onCreate
12-04 11:57:39.031: D/FragmentTest.FragmentOne(3143): OnCreateView
12-04 11:57:39.031: D/FragmentTest.FragmentOne(3143): OnCreateView->SavedInstanceState not null
12-04 11:57:39.031: D/FragmentTest.FragmentOne(3143): OnCreateView
12-04 11:57:39.167: D/FragmentTest.FragmentOne(3143): OnCreateView->SavedInstanceState null


Orientation Change 2
12-04 11:58:32.162: D/FragmentTest.FragmentOne(3143): onSaveInstanceState
12-04 11:58:32.162: D/FragmentTest.FragmentOne(3143): onSaveInstanceState
12-04 11:58:32.361: D/FragmentTest.FragmentTestActivity(3143): onCreate
12-04 11:58:32.361: D/FragmentTest.FragmentOne(3143): OnCreateView
12-04 11:58:32.361: D/FragmentTest.FragmentOne(3143): OnCreateView->SavedInstanceState not null
12-04 11:58:32.361: D/FragmentTest.FragmentOne(3143): OnCreateView
12-04 11:58:32.361: D/FragmentTest.FragmentOne(3143): OnCreateView->SavedInstanceState not null
12-04 11:58:32.498: D/FragmentTest.FragmentOne(3143): OnCreateView
12-04 11:58:32.498: D/FragmentTest.FragmentOne(3143): OnCreateView->SavedInstanceState null

Main Activity (FragmentActivity)

public class FragmentTestActivity extends FragmentActivity {
/** Called when the activity is first created. */

private static final String TAG = "FragmentTest.FragmentTestActivity";


FragmentManager mFragmentManager;

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

    Log.d(TAG, "onCreate");

    mFragmentManager = getSupportFragmentManager();
    FragmentTransaction fragmentTransaction = mFragmentManager.beginTransaction();

    FragmentOne fragment = new FragmentOne();

    fragmentTransaction.add(R.id.fragment_container, fragment);
    fragmentTransaction.commit();
}

And the fragment

public class FragmentOne extends Fragment {

private static final String TAG = "FragmentTest.FragmentOne";

EditText mEditText;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {

    Log.d(TAG, "OnCreateView");

    View v = inflater.inflate(R.layout.fragmentonelayout, container, false);

    // Retrieve the text editor, and restore the last saved state if needed.
    mEditText = (EditText)v.findViewById(R.id.editText1);

    if (savedInstanceState != null) {

        Log.d(TAG, "OnCreateView->SavedInstanceState not null");

        mEditText.setText(savedInstanceState.getCharSequence("text"));
    }
    else {
        Log.d(TAG,"OnCreateView->SavedInstanceState null");
    }
    return v;
}

@Override
public void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);

    Log.d(TAG, "FragmentOne.onSaveInstanceState");

    // Remember the current text, to restore if we later restart.
    outState.putCharSequence("text", mEditText.getText());
}

Manifest

<uses-sdk android:minSdkVersion="8" />

<application
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name" >
    <activity
        android:label="@string/app_name"
        android:name=".activities.FragmentTestActivity" 
        android:configChanges="orientation">
        <intent-filter >
            <action android:name="android.intent.action.MAIN" />

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

分享到QQ

分享到微博

如果你对这篇内容有疑问，欢迎到本站社区发帖提问参与讨论，获取更多帮助，或者扫码二维码加入 Web 技术交流群。

发布评论

需要登录才能够评论，你可以免费注册一个本站的账号。

梦明 2024-12-27 13:20:59

您将 Fragments 一层一层地放在另一层之上。

当配置发生更改时，旧的 Fragment 会在重新创建时将其自身添加到新的 Activity 中。大多数时候，这是背部的巨大疼痛。

您可以通过使用相同的片段来阻止错误发生，而不是重新创建一个新的片段。只需添加此代码：

if (savedInstanceState == null) {
    // only create fragment if activity is started for the first time
    mFragmentManager = getSupportFragmentManager();
    FragmentTransaction fragmentTransaction = mFragmentManager.beginTransaction();

    FragmentOne fragment = new FragmentOne();

    fragmentTransaction.add(R.id.fragment_container, fragment);
    fragmentTransaction.commit();
} else {        
    // do nothing - fragment is recreated automatically
}

但请注意：如果您尝试从片段内部访问活动视图，则会出现问题，因为生命周期会发生微妙的变化。（从片段的父 Activity 获取视图并不容易）。

You're layering your Fragments one on top of the other.

