Question

我有一个关于如何做一个我认为简单的项目的问题。接下来我有一个应用程序，将手机的位置发送10秒到MySql，好吧。

但我现在只需要在另一个应用程序中显示这些用户在映射的10秒内的当前位置，而无需打开和关闭活动。

在下面的代码中，显示了使用json来自Mysql库的标记的映射。有什么提示吗？

   public class MainActivity extends FragmentActivity {

    // Google Map
    private GoogleMap googleMap;

    // Latitude & Longitude
    private Double Latitude = 0.00;
    private Double Longitude = 0.00;

    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        //*** Permission StrictMode
        if (android.os.Build.VERSION.SDK_INT > 9) {
            StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
            StrictMode.setThreadPolicy(policy);
        }

        ArrayList<HashMap<String, String>> location = null;
        String url = "http://192.168.1.202/android/getLatLon.php";
        try {

            JSONArray data = new JSONArray(getHttpGet(url));

            location = new ArrayList<HashMap<String, String>>();
            HashMap<String, String> map;

            for(int i = 0; i < data.length(); i++){
                JSONObject c = data.getJSONObject(i);

                map = new HashMap<String, String>();
                map.put("LocationID", c.getString("LocationID"));
                map.put("Latitude", c.getString("Latitude"));
                map.put("Longitude", c.getString("Longitude"));
                map.put("LocationName", c.getString("LocationName"));
                location.add(map);

            }           

        } catch (JSONException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }


        // *** Display Google Map
        googleMap = ((SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.googleMap)).getMap();

        // *** Focus & Zoom
        Latitude = Double.parseDouble(location.get(0).get("Latitude").toString());
        Longitude = Double.parseDouble(location.get(0).get("Longitude").toString());
        LatLng coordinate = new LatLng(Latitude, Longitude);
        googleMap.setMapType(com.google.android.gms.maps.GoogleMap.MAP_TYPE_HYBRID);
        googleMap.animateCamera(CameraUpdateFactory.newLatLngZoom(coordinate, 17));

        // *** Marker (Loop)
        for (int i = 0; i < location.size(); i++) {
            Latitude = Double.parseDouble(location.get(i).get("Latitude").toString());
            Longitude = Double.parseDouble(location.get(i).get("Longitude").toString());
            String name = location.get(i).get("LocationName").toString();
            MarkerOptions marker = new MarkerOptions().position(new LatLng(Latitude, Longitude)).title(name);
            googleMap.addMarker(marker);
        }

    }

    public static String getHttpGet(String url) {
        StringBuilder str = new StringBuilder();
        HttpClient client = new DefaultHttpClient();
        HttpGet httpGet = new HttpGet(url);
        try {
            HttpResponse response = client.execute(httpGet);
            StatusLine statusLine = response.getStatusLine();
            int statusCode = statusLine.getStatusCode();
            if (statusCode == 200) { // Download OK
                HttpEntity entity = response.getEntity();
                InputStream content = entity.getContent();
                BufferedReader reader = new BufferedReader(new InputStreamReader(content));
                String line;
                while ((line = reader.readLine()) != null) {
                    str.append(line);
                }
            } else {
                Log.e("Log", "Failed to download result..");
            }
        } catch (ClientProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return str.toString();
    }

}

Answer 1

您可以使用 COUNTDOWN TIMER ，COUNT DOWN TIMER EXAMPLE，这样每10秒就会发出一次网络请求，您将获得更新后的值。并且您可以使用新的 LATITUDE，LONGITUDE 值更新标记。并且请记住仅在第一个网络请求之后添加标记不需要添加标记只需要更改标记位置。。how to change marker position

但是我会推荐你每次（每10秒）发出一次网络请求并不是一个好主意。自一小时以来，用户可能无法更改位置。因此，它无需API调用。所以如果你使用REAL TIME DATABASE（比如Firebase实时数据库）会更好。并在您的数据库值更新时监听您的数据更改，它将通知您。 Firebase Real time DB Doc reference

Answer 2

如果您想在某段时间内更新地图而无需打开和关闭活动。您应该从onCreate()方法移动逻辑。

Thread myLoopingThread = new Thread(new Runnable() {
    @Override
    public void run() {
        while(!Thread.currentThread().isInterrupted()){
            final String result = getHttpGet("http://192.168.1.202/android/getLatLon.php");
            runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    UpdateMap(result);
                }
            });
            Thread.sleep(timeToSleep);
        }
    }
});

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    //do other stuff..
    myLoopingThread.start();
}
//also we should stop the thread when its not needed anymore
@Override
 protected void onDestroy(){
    myLoopingThread.interrupt();
    super.onDestroy();
}  
void UpdateMap(String input){
    ArrayList<HashMap<String, String>> location = null;

    try {

        JSONArray data = new JSONArray(input);

        location = new ArrayList<HashMap<String, String>>();
        HashMap<String, String> map;

        for(int i = 0; i < data.length(); i++){
            JSONObject c = data.getJSONObject(i);

            map = new HashMap<String, String>();
            map.put("LocationID", c.getString("LocationID"));
            map.put("Latitude", c.getString("Latitude"));
            map.put("Longitude", c.getString("Longitude"));
            map.put("LocationName", c.getString("LocationName"));
            location.add(map);

        }           

    } catch (JSONException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }


    // *** Display Google Map
    googleMap = ((SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.googleMap)).getMap();

    // *** Focus & Zoom
    Latitude = Double.parseDouble(location.get(0).get("Latitude").toString());
    Longitude = Double.parseDouble(location.get(0).get("Longitude").toString());
    LatLng coordinate = new LatLng(Latitude, Longitude);
    googleMap.setMapType(com.google.android.gms.maps.GoogleMap.MAP_TYPE_HYBRID);
    googleMap.animateCamera(CameraUpdateFactory.newLatLngZoom(coordinate, 17));

    // *** Marker (Loop)
    for (int i = 0; i < location.size(); i++) {
        Latitude = Double.parseDouble(location.get(i).get("Latitude").toString());
        Longitude = Double.parseDouble(location.get(i).get("Longitude").toString());
        String name = location.get(i).get("LocationName").toString();
        MarkerOptions marker = new MarkerOptions().position(new LatLng(Latitude, Longitude)).title(name);
        googleMap.addMarker(marker);
    }
}

更新地图上的标记位置，而无需打开和关闭活动

2 个答案: