按下按钮时，ShowActivities片段正在实例化。我第一次按下它一切正常。这是我在logCat中得到的：
11-16 23:41:12.560 25874-25874/name.company.newapp E/onCreate: getActivity() == null: false
11-16 23:41:12.560 25874-25874/name.company.newapp E/onCreate: Hash: 1036405628
11-16 23:41:12.570 25874-25874/name.company.newapp E/onCreateView: getActivity() == null: false
11-16 23:41:12.570 25874-25874/name.company.newapp E/onCreateView: Hash: 1036405628
11-16 23:41:12.630 25874-25874/name.company.newapp E/onConnected: getActivity() == null: false
11-16 23:41:12.630 25874-25874/name.company.newapp E/onConnected: Hash: 1036405628
一切都很好。我按后退键并返回上一个片段。现在我再次单击该按钮打开ShowActivities片段，现在logCat返回的是：
11-16 23:41:13.890 25874-25874/name.company.newapp E/onCreate: getActivity() == null: false
11-16 23:41:13.890 25874-25874/name.company.newapp E/onCreate: Hash: 252302789
11-16 23:41:13.890 25874-25874/name.company.newapp E/onCreateView: getActivity() == null: false
11-16 23:41:13.890 25874-25874/name.company.newapp E/onCreateView: Hash: 252302789
11-16 23:41:13.900 25874-25874/name.company.newapp E/onConnected: getActivity() == null: true
11-16 23:41:13.900 25874-25874/name.company.newapp E/onConnected: Hash: 1036405628
onConnected。
ShowActivities片段
public class ShowActivities extends Fragment implements
GoogleApiClient.ConnectionCallbacks, GoogleApiClient.OnConnectionFailedListener, LocationListener {
public ShowActivities() {
}
private static GoogleApiClient googleClient;
private Location mLastLocation;
private PendingResult<LocationSettingsResult> result;
private LocationRequest locationRequest;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Log.e("onCreate"," "+(getActivity() == null));
if (googleClient==null) {
googleClient = new GoogleApiClient.Builder(getActivity())
.addApi(LocationServices.API)
.addConnectionCallbacks(this)
.addOnConnectionFailedListener(this)
.build();
}
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
super.onCreateView(inflater, container, savedInstanceState);
Log.e("onCreateView"," "+(getActivity() == null));
// Defines the xml file for the fragment
View view = inflater.inflate(R.layout.upload_activity_fragment, container, false);
return view;
}
@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
}
@Override
public void onConnected(Bundle bundle) {
Log.e("onConnected"," "+(getActivity() == null));
locationRequest = LocationRequest.create();
locationRequest.setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY);
LocationSettingsRequest.Builder builder = new LocationSettingsRequest.Builder()
.addLocationRequest(locationRequest);
builder.setAlwaysShow(true);
result = LocationServices.SettingsApi.checkLocationSettings(googleClient, builder.build());
if (result != null) {
result.setResultCallback(new ResultCallback<LocationSettingsResult>() {
@Override
public void onResult(LocationSettingsResult locationSettingsResult) {
final Status status = locationSettingsResult.getStatus();
switch (status.getStatusCode()) {
case LocationSettingsStatusCodes.SUCCESS:
// All location settings are satisfied. The client can initialize location
// requests here.
break;
case LocationSettingsStatusCodes.RESOLUTION_REQUIRED:
// Location settings are not satisfied. But could be fixed by showing the user
// a optionsDialog.
try {
// Show the optionsDialog by calling startResolutionForResult(),
// and check the result in onActivityResult().
if (status.hasResolution()) {
status.startResolutionForResult(getActivity(), 1000);
Log.e("location", "Resolution");
}
} catch (IntentSender.SendIntentException e) {
// Ignore the error.
Log.e("location", "Resolution2");
}
break;
case LocationSettingsStatusCodes.SETTINGS_CHANGE_UNAVAILABLE:
// Location settings are not satisfied. However, we have no way to fix the
// settings so we won't show the optionsDialog.
break;
}
}
});
}
}
@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if ((resultCode == Activity.RESULT_OK) && (requestCode == 1000)) {
mLastLocation = LocationServices.FusedLocationApi.getLastLocation(googleClient);
}
}
@Override
public void onConnectionSuspended(int i) {
}
@Override
public void onConnectionFailed(ConnectionResult connectionResult) {
}
@Override
public void onLocationChanged(Location location) {
Log.e("location", "finally");
}
@Override
public void onResume() {
super.onResume();
}
@Override
public void onPause() {
super.onPause();
if (googleClient!=null) {
googleClient = null;
}
}
}
这已经解决了。一旦我退出片段，我修改了onPause以使googleClient为null。
答案 0 :(得分：0)
首先尝试通过TAG在占位符中获取Fragment实例，它没有先前的intance，然后创建一个实例。
Fragment ShowActivities = getFragmentManager().getFragmentByTag(YOUR_TAG);
if (showActivities == null) {
showActivities = new ShowActivities();
getFragmentManager().beginTransaction()
.replace(R.id.your_placeholder, showActivities, YOUR_TAG)
.addToBackStack(null)
.commit();
}
答案 1 :(得分：0)
首先，请更改onCreateView中的超级方法调用，以便调用super.onCreateView（...）。
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Defines the xml file for the fragment
View view = inflater.inflate(R.layout.upload_activity_fragment, container, false);
return view;
}
然后将此片段移至onActivityCreated（...）
client = new NightAssetRestClient(getActivity());
locationQueries = new LocationQueries(getActivity());
if (googleClient==null) {
googleClient = new GoogleApiClient.Builder(getActivity())
.addApi(LocationServices.API)
.addConnectionCallbacks(this)
.addOnConnectionFailedListener(this)
.build();
}
仍然，你需要在onConnect（...）中检查null，因为即使基础Activity被销毁，Async进程也可以保存这个Fragment的引用。
在onCreate方法中添加行setRetainInstance(boolean)可能会有所帮助。