我在还原嵌套片段的状态时遇到问题。这是层次结构:MainActivity
----> AlarmOverviewFragment
(实际上没有保存任何重要数据)
--------> AlarmFragment
(保存数据)
我遇到的问题是,当我最小化应用程序(按“主页”按钮)然后重新打开应用程序时,每次尝试从作为Fragment
实例变量之一存储在。
令人沮丧的是,我将实例变量保存在onCreateView()
中,但是onSaveInstanceState()
在savedInstanceState
,onCreateView()
和onCreate()
中始终为null。
显然,我在这里错过了一些巨大的东西,因为我尝试了许多关于stackoverflow的解决方案,但无济于事。以下是一些相关的代码位:
保存实例数据:
@Override
public void onSaveInstanceState(Bundle outState) {
outState.putInt("hour", this.hour);
outState.putInt("window", this.window);
outState.putInt("minutes", this.minutes);
outState.putBooleanArray("days", this.days);
super.onSaveInstanceState(outState);
}
尝试还原数据失败
@Override
public void onCreate(Bundle savedInstanceState) {
if (savedInstanceState != null) {
/* Never happens */
hour = savedInstanceState.getInt("hour");
window = savedInstanceState.getInt("window");
minutes = savedInstanceState.getInt("minutes");
days = savedInstanceState.getBooleanArray("days");
}
super.onCreate(savedInstanceState);
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
if (savedInstanceState != null) {
/* Also never happens */
}
super.onActivityCreated(savedInstanceState);
}
为了以防万一,这是堆栈跟踪:
E/AndroidRuntime: FATAL EXCEPTION: main
Process: group12.wakemeup, PID: 22756
java.lang.RuntimeException: Unable to resume activity {group12.wakemeup/group12.wakemeup.MainActivity}: java.lang.NullPointerException: Attempt to read from null array
at android.app.ActivityThread.performResumeActivity(ActivityThread.java:3121)
at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:3152)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1400)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5525)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:730)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:620)
Caused by: java.lang.NullPointerException: Attempt to read from null array
at group12.wakemeup.AlarmFragment.onCreateView(AlarmFragment.java:113)
at android.support.v4.app.Fragment.performCreateView(Fragment.java:2087)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1113)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1295)
at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:801)
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1682)
at android.support.v4.app.FragmentController.execPendingActions(FragmentController.java:388)
at android.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:607)
at android.support.v7.app.AppCompatActivity.onStart(AppCompatActivity.java:181)
at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1237)
at android.app.Activity.performStart(Activity.java:6288)
at android.app.Activity.performRestart(Activity.java:6334)
at android.app.Activity.performResume(Activity.java:6339)
at android.app.ActivityThread.performResumeActivity(ActivityThread.java:3110)
at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:3152)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1400)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5525)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:730)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:620)
编辑
额外的信息
每个
onActivityCreated()
是动态添加的,并通过AlarmFragment
指定了唯一的ID,因此我不确定如何将每个片段保存在View.generateViewId()
中。还值得一提的是,我确实使用MainActivity
来处理选项卡/刷卡操作(此应用程序中还有其他Overview片段,但我将它们省略了,因为它们不会给我带来麻烦)。我听说有一种使用FragmentPagerAdapter
保存状态的方法,也许还有一种使用ViewPager
的状态? 最佳答案
由于问题似乎与开始时有所不同,因此实际上您不必每次都在onNewIntent
中重新创建片段。
您可以改为:
@Override
protected void onNewIntent(Intent intent) {
super.onNewIntent(intent);
if ("some_action".equals(intent.getAction())) {
//your action, in your case create and assign fragment
//remove the action
intent.setAction(null);
}
}