Question

事实上，我无法确定哪个上下文作为参数传递给GPSTracker（上下文），这是一个错误。

我的接收者代码的一部分：

public class AlarmActivity extends BroadcastReceiver {
GPSTracker gps;
@Override
public void onReceive(Context context, Intent intent) {
        gps = new GPSTracker(context);//The context am using here is giving the error
        Log.i("happening","in alarm reciever class");
    }
}

GPSTracker类的一部分：

public class GPSTracker extends Service implements LocationListener {
private final Context mContext;

public GPSTracker(Context context) {
    this.mContext = context;
    getLocation();

public Location getLocation() {
    try {
        locationManager = (LocationManager) mContext
                .getSystemService(LOCATION_SERVICE);

        // getting GPS status
        isGPSEnabled = locationManager
                .isProviderEnabled(LocationManager.GPS_PROVIDER);

        // getting network status
        isNetworkEnabled = locationManager
                .isProviderEnabled(LocationManager.NETWORK_PROVIDER);

        if (!isGPSEnabled && !isNetworkEnabled) {
            // no network provider is enabled
        } else {
            this.canGetLocation = true;
            location.setAccuracy(3);
            // First get location from Network Provider
            if (isNetworkEnabled) {
                locationManager.requestLocationUpdates(
                        LocationManager.NETWORK_PROVIDER,
                        MIN_TIME_BW_UPDATES,
                        MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
                Log.d("Network", "Network");
                if (locationManager != null) {
                    location = locationManager
                            .getLastKnownLocation(LocationManager.NETWORK_PROVIDER);

                    if (location != null) {
                        latitude = location.getLatitude();
                        longitude = location.getLongitude();
                    }
                }
            }
            // if GPS Enabled get lat/long using GPS Services
            if (isGPSEnabled) {
                if (location == null) {

                    locationManager.requestLocationUpdates(
                            LocationManager.GPS_PROVIDER,
                            MIN_TIME_BW_UPDATES,
                            MIN_DISTANCE_CHANGE_FOR_UPDATES, this);

                    Log.d("GPS Enabled", "GPS Enabled");
                    if (locationManager != null) {
                        location = locationManager
                                .getLastKnownLocation(LocationManager.GPS_PROVIDER);
                        if (location != null) {
                            latitude = location.getLatitude();
                            longitude = location.getLongitude();
                        }
                    }
                }
            }
        }

    } catch (Exception e) {
        e.printStackTrace();
    }

    return location;
}
}

我收到以下错误：

03-03 12:23:47.819: W/System.err(1053): java.lang.NullPointerException
03-03 12:23:47.819: W/System.err(1053):     at com.example.mehweez.GPSTracker.getLocation(GPSTracker.java:64)
03-03 12:23:47.819: W/System.err(1053):     at com.example.mehweez.GPSTracker.<init>(GPSTracker.java:44)
03-03 12:23:47.819: W/System.err(1053):     at com.example.mehweez.AlarmActivity.onReceive(AlarmActivity.java:44)
03-03 12:23:47.829: W/System.err(1053):     at android.app.ActivityThread.handleReceiver(ActivityThread.java:2424)
03-03 12:23:47.829: W/System.err(1053):     at android.app.ActivityThread.access$1500(ActivityThread.java:141)
03-03 12:23:47.829: W/System.err(1053):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1332)
03-03 12:23:47.829: W/System.err(1053):     at android.os.Handler.dispatchMessage(Handler.java:99)
03-03 12:23:47.829: W/System.err(1053):     at android.os.Looper.loop(Looper.java:137)
03-03 12:23:47.829: W/System.err(1053):     at android.app.ActivityThread.main(ActivityThread.java:5103)
03-03 12:23:47.829: W/System.err(1053):     at java.lang.reflect.Method.invokeNative(Native Method)
03-03 12:23:47.839: W/System.err(1053):     at java.lang.reflect.Method.invoke(Method.java:525)
03-03 12:23:47.839: W/System.err(1053):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
03-03 12:23:47.839: W/System.err(1053):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
03-03 12:23:47.839: W/System.err(1053):     at dalvik.system.NativeStart.main(Native Method)

Answer 1

您似乎在setAccuracy()对象上调用了Location。这有两个问题：

您尚未初始化location数据成员。
调用setAccuracy()没用。

Answer 2

GPSTracker是一项服务，而AlarmActivity是一个broadcastReceiver，如果你需要从broadcastReceiver调用服务，你需要这个：

public class AlarmActivity extends BroadcastReceiver {
@Override
public void onReceive(Context context, Intent intent) {

       Intent myIntent=new Intent(context,GPSTracker.class);
       context.startService(myIntent);  
        Log.i("happening","in alarm reciever class");
    }
}

在扩展BroadcastReceiver的类中使用哪个上下文？

2 个答案: