[英]Image.network throw error even after defining errorBuilder in Flutter
[英]empty mLastKnownLocation even after defining @NonNull
我正在嘗試從這段代碼中獲取設備位置
private void getDeviceLocation() {
/*
* Get the best and most recent location of the device, which may be null in rare
* cases when a location is not available.
*/
try {
if (mLocationPermissionGranted) {
Task<Location> locationResult = mFusedLocationProviderClient.getLastLocation();
locationResult.addOnCompleteListener(getActivity(), new OnCompleteListener<Location>() {
@Override
public void onComplete(@NonNull Task<Location> task) {
if (task.isSuccessful()) {
mMap.clear();
// Set the map's camera position to the current location of the device.
mLastKnownLocation = task.getResult();
mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(
new LatLng(mLastKnownLocation.getLatitude(),
mLastKnownLocation.getLongitude()), DEFAULT_ZOOM));
} else {
Log.d(TAG, "Current location is null. Using defaults.");
Log.e(TAG, "Exception: %s", task.getException());
mMap.moveCamera(CameraUpdateFactory
.newLatLngZoom(mDefaultLocation, DEFAULT_ZOOM));
mMap.getUiSettings().setMyLocationButtonEnabled(false);
}
}
});
通常可以正常工作,但有時會引發以下錯誤:
java.lang.NullPointerException: Attempt to invoke virtual method 'double android.location.Location.getLatitude()' on a null object reference
at SecondFragment$1.onComplete(SecondFragment.java:230)
代碼的第230行是:
mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(
new LatLng(mLastKnownLocation.getLatitude(), //Line230
mLastKnownLocation.getLongitude()), DEFAULT_ZOOM));
我什至不理解@NonNull屏蔽后,代碼如何在這里出現並給出nullpoint異常。
此外,僅在仿真器中會出現此問題。 在真實設備中,我沒有發現此錯誤(即應用程序沒有像在模擬器中那樣崩潰)
NonNull表示返回的值不為null。 這並不意味着函數的返回值(例如getResult())不能為null。
另外,無論如何包裝,getLastKnownLocation始終可以返回null。 如果要確保獲得位置,請使用getSingleUpdate並等待回調。
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.