When a config change occurs the old Fragment adds itself to the new Activity when it's recreated. This is a massive pain in the rear most of the time.

You can stop errors occurring by using the same Fragment rather than recreating a new one. Simply add this code:

if (savedInstanceState == null) {
    // only create fragment if activity is started for the first time
    mFragmentManager = getSupportFragmentManager();
    FragmentTransaction fragmentTransaction = mFragmentManager.beginTransaction();

    FragmentOne fragment = new FragmentOne();

    fragmentTransaction.add(R.id.fragment_container, fragment);
    fragmentTransaction.commit();
} else {        
    // do nothing - fragment is recreated automatically
}

Be warned though: problems will occur if you try and access Activity Views from inside the Fragment as the lifecycles will subtly change. (Getting Views from a parent Activity from a Fragment isn't easy).

回复收藏 0 原文

梦冥 2024-12-27 13:20:59

引用这本书，“以确保
一致的用户体验，Android 在发生错误时保留 Fragment 布局和关联的返回堆栈
由于配置更改，Activity 重新启动。”（第 124 页）

解决该问题的方法是首先检查 Fragment 返回堆栈是否已填充，仅当尚未填充时才创建新的 Fragment 实例：

@Override
public void onCreate(Bundle savedInstanceState) {

        ...    

    FragmentOne fragment = (FragmentOne) mFragmentManager.findFragmentById(R.id.fragment_container); 

    if (fragment == null) {
        FragmentTransaction fragmentTransaction = mFragmentManager.beginTransaction();
        fragmentTransaction.add(R.id.fragment_container, new FragmentOne());
        fragmentTransaction.commit();
    }
}

To cite this book, "to ensure a
consistent user experience, Android persists the Fragment layout and associated back stack when an
Activity is restarted due to a configuration change." (p. 124)

And the way to approach that is to first check if the Fragment back stack has already been populated, and create the new fragment instance only if it hasn't:

@Override
public void onCreate(Bundle savedInstanceState) {

        ...    

    FragmentOne fragment = (FragmentOne) mFragmentManager.findFragmentById(R.id.fragment_container); 

    if (fragment == null) {
        FragmentTransaction fragmentTransaction = mFragmentManager.beginTransaction();
        fragmentTransaction.add(R.id.fragment_container, new FragmentOne());
        fragmentTransaction.commit();
    }
}

回复收藏 0 原文

故人如初 2024-12-27 13:20:59

如您所见，您的活动的 onCreate() 方法在方向更改后被调用。因此，不要在 Activity 中方向更改后执行添加 Fragment 的 FragmentTransaction。

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    if (savedInstanceState==null) {
        //do your stuff
    }
}

片段应该并且必须保持不变。

The onCreate() method of your activity is called after the orientation change as you have seen. So, do not execute the FragmentTransaction that adds the Fragment after the orientation change in your activity.

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    if (savedInstanceState==null) {
        //do your stuff
    }
}

The Fragments should and must be unchanged.

回复收藏 0 原文

半暖夏伤 2024-12-27 13:20:59

您可以使用onSaveInstanceState()@Override FragmentActivity。请务必不要在该方法中调用super.onSaveInstanceState()。

回复收藏 0 原文

浅听莫相离 2024-12-27 13:20:59

我们应该始终尝试防止空指针异常，因此我们必须首先在 saveinstance 方法中检查包信息。有关简要说明，请查看此博客链接

public static class DetailsActivity extends Activity {

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

        if (getResources().getConfiguration().orientation
            == Configuration.ORIENTATION_LANDSCAPE) {
            // If the screen is now in landscape mode, we can show the
            // dialog in-line with the list so we don't need this activity.
            finish();
            return;
        }

        if (savedInstanceState == null) {
            // During initial setup, plug in the details fragment.
            DetailsFragment details = new DetailsFragment();
            details.setArguments(getIntent().getExtras());
            getFragmentManager().beginTransaction().add(android.R.id.content, details).commit();
        }
    } 
}

We should always try to prevent nullpointer exception , so we have to check first in saveinstance method for bundle information. for brief explaination to check this blog link

public static class DetailsActivity extends Activity {

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

        if (getResources().getConfiguration().orientation
            == Configuration.ORIENTATION_LANDSCAPE) {
            // If the screen is now in landscape mode, we can show the
            // dialog in-line with the list so we don't need this activity.
            finish();
            return;
        }

        if (savedInstanceState == null) {
            // During initial setup, plug in the details fragment.
            DetailsFragment details = new DetailsFragment();
            details.setArguments(getIntent().getExtras());
            getFragmentManager().beginTransaction().add(android.R.id.content, details).commit();
        }
    } 
}

回复收藏 0 原文

眼泪都笑了 2024-12-27 13:20:59

如果你只是做一个项目，那么项目经理说你需要实现屏幕切换功能，但是你不想在屏幕切换时加载不同的布局（可以创建layout和layout-port系统。

你会自动判断屏幕状态，加载对应布局），因为需要重新初始化activity或者fragment，用户体验不好，不能直接在屏幕上切换，我参考
？网址=YgNfP-vHy-Nuldi7YHTfNet3AtLdN-w__O3z1wLOnzr3wDjYo7X7PYdNyhw8R24ZE22xiKnydni7 R0r35s2fOLcHOiLGYT9Qh_fjqtytJki&wd=&eqid=f258719e0001f24000000004585a1082

前提是你的布局使用了layout_weight的布局权重方式，如下：

<LinearLayout
Android:id= "@+id/toplayout"
Android:layout_width= "match_parent"
Android:layout_height= "match_parent"
Android:layout_weight= "2"
Android:orientation= "horizontal" >

所以我的做法是，当屏幕切换时，不需要加载新的布局视图文件，在onConfigurationChanged动态修改布局权重，步骤如下：
1.首先设置：AndroidManifest.xml中的activity属性：android:configChanges=”keyboardHidden|orientation|screenSize”
防止屏幕切换，避免重新加载，这样才能在onConfigurationChanged中监听到
2 重写activity或fragment中的onConfigurationChanged方法。

@Override
Public void onConfigurationChanged (Configuration newConfig) {
    Super.onConfigurationChanged (newConfig);
    SetContentView (R.layout.activity_main);
    if (newConfig.orientation == Configuration.ORIENTATION_LANDSCAPE) {
        //On the layout / / weight adjustment
        LinearLayout toplayout = (LinearLayout) findViewById (R.id.toplayout);
        LinearLayout.LayoutParams LP = new LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT, 0, 2.0f);
        Toplayout.setLayoutParams (LP);
        LinearLayout tradespace_layout = (LinearLayout) findViewById(R.id.tradespace_layout);
        LinearLayout.LayoutParams LP3 = new LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT, 0, 2.8f);
        Tradespace_layout.setLayoutParams (LP3);
    }
    else if (newConfig.orientation == Configuration.ORIENTATION_PORTRAIT)
    {
        //On the layout / / weight adjustment
        LinearLayout toplayout = (LinearLayout) findViewById (R.id.toplayout);
        LinearLayout.LayoutParams LP = new LayoutParams (LinearLayout.LayoutParams.MATCH_PARENT, 0, 2.8f);
        Toplayout.setLayoutParams (LP);
        LinearLayout tradespace_layout = (LinearLayout) findViewById (R.id.tradespace_layout);
        LinearLayout.LayoutParams LP3 = new LayoutParams (LinearLayout.LayoutParams.MATCH_PARENT, 0, 2.0f);
        Tradespace_layout.setLayoutParams (LP3);
    }
}

If you just do a project, then the project manager says you need to achieve switching function screen, but you don't want to screen switching load different layout (can create layout and layout-port system.

You will automatically determine the screen state, load the corresponding layout), because of the need to re initialize the activity or fragment, the user experience is not good, not directly on the screen switch, I refer to
? Url=YgNfP-vHy-Nuldi7YHTfNet3AtLdN-w__O3z1wLOnzr3wDjYo7X7PYdNyhw8R24ZE22xiKnydni7R0r35s2fOLcHOiLGYT9Qh_fjqtytJki&wd=&eqid=f258719e0001f24000000004585a1082

The premise is that your layout using the weight of the way the layout of the layout_weight, as follows:

<LinearLayout
Android:id= "@+id/toplayout"
Android:layout_width= "match_parent"
Android:layout_height= "match_parent"
Android:layout_weight= "2"
Android:orientation= "horizontal" >

So my approach is, when screen switching, don't need to load a new layout of the view file, modify the layout in onConfigurationChanged dynamic weights, the following steps:
1 first set: AndroidManifest.xml in the activity attribute: android:configChanges= "keyboardHidden|orientation|screenSize"
To prevent screen switching, avoid re loading, so as to be able to monitor in onConfigurationChanged
2 rewrite activity or fragment in the onConfigurationChanged method.

@Override
Public void onConfigurationChanged (Configuration newConfig) {
    Super.onConfigurationChanged (newConfig);
    SetContentView (R.layout.activity_main);
    if (newConfig.orientation == Configuration.ORIENTATION_LANDSCAPE) {
        //On the layout / / weight adjustment
        LinearLayout toplayout = (LinearLayout) findViewById (R.id.toplayout);
        LinearLayout.LayoutParams LP = new LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT, 0, 2.0f);
        Toplayout.setLayoutParams (LP);
        LinearLayout tradespace_layout = (LinearLayout) findViewById(R.id.tradespace_layout);
        LinearLayout.LayoutParams LP3 = new LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT, 0, 2.8f);
        Tradespace_layout.setLayoutParams (LP3);
    }
    else if (newConfig.orientation == Configuration.ORIENTATION_PORTRAIT)
    {
        //On the layout / / weight adjustment
        LinearLayout toplayout = (LinearLayout) findViewById (R.id.toplayout);
        LinearLayout.LayoutParams LP = new LayoutParams (LinearLayout.LayoutParams.MATCH_PARENT, 0, 2.8f);
        Toplayout.setLayoutParams (LP);
        LinearLayout tradespace_layout = (LinearLayout) findViewById (R.id.tradespace_layout);
        LinearLayout.LayoutParams LP3 = new LayoutParams (LinearLayout.LayoutParams.MATCH_PARENT, 0, 2.0f);
        Tradespace_layout.setLayoutParams (LP3);
    }
}

回复收藏 0 原文

终遇你 2024-12-27 13:20:59

配置更改时，框架将为您创建片段的新实例并将其添加到活动中。因此，不要这样做：这样

FragmentOne fragment = new FragmentOne();

fragmentTransaction.add(R.id.fragment_container, fragment);

做：

if (mFragmentManager.findFragmentByTag(FRAG1_TAG) == null) {
    FragmentOne fragment = new FragmentOne();

    fragmentTransaction.add(R.id.fragment_container, fragment, FRAG1_TAG);
}

请注意，框架会在方向更改时添加 FragmentOne 的新实例，除非您调用 setRetainInstance(true)，在这种情况下，它将添加 FragmentOne 的旧实例。

On configuration change, the framework will create a new instance of the fragment for you and add it to the activity. So instead of this:

FragmentOne fragment = new FragmentOne();

fragmentTransaction.add(R.id.fragment_container, fragment);

do this:

if (mFragmentManager.findFragmentByTag(FRAG1_TAG) == null) {
    FragmentOne fragment = new FragmentOne();

    fragmentTransaction.add(R.id.fragment_container, fragment, FRAG1_TAG);
}

Please note that the framework adds a new instance of FragmentOne on orientation change unless you call setRetainInstance(true), in which case it will add the old instance of FragmentOne.

回复收藏 0 原文

~没有更多了~