Android locationManager requestLocationUpdates 不起作用

Question

我正在开发一个列出离用户最近的餐馆的应用程序。单击刷新按钮时，它会列出用户当前位置的餐馆。我正在使用位置管理器并仅在 Activity 进入前台(onResume)时请求更新以避免电池的持续使用。当应用程序进入 onPause() 时，位置更新将停止。当我通过终端传递更新时，它在模拟器上运行良好。

问题:当我实际更改我的位置(比如开车 5 英里)并打开我的应用程序和显示最近的餐馆的 Activity 时，刷新位置需要很长时间(4-5 分钟)，直到那时应用程序继续显示以前位置的餐厅。但是，如果我实际更改位置并访问 Google map ，然后打开我的餐厅应用程序，那么它会立即生效。我已确保 GPS 已打开。我该怎么做才能让位置管理器在我打开 Activity 后立即启动并刷新位置？提前致谢!

package com.mortley.android.restaurantsaver;

public class NearbyRestaurantActivity extends ListActivity implements OnClickListener, LocationListener{
    private Button refreshButton, searchRestaurants; 
    ImageButton goToSearch;
    private double[] lastKnownLocation;
    private EditText locationEditText;
    private LocationManager locManager;
    private LocationListener locListener;
    private boolean gps_enabled = false;
    private boolean network_enabled = false;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.nearbyrestaurants);
        refreshButton = (Button)findViewById(R.id.reloadButton);
        refreshButton.setOnClickListener(this);

        searchRestaurants = (Button)findViewById(R.id.searchButton);
        searchRestaurants.setOnClickListener(this);
        goToSearch = (ImageButton)findViewById(R.id.goLocationButton);
        goToSearch.setOnClickListener(this);
        locationEditText = (EditText)findViewById(R.id.addressTextBox);
        locationEditText.setVisibility(View.GONE);
        goToSearch.setVisibility(View.GONE);

        locManager = (LocationManager) this.getSystemService(Context.LOCATION_SERVICE);//??


        locManager.requestLocationUpdates( LocationManager.GPS_PROVIDER, 1000, 100, this);

        //checks network connectivity
        boolean checkConnection = isNetworkAvailable();
        if(!checkConnection){
            Toast.makeText(getApplicationContext(), "Check your Network Connectivity", Toast.LENGTH_LONG).show();
        }

        if(checkConnection){
            //sets current location parameters for the user
            lastKnownLocation = RestaurantHelper.getLastKnownLocation(this);
            //Log.v("NearbyRestaurantActivity", "This"+this);

            RestaurantApplication application = (RestaurantApplication) this.getApplication();
            RestaurantAdapter restaurantAdapter = new RestaurantAdapter(this, R.layout.restaurantrow,  R.id.label,new ArrayList<RestaurantReference>());
            restaurantAdapter.setLastKnownLocation(lastKnownLocation);  


            //set a global variable for the RestaurantAdapter in the RestaurantApplication class.
            application.setRestaurantAdapter(restaurantAdapter);
            //Set the adapter first and then update it when the RestaurantHttpAsyncTask makes a web service call.
            setListAdapter(restaurantAdapter);
            //Make a webservice call in a different thread passing Keyword for URL as a string array.
            RestaurantHttpAsyncTask m_progressTask;
            String[] keywords = {"", "american", "asian", "italian","mexican"};
            //String[] keywords = {"indian"};
            m_progressTask = new RestaurantHttpAsyncTask(NearbyRestaurantActivity.this, keywords);
            m_progressTask.setRestaurantAdapter(restaurantAdapter);
            m_progressTask.execute();
        }
    }

    @Override
    public void onClick(View v) {   
        //Refresh button helps to refresh the restaurant list on location change. Again it makes a call to the webservice using Async Task
        if(v.getId() == refreshButton.getId() ){


            try {
                gps_enabled = locManager.isProviderEnabled(LocationManager.GPS_PROVIDER);
            } catch (Exception ex) {
                ex.printStackTrace();
            }
            try {
                network_enabled = locManager.isProviderEnabled(LocationManager.NETWORK_PROVIDER);
            } catch (Exception ex) {
                ex.printStackTrace();
            }

            // don't start listeners if no provider is enabled
            if (!gps_enabled && !network_enabled) {
                Toast.makeText(getApplicationContext(), "Sorry, Location is not determined. Please enable your Network Providers.", Toast.LENGTH_LONG).show();


            }

            //check network connectivity before refresh
            boolean checkConnection = isNetworkAvailable();
            if(!checkConnection){
                Toast.makeText(getApplicationContext(), "Check your Network Connectivity", Toast.LENGTH_LONG).show();
            }
            if(checkConnection){

                RestaurantApplication application = (RestaurantApplication) this.getApplication();
                RestaurantAdapter restaurantAdapter = new RestaurantAdapter(this, R.layout.restaurantrow,  R.id.label, new ArrayList<RestaurantReference>());
                restaurantAdapter.setLastKnownLocation(lastKnownLocation);  
                //set a global variable for the RestaurantAdapter in the RestaurantApplication class.
                application.setRestaurantAdapter(restaurantAdapter);
                //Set the adapter first and then update it when the RestaurantHttpAsyncTask makes a web service call.
                setListAdapter(restaurantAdapter);
                //Make a webservice call in a different thread passing Keyword for URL as a string array.
                RestaurantHttpAsyncTask m_progressTask, m_progressTask1;
                String[] keywords = {"", "american", "asian", "italian","mexican", "chinese", "indian"};
                //String[] keywords = {"Chinese"};
                m_progressTask = new RestaurantHttpAsyncTask(NearbyRestaurantActivity.this, keywords);
                m_progressTask.setRestaurantAdapter(restaurantAdapter);
                m_progressTask.execute();
            }
        }

        if(v.getId() == goToSearch.getId() ){

            Activity child = this;
            while(child.getParent() != null){
                child = child.getParent();
            }
            TabGroup1Activity parent = (TabGroup1Activity)getParent();


            InputMethodManager imm = (InputMethodManager)getSystemService(
                    Context.INPUT_METHOD_SERVICE);
            imm.hideSoftInputFromWindow(locationEditText.getWindowToken(), InputMethodManager.HIDE_NOT_ALWAYS);

            //changes ** restaurantAdapter to RestaurantAdapter1 to test & application to application1  
            RestaurantApplication application1 = (RestaurantApplication) this.getApplication();
            RestaurantAdapter restaurantAdapter1 = new RestaurantAdapter(this, R.layout.restaurantrow,  R.id.label, new ArrayList<RestaurantReference>());
            restaurantAdapter1.setLastKnownLocation(lastKnownLocation);  
            //set a global variable for the RestaurantAdapter in the RestaurantApplication class.
            application1.setRestaurantAdapter(restaurantAdapter1);
            //Set the adapter first and then update it when the RestaurantHttpAsyncTask makes a web service call.
            setListAdapter(restaurantAdapter1);
            //Make a webservice call in a different thread passing Keyword for URL as a string array.
            RestaurantHttpAsyncTaskTextSearch m_progressTask, m_progressTask1;
            String keywords = locationEditText.getText().toString();
            if(keywords.equals("")){
                keywords = "Pizza in Palo Alto";
            }
            keywords = keywords.replaceAll(" ", "%20");
            keywords = keywords.replaceAll(",", "%20");
            m_progressTask = new RestaurantHttpAsyncTaskTextSearch (NearbyRestaurantActivity.this, keywords);
            m_progressTask.setRestaurantAdapter(restaurantAdapter1);
            m_progressTask.execute();

            locationEditText.setVisibility(View.GONE);
            goToSearch.setVisibility(View.GONE);
        }
        if(v.getId() == searchRestaurants.getId() ){
            if(goToSearch.isShown() == true){
                goToSearch.setVisibility(View.GONE);
                locationEditText.setVisibility(View.GONE);
            }
            else if(goToSearch.isShown() == false){
                //check network connectivity before refresh
                boolean checkConnection = isNetworkAvailable();
                if(!checkConnection){
                    Toast.makeText(getApplicationContext(), "Check your Network Connectivity", Toast.LENGTH_LONG).show();
                }
                if(checkConnection){
                    goToSearch.setVisibility(View.VISIBLE);
                    locationEditText.setVisibility(View.VISIBLE);

                }
            }
        }

    }
    //Method to check network connectivity
    public boolean isNetworkAvailable() {
        ConnectivityManager connectivityManager 
        = (ConnectivityManager)getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo activeNetworkInfo = connectivityManager.getActiveNetworkInfo();
        if (activeNetworkInfo != null && activeNetworkInfo.isConnectedOrConnecting()) {
            //Log.d("network", "Network available:true");
            return true;
        } else {
            //Log.d("network", "Network available:false");
            return false;
        }
    }

    @Override
    protected void onResume() {
        super.onResume();
        locManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 50, 100, this); 
        //Log.v("NearbyRestaurantActivity", "In OnResume()");
    }

    @Override
    protected void onPause() {
        super.onPause();
        locManager.removeUpdates(this); 
        //Log.v("NearbyRestaurantActivity", "In onPause()");

    }

    @Override
    public void onLocationChanged(Location location) {
        // TODO Auto-generated method stub

    }

    @Override
    public void onProviderDisabled(String provider) {
        // TODO Auto-generated method stub

    }

    @Override
    public void onProviderEnabled(String provider) {
        // TODO Auto-generated method stub

    }

    @Override
    public void onStatusChanged(String provider, int status, Bundle extras) {
        // TODO Auto-generated method stub

    }
}






public class RestaurantHelper {

public static double[] getLastKnownLocation(Activity activity){
    double lat = 0.0;
    double lon = 0.0;
    LocationManager lm = (LocationManager) activity.getSystemService(Context.LOCATION_SERVICE);    
    Location location = lm.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);  

    if(location == null){
        lat = 0.0;
        lon = 0.0;
    }
    else{
        //Log.v("Latitude", Double.toString(location.getLatitude()));
        //Log.v("Longitude", Double.toString(location.getLongitude()));

        lat = location.getLatitude();
        lon = location.getLongitude();
    }
    return new double[]{lat,lon};
}
}

Answer 1

您无法快速获取更新位置信息的主要原因是您依赖 NETWORK_PROVIDER在RestaurantHelper.getLastKnownLocation()方法，但为 GPS_PROVIDER 注册一个 LocationListener在 onCreate() .

因此，RestaurantHelper.getLastKnownLocation() 中的这段代码:

Location location = lm.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);

...应该改为:

Location location = lm.getLastKnownLocation(LocationManager.GPS_PROVIDER);

理论上，这应该会为您提供最新的 GPS 位置，该位置应该在您注册监听器时刷新。相反，您也可以改为收听NETWORK_PROVIDER。在 onCreate()然后离开RestaurantHelper.getLastKnownLocation()原样。这取决于您的精度要求 - 如果您希望高精度位置返回最近的位置到最近的建筑物水平(例如，5-30m)，您应该使用 GPS_PROVIDER .但是，如果您可以接受较粗略的精度，NETWORK_PROVIDER通常返回新位置的速度比 GPS 快得多，尤其是当您在室内时，有时如果从 WiFi 中获取，这可能相当准确。

另一种方法是同时收听 GPS_PROVIDER和 NETWORK_PROVIDER通过两个 requestLocationUpdates() 注册onCreate() 中的行，然后查看来自 lm.getLastKnownLocation(LocationManager.GPS_PROVIDER); 的 Location 上的最新时间戳和 lm.getLastKnownLocation(LocationManager.NETWORK_PROVIDER); ，并使用最近更新的那个。

我还建议进行以下更改，以使您的代码在大量 Android 设备上可靠:

1. 指定requestLocationUpdates() minDistance参数为 0在监听 GPS 或网络位置更新时 - 在 Android 4.1 之前，minDistance 参数在 OEM 解释它的方式上一直是不可靠和不可预测的。
2. 切换到新的 Fused Location Provider - 这在调用 getLastKnownLocation() 时应该更可靠方法比 Android 框架位置 API，并且在不同设备之间更一致。请注意，这依赖于 Google Play Services SDK，它仅适用于 Android 2.2 及更高版本。