使用commitAllowingStateLoss解决"无法在onSaveInstanceState之后执行此操作"的任何副作用

Question

以前,我们没有问题显示以下内容 DialogFragment

// Triggered by button click.
private void openFromCloud() {      
    LoadFromCloudTaskFragment loadFromCloudTaskFragment = new LoadFromCloudTaskFragment();
    FragmentManager fm = this.getSupportFragmentManager();
    fm.beginTransaction().add(loadFromCloudTaskFragment, "loadFromCloudTaskFragment").commit(); 
}

但是,如果我们DialogFragment在按下下面的OK按钮后显示相同的内容Intent,则会发生错误.

private void openFromCloud() {      
    startActivityForResult(Utils.getGoogleAccountCredential().newChooseAccountIntent(), REQUEST_ACCOUNT_PICKER);
}

@Override
protected void onActivityResult(final int requestCode, final int resultCode, final Intent data) {
    switch (requestCode) {
    case REQUEST_ACCOUNT_PICKER:
        if (resultCode == RESULT_OK && data != null && data.getExtras() != null) {
            String accountName = data.getStringExtra(AccountManager.KEY_ACCOUNT_NAME);
            if (accountName != null) {
                Utils.getGoogleAccountCredential().setSelectedAccountName(accountName);
                LoadFromCloudTaskFragment loadFromCloudTaskFragment = new LoadFromCloudTaskFragment();
                FragmentManager fm = getSupportFragmentManager();
                fm.beginTransaction().add(loadFromCloudTaskFragment, "loadFromCloudTaskFragment").commit();
            }
        }
    break;
    }
}

---

这是详细的错误日志

FATAL EXCEPTION: main
java.lang.RuntimeException: Failure delivering result ResultInfo{who=null, request=1, result=-1, data=Intent { (has extras) }} to activity {org.yccheok.xxx.gui/org.yccheok.xxx.gui.XXXFragmentActivity}: java.lang.IllegalStateException: Can not perform this action after onSaveInstanceState
    at android.app.ActivityThread.deliverResults(ActivityThread.java:3141)
    at android.app.ActivityThread.handleSendResult(ActivityThread.java:3184)
    at android.app.ActivityThread.access$1100(ActivityThread.java:130)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1243)
    at android.os.Handler.dispatchMessage(Handler.java:99)
    at android.os.Looper.loop(Looper.java:137)
    at android.app.ActivityThread.main(ActivityThread.java:4745)
    at java.lang.reflect.Method.invokeNative(Native Method)
    at java.lang.reflect.Method.invoke(Method.java:511)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
    at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.IllegalStateException: Can not perform this action after onSaveInstanceState
    at android.support.v4.app.FragmentManagerImpl.checkStateLoss(FragmentManager.java:1299)
    at android.support.v4.app.FragmentManagerImpl.enqueueAction(FragmentManager.java:1310)
    at android.support.v4.app.BackStackRecord.commitInternal(BackStackRecord.java:541)
    at android.support.v4.app.BackStackRecord.commit(BackStackRecord.java:525)
    at org.yccheok.xxx.gui.XXXFragmentActivity$1.run(XXXFragmentActivity.java:107)
    at android.app.Activity.runOnUiThread(Activity.java:4591)
    at org.yccheok.xxx.gui.XXXFragmentActivity.onActivityResult(XXXFragmentActivity.java:102)
    at android.app.Activity.dispatchActivityResult(Activity.java:5192)
    at android.app.ActivityThread.deliverResults(ActivityThread.java:3137)
    ... 11 more

我可以通过使用commitAllowingStateLoss而不是来简单地"解决"问题commit.

fm.beginTransaction().add(loadFromCloudTaskFragment, "loadFromCloudTaskFragment").commitAllowingStateLoss();

我真的不明白有关的文档commitAllowingStateLoss.

与commit()类似,但允许在保存活动状态后执行提交.这很危险,因为如果活动需要稍后从其状态恢复,则提交可能会丢失,因此这应该仅用于UI状态可以在用户上意外更改的情况.

这是基于获得异常的建议"IllegalStateException:onSaveInstanceState之后无法执行此操作"

我真的不明白UI状态是否可以在用户上意外更改.？我可以知道使用可能产生的副作用是commitAllowingStateLoss什么？我可以产生这种副作用的任何步骤吗？

Answer 1

我唯一能想到的是一种"竞争条件"事件.

想象一下当设备在您commitAllowingStateLoss()通话之前旋转时的情况.AFAIK,发生以下情况:

• onSaveInstanceState()回调(活动存储它的状态,此刻没有片段存在(因为你还没有提交任何东西)
• commitAllowingStateLoss执行时将片段添加到活动中
• Activity重新创建,恢复它的状态,当没有添加你的片段时

在我看来,它导致难以预测的情况,例如:

• java.lang.IllegalStateException: Failure saving state: FragmentB has target not in fragment manager: FragmentA如果你Fragment.setTargetFragment()因任何原因使用
• 您的片段可能只是从视图中丢失

无论如何,我对此并不是百分之百确定,但java.lang.IllegalStateException: Can not perform this action after onSaveInstanceState我的应用程序中有很多意外的异常,并试图找到解决方案.