使用兼容性包以Fragments为目标2.2。
重新编码 Activity 以在应用程序中使用片段后,我无法进行方向更改/状态管理,因此我创建了一个具有单个FragmentActivity和单个Fragment的小型测试应用程序。
来自方向更改的日志很奇怪,有多个对片段OnCreateView的调用。
我显然缺少了一些东西-例如分离片段并重新附加片段,而不是创建新实例,但是我看不到任何文档来表明我要去哪里。
任何人都可以告诉我我在做什么错。
谢谢
方向更改后,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
主要 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();
}
和碎片
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());
}
显现
<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>
最佳答案
您正在将片段一个接一个地分层。
发生配置更改时,旧的Fragment在重新创建时会将其自身添加到新的Activity中。在大多数情况下,这是后方的巨大痛苦。
您可以通过使用相同的片段而不是重新创建一个片段来阻止发生的错误。只需添加以下代码:
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
}
不过请注意:如果尝试从Fragment内访问“ Activity View ”,则会发生问题,因为生命周期会发生细微变化。 (从片段获取父 Activity 的 View 并不容易)。