java - Android Java - 在类中更改 requestLocationUpdates 刷新

Question

我在下面有这个类 GPS_Service。它工作完美。在 MainActivity 中，我可以更改变量 GPS_Service.gpsupdatedelay 的值，以调整通过 GPS_Service 中的 requestLocationUpdates 调用 GPS 的频率。在 MainActivity 中，我通过 GPS_Service.gpsupdatedelay = 10000 更改值；我想我还需要调用 GPS_Service 的某些方面来使变量值发生变化？我看不到调用 GPS_Service.onCreate() 的方法，我也不认为我应该这样做吗？

问题:在调整了 gpsupdatedelay 的值后，如何才能使 requestLocationUpdates 参数中的变量值发生变化并实际调整 GPS 频率？

提前谢谢你。

import android.app.Service;
import android.content.Context;
import android.content.Intent;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;
import android.os.IBinder;
import android.provider.Settings;
import android.support.annotation.Nullable;
import android.util.Log;
import android.widget.Toast;

public class GPS_Service extends Service {
    private LocationListener listener;
    private LocationManager locationManager;
    public static Integer gpsupdatedelay;

    @Nullable
    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }
    @Override
    public void onCreate() {
        Log.e("GPS","onCreate");
        listener = new LocationListener() {
            @Override
            public void onLocationChanged(Location location) {
                Intent i = new Intent("location_update");
                //i.putExtra("coordinates",location.getLongitude()+" "+location.getLatitude());

                i.putExtra("coordinate1",location.getLatitude());
                i.putExtra("coordinate2",location.getLongitude());
                Log.e("GPS","sendBroadcast");
                sendBroadcast(i);
            }
            @Override
            public void onStatusChanged(String s, int i, Bundle bundle) {
            }
            @Override
            public void onProviderEnabled(String s) {
            }
            @Override
            public void onProviderDisabled(String s) {
                Intent i = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);
                i.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                startActivity(i);
            }
        };
        locationManager = (LocationManager) getApplicationContext().getSystemService(Context.LOCATION_SERVICE);
        //noinspection MissingPermission
        locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER,gpsupdatedelay,0,listener);
    }
    @Override
    public void onDestroy() {
        super.onDestroy();
        if(locationManager != null){
            //noinspection MissingPermission
            locationManager.removeUpdates(listener);
        }
    }
}

Answer 1

您实际上不应该将 gpsupdatedelay 变量定义为静态。不要将它定义为静态并直接从 Activity 访问它，而是在需要更新它时将新值作为 Intent Extra 发送。

第一步是定义 onStartCommand() 方法覆盖，它将更新新的间隔值，取消注册旧的位置监听器，并使用新的间隔重新注册位置更新:

public class GPS_Service extends Service {
    private LocationListener listener;
    private LocationManager locationManager;
    public Integer gpsupdatedelay = 10000; //NOT static!

    @Nullable
    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }

    //Added:
    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        int newGpsUpdateDelay = intent.getIntExtra("new_gps_update_delay", -99);
        if (newGpsUpdateDelay != -99 && locationManager != null) {
            gpsupdatedelay = newGpsUpdateDelay;
            //noinspection MissingPermission
            locationManager.removeUpdates(listener);
            //noinspection MissingPermission
            locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER,gpsupdatedelay,0,listener);
        }
        return START_STICKY;
    }

    @Override
    public void onCreate() {
        Log.e("GPS","onCreate");
        listener = new LocationListener() {
            @Override
            public void onLocationChanged(Location location) {
                Intent i = new Intent("location_update");
                //i.putExtra("coordinates",location.getLongitude()+" "+location.getLatitude());

                i.putExtra("coordinate1",location.getLatitude());
                i.putExtra("coordinate2",location.getLongitude());
                Log.e("GPS","sendBroadcast");
                sendBroadcast(i);
            }
            @Override
            public void onStatusChanged(String s, int i, Bundle bundle) {
            }
            @Override
            public void onProviderEnabled(String s) {
            }
            @Override
            public void onProviderDisabled(String s) {
                Intent i = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);
                i.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                startActivity(i);
            }
        };
        locationManager = (LocationManager) getApplicationContext().getSystemService(Context.LOCATION_SERVICE);
        //noinspection MissingPermission
        locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER,gpsupdatedelay,0,listener);
    }
    @Override
    public void onDestroy() {
        super.onDestroy();
        if(locationManager != null){
            //noinspection MissingPermission
            locationManager.removeUpdates(listener);
        }
    }
}

为了更新来自 Activity 的值，只需创建一个 Intent，将新值放入 new_gps_update_delay Extra，然后调用 startService() 以发送服务的更新信息:

    int newDelay = 678;
    Intent i = new Intent(this, GPS_Service.class);
    i.putExtra("new_gps_update_delay", newDelay);
    startService(i);

这是有效的，因为即使服务已经在运行，也可以调用 startService() 方法。如果该服务已经在运行，基本上它只是运行 onStartCommand() 方法覆盖。

来自 the documentation for startService() :

If this service is not already running, it will be instantiated and started (creating a process for it if needed); if it is running then it remains running.

Every call to this method will result in a corresponding call to the target service's onStartCommand(Intent, int, int) method, with the intent given here. This provides a convenient way to submit jobs to a service without having to bind and call on to its interface.