我创建了一个助手类，其中我有位置谷歌播放服务功能的所有初始化。当onLocationChanged被调用时，我调用一个接口onLocationChangedFunction。但是，由于空指针异常，它永远不会调用它。
这是我的代码：
public class LocationHelperClass implements GoogleApiClient.ConnectionCallbacks, GoogleApiClient.OnConnectionFailedListener, LocationListener {
private Context mContext;
private TaxiplonApp mApp;
private GoogleApiClient mGoogleApiClient;
private Location mLastLocation;
/**
* The desired interval for location updates. Inexact. Updates may be more or less frequent.
*/
private static final long UPDATE_INTERVAL_IN_MILLISECONDS = 10000;
/**
* The fastest rate for active location updates. Exact. Updates will never be more frequent
* than this value.
*/
private static final long FASTEST_UPDATE_INTERVAL_IN_MILLISECONDS =
UPDATE_INTERVAL_IN_MILLISECONDS / 2;
/**
* Stores parameters for requests to the FusedLocationProviderApi.
*/
private LocationRequest mLocationRequest;
public static LocationChangeListener locationListener;
public LocationHelperClass(Context context, TaxiplonApp app) {
super();
this.mContext = context;
this.mApp = app;
createInstanceGoogleAPIClient();
}
private void createInstanceGoogleAPIClient() {
if (mGoogleApiClient == null) {
mGoogleApiClient = new GoogleApiClient.Builder(mContext)
.addConnectionCallbacks(this)
.addOnConnectionFailedListener(this)
.addApi(LocationServices.API)
.build();
createLocationRequest();
}
}
/**
* Sets up the location request. Android has two location request settings:
* {@code ACCESS_COARSE_LOCATION} and {@code ACCESS_FINE_LOCATION}. These settings control
* the accuracy of the current location. This sample uses ACCESS_FINE_LOCATION, as defined in
* the AndroidManifest.xml.
* <p/>
* When the ACCESS_FINE_LOCATION setting is specified, combined with a fast update
* interval (5 seconds), the Fused Location Provider API returns location updates that are
* accurate to within a few feet.
* <p/>
* These settings are appropriate for mapping applications that show real-time location
* updates.
*/
protected void createLocationRequest() {
mLocationRequest = new LocationRequest();
// Sets the desired interval for active location updates. This interval is
// inexact. You may not receive updates at all if no location sources are available, or
// you may receive them slower than requested. You may also receive updates faster than
// requested if other applications are requesting location at a faster interval.
mLocationRequest.setInterval(UPDATE_INTERVAL_IN_MILLISECONDS);
// Sets the fastest rate for active location updates. This interval is exact, and your
// application will never receive updates faster than this value.
mLocationRequest.setFastestInterval(FASTEST_UPDATE_INTERVAL_IN_MILLISECONDS);
mLocationRequest.setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY);
}
/**
* Requests location updates from the FusedLocationApi.
*/
protected void startLocationUpdates() {
// The final argument to {@code requestLocationUpdates()} is a LocationListener
// (http://developer.android.com/reference/com/google/android/gms/location/LocationListener.html).
if (ActivityCompat.checkSelfPermission(mContext, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED
&& ActivityCompat.checkSelfPermission(mContext, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
// TODO: Consider calling
// ActivityCompat#requestPermissions
// here to request the missing permissions, and then overriding
// public void onRequestPermissionsResult(int requestCode, String[] permissions,
// int[] grantResults)
// to handle the case where the user grants the permission. See the documentation
// for ActivityCompat#requestPermissions for more details.
return;
}
LocationServices.FusedLocationApi.requestLocationUpdates(mGoogleApiClient, mLocationRequest, this);
}
/**
* Removes location updates from the FusedLocationApi.
*/
protected void stopLocationUpdates() {
// It is a good practice to remove location requests when the activity is in a paused or
// stopped state. Doing so helps battery performance and is especially
// recommended in applications that request frequent location updates.
// The final argument to {@code requestLocationUpdates()} is a LocationListener
// (http://developer.android.com/reference/com/google/android/gms/location/LocationListener.html).
LocationServices.FusedLocationApi.removeLocationUpdates(mGoogleApiClient, this);
}
public void clientConnect(){
mGoogleApiClient.connect();
}
public void clientDisconnect(){
mGoogleApiClient.disconnect();
}
@Override
public void onConnected(@Nullable Bundle bundle) {
if (ActivityCompat.checkSelfPermission(mContext, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED
&& ActivityCompat.checkSelfPermission(mContext, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
return;
}
Location mLastLocation = LocationServices.FusedLocationApi.getLastLocation(mGoogleApiClient);
if (mLastLocation != null) {
Toast.makeText(mContext, "Latitude: "+String.valueOf(mLastLocation.getLatitude())+" - Longtitude: "+String.valueOf(mLastLocation.getLongitude()), Toast.LENGTH_SHORT).show();
mApp.setLastKnownLocation(mLastLocation);
}
startLocationUpdates();
}
@Override
public void onConnectionSuspended(int i) {
}
@Override
public void onConnectionFailed(@NonNull ConnectionResult connectionResult) {
}
@Override
public void onLocationChanged(Location location) {
DebugLogger.debug("Location Changed called in Helper Class");
if(locationListener!=null){
locationListener.onLocationChangedFunction(location);
}
}
public interface LocationChangeListener {
void onLocationChangedFunction(Location location);
}
}
我为我的活动实现了这个监听器并onCreate
像这样初始化它：
location = new LocationHelperClass(this, (TaxiplonApp) getApplication());
但是，正如我所说，onLocationChangedFunction在我的活动中从未调用过。
12-21 17:48:28.100 4634-4634/? E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.taxiplon.taxi.driver.lit.taxiplondriver, PID: 4634
java.lang.NullPointerException: Attempt to invoke interface method 'void com.taxiplon.taxi.driver.lit.taxiplondriver.HelperClasses.LocationHelperClass$LocationChangeListener.onLocationChangedFunction(android.location.Location)' on a null object reference
at com.taxiplon.taxi.driver.lit.taxiplondriver.HelperClasses.LocationHelperClass.onLocationChanged(LocationHelperClass.java:166)
at com.google.android.gms.internal.zzart$zzb$1.zza(Unknown Source)
at com.google.android.gms.internal.zzart$zzb$1.zzs(Unknown Source)
at com.google.android.gms.internal.zzaaz.zzb(Unknown Source)
at com.google.android.gms.internal.zzaaz$zza.handleMessage(Unknown Source)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5294)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:904)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:699)