Question

我发现这个类我想用来获取位置更新，但我试图找出如何在位置更新时实现对活动的回调。我是否使用一些回调或其他类型的方法来实现它？

注意我从http://www.androidhive.info/2012/07/android-gps-location-manager-tutorial/

获取了代码

GPSTracker.java
package com.example.gpstracking;

import android.app.AlertDialog;
import android.app.Service;
import android.content.Context;
import android.content.DialogInterface;
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.util.Log;

public class GPSTracker extends Service implements LocationListener {

    private final Context mContext;

    // flag for GPS status
    boolean isGPSEnabled = false;

    // flag for network status
    boolean isNetworkEnabled = false;

    // flag for GPS status
    boolean canGetLocation = false;

    Location location; // location
    double latitude; // latitude
    double longitude; // longitude

    // The minimum distance to change Updates in meters
    private static final long MIN_DISTANCE_CHANGE_FOR_UPDATES = 10; // 10 meters

    // The minimum time between updates in milliseconds
    private static final long MIN_TIME_BW_UPDATES = 1000 * 60 * 1; // 1 minute

    // Declaring a Location Manager
    protected LocationManager locationManager;

    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;
                // 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;
    }

    /**
     * Stop using GPS listener
     * Calling this function will stop using GPS in your app
     * */
    public void stopUsingGPS(){
        if(locationManager != null){
            locationManager.removeUpdates(GPSTracker.this);
        }
    }

    /**
     * Function to get latitude
     * */
    public double getLatitude(){
        if(location != null){
            latitude = location.getLatitude();
        }

        // return latitude
        return latitude;
    }

    /**
     * Function to get longitude
     * */
    public double getLongitude(){
        if(location != null){
            longitude = location.getLongitude();
        }

        // return longitude
        return longitude;
    }

    /**
     * Function to check GPS/wifi enabled
     * @return boolean
     * */
    public boolean canGetLocation() {
        return this.canGetLocation;
    }

    /**
     * Function to show settings alert dialog
     * On pressing Settings button will lauch Settings Options
     * */
    public void showSettingsAlert(){
        AlertDialog.Builder alertDialog = new AlertDialog.Builder(mContext);

        // Setting Dialog Title
        alertDialog.setTitle("GPS is settings");

        // Setting Dialog Message
        alertDialog.setMessage("GPS is not enabled. Do you want to go to settings menu?");

        // On pressing Settings button
        alertDialog.setPositiveButton("Settings", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog,int which) {
                Intent intent = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);
                mContext.startActivity(intent);
            }
        });

        // on pressing cancel button
        alertDialog.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int which) {
            dialog.cancel();
            }
        });

        // Showing Alert Message
        alertDialog.show();
    }

    @Override
    public void onLocationChanged(Location location) {
    }

    @Override
    public void onProviderDisabled(String provider) {
    }

    @Override
    public void onProviderEnabled(String provider) {
    }

    @Override
    public void onStatusChanged(String provider, int status, Bundle extras) {
    }

    @Override
    public IBinder onBind(Intent arg0) {
        return null;
    }

}

Answer 1

一些注意事项：

默认情况下，服务在UI线程上运行。如果从特定源获取位置需要很长时间，则此类可能会阻止您的UI。您多久需要更新一次？您可以运行计时器向IntentService发送请求以获取GPS信息。
如果你真的需要GPS“跟踪”，那么你做的是正确的，但要记住GPS快速耗尽电池。
从一个Android组件到另一个组件进行通信的最佳方式是使用BroadcastReceiver。这提供了一个清晰，直接的回调，可以处理来自各种组件的多条“消息”。

Answer 2

此代码可用于使用您的GPSTracker类获取位置，将您的代码粘贴到您的活动onCreate方法以进行测试。是的，它现在会阻止您的UI线程，但您将获得该位置。之后，您可以阅读有关在Android中使用Service以获得更好的想法的信息。

            LocationResult locationResult = new LocationResult() {
                @Override
                public void gotLocation(Location location) {
                    Log.d("Activity","In gotLocation Listener");
                    boolean hasAddedQr = false;
                    if(hasAddedQr){
                        return;
                    }
                    hasAddedQr = true;
                    if (location != null) {
                        Log.d("Activity","Got the location");

                        // Got the location!
                        try {

                            double lati = location.getLatitude();
                            double longi = location.getLongitude();

                            text.setText("Got Location: La="+lati+", Lo="+longi);
                        } catch (Exception e) {
                            // TODO: handle exception
                        }
                    } else {
                        GetLocation.this.runOnUiThread(new Runnable() {

                            @Override
                            public void run() {
                                // TODO Auto-generated method stub
                                text.setText("Location was returned null");

                            }
                        });
                    }
                }
            };
            GPSTracker myLocation = new GPSTracker();
            boolean isEnabled = myLocation.getLocation(GetLocation.this, locationResult);
            if(!isEnabled){
                Log.d("Activity", "LOCATION SERVICES WERE NOT ENABLED");
                text.setText("Location service not available");
                getLocationBtn.setEnabled(true);

            }
            else{
                Log.d("Activity", "LOCATION SERVICES ENABLED");

            }

Answer 3

是的，你应该添加一个类似的回调方法：

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

  this.calleractivity=calleractivity
}

您的更新方法类似于

 public void update(){
       calleractivity.getback();
    }

在你的活动中：

gps = new GPSTracker(Context context, this);

我希望它有所帮助

java类在位置更新时回调活动

3 个答案: