我正在使用无头保留的任务片段来下载和处理数据，因此UI线程不会被阻止，并且可以优雅地处理配置更改。基本逻辑来自here和here，但是，我进行了更改以允许使用UI片段而不是UI活动。
有效。我唯一的问题是，在恢复后 - 我的应用程序被系统杀死后 - 任务片段在不应该运行时运行。对于这种类型的恢复，我已经从持久存储中恢复了数据，并且不想再次下载。但请注意，如果我之前单击了刷新，则只会发生任务片段的多余运行，从而创建了第一次使用任务片段。
这是我正在使用任务片段的地方：
private static final String TAG_TASK_FRAGMENT = "task_fragment_2";
private static httpGetFragment mTaskFragment;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setHasOptionsMenu(true);
System.err.println("onCreate ++++++++++++++");
// setup for headless task fragment; the rest is in runTaskFragment()
FragmentManager fm = getFragmentManager();
mTaskFragment = (httpGetFragment) fm.findFragmentByTag(TAG_TASK_FRAGMENT);
// If the Fragment is non-null, then it is currently being
// retained across a configuration change; sort of... it's non-null more than expected
if (mTaskFragment != null) {
System.err.println("mTaskFragment is NOT null. Tag = " + mTaskFragment.getTag() + " >>>>>>>>>");
mTaskFragment.setTargetFragment(this, 0);
}
}
然后，从按钮开始点击：
private void runTaskFragment() {
System.err.println("----------- Running task fragment from action_refresh click !!!!!");
setRefreshActionButtonState(true);
FragmentManager fm = getFragmentManager();
if (mTaskFragment == null) {
mTaskFragment = new httpGetFragment();
mTaskFragment.setTargetFragment(this, 0);
fm.beginTransaction().add(mTaskFragment, TAG_TASK_FRAGMENT).commit();
}
}
任务片段的onPostExecute（）回调调用：
private void finishTheRefresh(boolean successful) {
if (mTaskFragment != null) mTaskFragment = null;
System.err.println("&&&&&&&&&&& DONE !!! and mTaskFragment is NULL");
setRefreshActionButtonState(false);
if (successful) refreshDisplayList();
}
所以，现在到了logcat。这是Kill复兴，当先前没有运行刷新taskfragment时，它显示了所需的行为。请注意，在onResume（）中设置actionBar之后，系统会调用onNavigationItemSelected（）。顺便说一句，从SD恢复数据发生在应用程序对象中：
01-07 09:35:05.549 27324-27324/com... W/ManagedEGLContext? doTerminate failed: EGL count is 2 but managed count is 1
01-07 09:36:05.314 30423-30423/com... W/System.err? restoring data from SD %%%%%%%%%%%%%%%%
01-07 09:36:05.366 30423-30423/com... W/System.err? onCreate ++++++++++++++
01-07 09:36:05.571 30423-30463/com... W/chromium? [WARNING:proxy_service.cc(890)] PAC support disabled because there is no system implementation
01-07 09:36:05.591 30423-30423/com... W/art? Attempt to remove local SIRT entry from IRT, ignoring
01-07 09:36:05.617 30423-30474/com... W/art? Thread[19,tid=30474,Native,Thread*=0x48ebca50,peer=0x6535eb38,"Thread-54625"] attached without supplying a name
01-07 09:36:05.664 30423-30423/com... W/System.err? onResume +++++++++++++++++++
01-07 09:36:05.847 30423-30423/com... W/System.err? *** onNavigationItemSelected -- where we need to go on kill-revival, to update list adapter ***
01-07 09:36:05.850 30423-30423/com... W/InputMethodManager? Ignoring onBind: cur seq=16255, given seq=16254
01-07 09:36:05.977 30423-30487/com... W/art? Thread[21,tid=30487,Native,Thread*=0x4cf57b88,peer=0x653a7610,"Thread-54627"] attached without supplying a name
在这里，我点击刷新点击：
01-07 09:40:08.480 30423-30423/com... W/System.err? &&&&&&&&&&& Refresh CLick !!!!!!!!!!!!!
01-07 09:40:08.483 30423-30423/com... W/System.err? ----------- Running task fragment from action_refresh click !!!!!
01-07 09:40:09.770 30423-30423/com... W/System.err? *** Post-Execute for data download & extraction ***
01-07 09:40:09.772 30423-30423/com... W/System.err? &&&&&&&&&&& DONE !!! and mTaskFragment is NULL
而且，问题已经复制，数据已下载。没有按钮点击，并且运行了onPostExecute（）回调的taskfragment。 当我之前将任务片段搞定时，怎么会发生这种情况呢？
01-07 09:42:41.182 31645-31645/com... W/System.err? restoring data from SD %%%%%%%%%%%%%%%%
01-07 09:42:41.220 31645-31645/com... W/System.err? onCreate ++++++++++++++
01-07 09:42:41.220 31645-31645/com... W/System.err? mTaskFragment is NOT null. Tag = task_fragment_2 >>>>>>>>>
01-07 09:42:41.447 31645-31686/com... W/chromium? [WARNING:proxy_service.cc(890)] PAC support disabled because there is no system implementation
01-07 09:42:41.463 31645-31645/com... W/art? Attempt to remove local SIRT entry from IRT, ignoring
01-07 09:42:41.475 31645-31697/com... W/art? Thread[20,tid=31697,Native,Thread*=0x490354f0,peer=0x653769b0,"Thread-54681"] attached without supplying a name
01-07 09:42:41.494 31645-31645/com... W/System.err? onResume +++++++++++++++++++
01-07 09:42:41.652 31645-31645/com... W/System.err? *** onNavigationItemSelected -- where we need to go on kill-revival, to update list adapter ***
01-07 09:42:41.661 31645-31645/com... W/InputMethodManager? Ignoring onBind: cur seq=16279, given seq=16278
01-07 09:42:41.730 31645-31709/com... W/art? Thread[23,tid=31709,Native,Thread*=0x4b237a90,peer=0x653c5138,"Thread-54684"] attached without supplying a name
01-07 09:42:42.640 31645-31645/com... W/System.err? *** Post-Execute for data download & extraction ***
01-07 09:42:42.643 31645-31645/com... W/System.err? &&&&&&&&&&& DONE !!! and mTaskFragment is NULL
01-07 09:42:44.897 31645-31718/com... W/art? Thread[25,tid=31718,Native,Thread*=0x4cca44b0,peer=0x65579fb0,"Thread-54686"] attached without supplying a name
感谢您对这个谜团的考虑。我在logcat中留下了一些额外的警告，以防有人想要了解它们。我还是Android新手，还没有在有用的网络搜索中找到所有警告。
答案 0 :(得分：0)
似乎归零mTaskFragment还不足以消除它。使用片段事务首先删除片段，就可以了。所以，finishTheRefresh（）看起来像这样：
private void finishTheRefresh(boolean successful) {
//if (mTaskFragment != null) mTaskFragment = null;
if (mTaskFragment != null) {
FragmentManager fm = getFragmentManager();
fm.beginTransaction().remove(mTaskFragment).commit();
mTaskFragment = null;
}
setRefreshActionButtonState(false);
System.err.println("&&&&&&&&&&& DONE !!! and mTaskFragment is NULL");
if (successful) refreshDisplayList();
}
我相信这也会恢复更多记忆。