我遇到了一些麻烦，可以提供一些帮助。我有一个MapsActivity和一个LocationHelper类，但在加载MapsActivity时，我会看到下面列出的错误。
MapsActivity -
public class MapsActivity extends FragmentActivity implements OnMapReadyCallback {
private static final int MY_PERMISSIONS_REQUEST_ACCESS_FINE_LOCATION = 1;
private static final int MY_PERMISSIONS_REQUEST_ACCESS_COARSE_LOCATION = 2;
private GoogleMap mMap;
private LocationHelper locationHelper;
private LatLng location;
private boolean onCreateFinished = false;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
onCreateFinished = true;
setContentView(R.layout.activity_maps);
// Obtain the SupportMapFragment and get notified when the map is ready to be used.
SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()
.findFragmentById(R.id.map);
//instantiates LocationHelper for use in this activity
locationHelper = new LocationHelper(this);
//runs startConnection from LocationHelper class
locationHelper.startConnection();
//starts map
mapFragment.getMapAsync(this);
}
@Override
public void onMapReady(GoogleMap googleMap) {
mMap = googleMap;
// Add a marker in Sydney and move the camera
LatLng sydney = new LatLng(-34, 151);
mMap.addMarker(new MarkerOptions().position(sydney).title("Marker in Sydney"));
//mMap.moveCamera(CameraUpdateFactory.newLatLng(sydney));
}
//sets map markers
public void setMapMarkers(){
//runs checkLocation from LocationHelper class
locationHelper.checkLocation();
location = new LatLng(locationHelper.mLatitude, locationHelper.mLongitude);
LatLng currentLocation = new LatLng(location.latitude, location.longitude);
mMap.addMarker(new MarkerOptions().position(currentLocation).title("Your Location"));
mMap.moveCamera(CameraUpdateFactory.newLatLng(currentLocation));
}
@Override
protected void onStart() {
locationHelper.mGoogleApiClient.connect();
super.onStart();
}
@Override
protected void onResume() {
super.onResume();
if(onCreateFinished == true){
setMapMarkers();
}else{
Toast.makeText(this, "onCreate not finished..", Toast.LENGTH_SHORT).show();
}
}
@Override
protected void onStop() {
locationHelper.mGoogleApiClient.disconnect();
//LocationManager.removeUpdates();
super.onStop();
}
LocationHelper类 -
public class LocationHelper extends Activity implements GoogleApiClient.ConnectionCallbacks, GoogleApiClient.OnConnectionFailedListener {
//private static final int MY_PERMISSIONS_REQUEST_ACCESS_FINE_LOCATION = 1;
//private static final int MY_PERMISSIONS_REQUEST_ACCESS_COARSE_LOCATION = 2;
GoogleApiClient mGoogleApiClient;
private LocationManager mLocationManager;
//private Location mLastLocation;
private LocationListener mLocationListener;
public double mLatitude;
public double mLongitude;
private Context context;
//constructor
public LocationHelper(Context context) {
//saves the context received from activity that instantiates LocationHelper into a local variable
this.context = context;
}
public void startConnection() {
// Create an instance of GoogleAPIClient.
if (mGoogleApiClient == null) {
mGoogleApiClient = new GoogleApiClient.Builder(context)
.addConnectionCallbacks(this)
.addOnConnectionFailedListener(this)
.addApi(LocationServices.API)
.build();
}
}
public void checkLocation(){
//gets system service from LocationManager
mLocationManager = (LocationManager)getSystemService(LOCATION_SERVICE);
//checks permissions
if(ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED){
return;
}
mLocationListener = new LocationListener(){
@Override
public void onLocationChanged(Location location) {
//checks if GPS is enabled
if(mLocationManager.isProviderEnabled(LocationManager.GPS_PROVIDER)){
if(mLocationListener != null){
if(ActivityCompat.checkSelfPermission(getApplicationContext(), Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(getApplicationContext(), Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED){
return;
}
if (mLocationManager != null) {
location = mLocationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
if(location != null){
mLatitude = location.getLatitude();
mLongitude = location.getLongitude();
Toast.makeText(getApplicationContext(), "GPS - " + String.valueOf(mLatitude) + "," + String.valueOf(mLongitude), Toast.LENGTH_SHORT).show();
}
}
}
}
//checks if internet is enabled
else if(mLocationManager.isProviderEnabled(LocationManager.NETWORK_PROVIDER)){
if(mLocationManager != null){
location = mLocationManager.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
if(location != null){
mLatitude = location.getLatitude();
mLongitude = location.getLongitude();
Toast.makeText(getApplicationContext(), "NETWORK - " + String.valueOf(mLatitude) + "," + String.valueOf(mLongitude), Toast.LENGTH_SHORT).show();
}
}
}
//method for setting location request parameters
setLocationRequest();
}
@Override
public void onStatusChanged(String provider, int status, Bundle extras) {
}
@Override
public void onProviderEnabled(String provider) {
}
@Override
public void onProviderDisabled(String provider) {
}
};
}
@Override
public void onConnected(@Nullable Bundle bundle) {
}
@Override
public void onConnectionSuspended(int i) {
}
@Override
public void onConnectionFailed(@NonNull ConnectionResult connectionResult) {
}
public void setLocationRequest(){
//sets locationrequest parameters
LocationRequest mLocationRequest = new LocationRequest();
mLocationRequest.setInterval(5000);
mLocationRequest.setFastestInterval(3000);
mLocationRequest.setPriority(LocationRequest.PRIORITY_BALANCED_POWER_ACCURACY);
}
public double getLatitudeForNote() {
return mLatitude;
}
public double getLongitudeForNote(){
return mLongitude;
}
}
错误 -
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.a8460p.locationotes, PID: 1715
java.lang.RuntimeException: Unable to resume activity {com.example.a8460p.locationotes/com.example.a8460p.locationotes.MapsActivity}: java.lang.IllegalStateException: System services not available to Activities before onCreate()
at android.app.ActivityThread.performResumeActivity(ActivityThread.java:3160)
at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:3191)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2529)
at android.app.ActivityThread.access$900(ActivityThread.java:154)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1391)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:234)
at android.app.ActivityThread.main(ActivityThread.java:5526)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: java.lang.IllegalStateException: System services not available to Activities before onCreate()
at android.app.Activity.getSystemService(Activity.java:5300)
at com.example.a8460p.locationotes.LocationHelper.checkLocation(LocationHelper.java:66)
at com.example.a8460p.locationotes.MapsActivity.setMapMarkers(MapsActivity.java:71)
at com.example.a8460p.locationotes.MapsActivity.onResume(MapsActivity.java:88)
at android.app.Instrumentation.callActivityOnResume(Instrumentation.java:1259)
at android.app.Activity.performResume(Activity.java:6361)
at android.app.ActivityThread.performResumeActivity(ActivityThread.java:3149)
at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:3191)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2529)
at android.app.ActivityThread.access$900(ActivityThread.java:154)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1391)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:234)
at android.app.ActivityThread.main(ActivityThread.java:5526)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
提前感谢您的帮助！
答案 0 :(得分：1)
第1步：从extends Activity删除LocationHelper。这不是一项活动。
第2步：使用context来调用getSystemService()内的LocationHelper。
步骤3：确定您是否要使用Play服务SDK中的Android LocationManager 或 LocationRequest，并删除与该服务相关的所有代码你不打算用。
答案 1 :(得分：0)
您需要在onCreate完成后初始化您的LocationHelper实例。您可以将相关代码移动到onMapReady（）方法。