如何在 Android 中使用其位置跟踪一个人

Question

我正在做一个项目...我需要使用其地理位置（纬度，经度）跟踪一个人.. 场景： - 当位置发生变化时，人员 A 的位置正在 MYSQL DB 中的服务器上更新。 - B 需要通过他/她自己的设备（Android 手机）在 Google 地图上看到 A

问题

当我建立与服务器的连接并尝试从 MYSQL DB 获取位置时......连接被触发并且应用程序崩溃。 注意 人 B 需要跟踪，直到它到达特定点。 有没有其他方法可以做到这一点>？？ 感谢您提前提供帮助

从服务器下载跟踪位置

private class downloadTrackingLocationsAsync extends AsyncTask<String, Void, String> {
    @Override
    protected void onPreExecute() {
    }
    @Override
    protected String doInBackground(String... params) {
        String ID = params[1];
        HttpURLConnection conn = null;

        try {
            // create connection
            URL wsURL=new URL(params[0]);
            conn=(HttpURLConnection) wsURL.openConnection();
            conn.setRequestMethod("POST");
            conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
            conn.setUseCaches(false);

            Uri.Builder builder = new Uri.Builder().appendQueryParameter("id", ID);
            String data = builder.build().getEncodedQuery();
            byte[] outputInBytes = data.getBytes("UTF-8");
            conn.setRequestProperty("Content-Length", "" + Integer.toString(outputInBytes.length));
            conn.setDoOutput(true);
            conn.setDoInput(true);
            OutputStream os = conn.getOutputStream();
            os.write(outputInBytes);
            os.close();

            //get data
            InputStream bufferedInputStream = new BufferedInputStream(conn.getInputStream());
            // converting InputStream into String
            Scanner scanner = new Scanner(bufferedInputStream);
            String strJSON = scanner.useDelimiter("\\A").next();
            scanner.close();
            bufferedInputStream.close();
            return strJSON;

        } catch (MalformedURLException e) {
            e.printStackTrace(); // URL is invalid
        } catch (SocketTimeoutException e) {
            e.printStackTrace(); // data retrieval or connection timed out
        } catch (IOException e) {
            e.printStackTrace(); // could not read response body
            // (could not create input stream)
        } finally {
            if (conn != null) {conn.disconnect(); }
        }
        return null;
    }
    @Override
    protected void onPostExecute(String result) {
        if(result !=null) {
            try {
                JSONObject rootObject = new JSONObject(result);

                    double latitude = rootObject.optDouble("lattitude");
                    double longitude = rootObject.optDouble("longitude");

                    LatLng currentLocation = new LatLng(latitude, longitude);
                    PersonB_FragmentMap.updateTrackingLocation(currentLocation);
                Log.i("Location", currentLocation.toString());
                    Toast.makeText(context, "Tracking Location Downloaded", Toast.LENGTH_LONG).show();

            }catch (JSONException e){
                e.printStackTrace();
            }
        }
        else {
            Toast.makeText(context, "Result Null", Toast.LENGTH_SHORT).show();
        }
    }
}

我正在使用一个函数连续调用这个类

Answer 1

您应该使用 AlarmManager 和服务并在后台执行此操作。 更多AlarmManager详情refer this link

使用 AlarmManager、BroadcastReceiver、Service 和 Notification Manager 在后台进程中定期更新来自服务器的数据。

首先激活AlarmManager。在Activity类中写下代码

public class MainActivity extends ListActivity {

     private static final long REPEAT_TIME = 1000 * 30;

        @Override
        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.main);
            setRecurringAlarm(this);
        }

        private void setRecurringAlarm(Context context) {

            Calendar updateTime = Calendar.getInstance();
            updateTime.setTimeZone(TimeZone.getDefault());
            updateTime.set(Calendar.HOUR_OF_DAY, 12);
            updateTime.set(Calendar.MINUTE, 30);
            Intent downloader = new Intent(context, MyStartServiceReceiver.class);
            downloader.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);

            PendingIntent pendingIntent = PendingIntent.getBroadcast(context, 0, downloader,       PendingIntent.FLAG_CANCEL_CURRENT);

            AlarmManager alarmManager = (AlarmManager) getSystemService(Context.ALARM_SERVICE);

            alarmManager.setRepeating(AlarmManager.RTC_WAKEUP, updateTime.getTimeInMillis(), AlarmManager.INTERVAL_FIFTEEN_MINUTES, pendingIntent);

            Log.d("MyActivity", "Set alarmManager.setRepeating to: " + updateTime.getTime().toLocaleString());

      }

}


First create BroadcastReceiver Class
public class MyStartServiceReceiver extends BroadcastReceiver { 
     @Override
     public void onReceive(Context context, Intent intent) {
            Intent dailyUpdater = new Intent(context, MyService.class); 
            context.startService(dailyUpdater);
            Log.d("AlarmReceiver", "Called context.startService from AlarmReceiver.onReceive");
    } 
}

当应用程序关闭或处于后台时，定期从服务器获取数据并在状态栏上显示通知。

创建服务

public class MyService extends IntentService {
    public MyService() {
       super("MyServiceName");
    }
    @Override
    protected void onHandleIntent(Intent intent) {
        Log.d("MyService", "About to execute MyTask");
        new MyTask().execute();
        this.sendNotification(this);
    }
    private class MyTask extends AsyncTask<String, Void, Boolean> {
        @Override 
         protected Boolean doInBackground(String... strings) {
                Log.d("MyService - MyTask", "Calling doInBackground within MyTask");
               return false;
        } 
 }        
private void sendNotification(Context context) {
        Intent notificationIntent = new Intent(context, MainActivity.class);
        PendingIntent contentIntent = PendingIntent.getActivity(context, 0, notificationIntent, 0);
        NotificationManager notificationMgr = (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE);
        Notification notification =  new Notification(android.R.drawable.star_on, "Refresh", System.currentTimeMillis());
        notification.flags |= Notification.FLAG_AUTO_CANCEL;
        notification.setLatestEventInfo(context, "Title","Content", contentIntent);
        notificationMgr.notify(0, notification);
     }
}

别忘了在 AndroidManifest.xml 文件中写下下面几行

<service android:name="MyService" ></service> 
<receiver android:name="MyStartServiceReceiver" ></receiver>