我正在开发一个列出最靠近用户的餐馆的应用程序。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活动到达前台（onResume）时请求更新，以避免不断使用电池。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，它在模拟器上工作正常。
问题： 当我实际改变我的位置（比如5英里以外的车道）并打开我的应用程序和活动以显示最近的餐馆时，需要很长时间（4-5分钟）才能刷新该位置，直到那时应用程序继续显示以前位置的餐馆。但是，如果我实际更改我的位置并访问Google地图然后打开我的餐馆应用程序，那么它会立即生效。我确保GPS已开启。打开活动后，如何让位置管理器启动并刷新位置？ 提前谢谢！
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};
}
}
答案 0 :(得分：9)
您未快速获取更新位置信息的主要原因是您依赖于NETWORK_PROVIDER方法中的RestaurantHelper.getLastKnownLocation()，但是为GPS_PROVIDER注册了LocationListener onCreate()。
所以，RestaurantHelper.getLastKnownLocation()中的代码：
Location location = lm.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
......应改为：
Location location = lm.getLastKnownLocation(LocationManager.GPS_PROVIDER);
理论上，这应该会为您提供最新的GPS位置，当您注册听众时，该位置应该已刷新。相反，您也可以更改为在NETWORK_PROVIDER中收听onCreate()并按原样离开RestaurantHelper.getLastKnownLocation()。这取决于您的准确度要求 - 如果您希望高精度位置将最近的位置返回到最近的建筑物级别（例如，5-30米），则应使用GPS_PROVIDER。但是，如果你能够更准确地使用，NETWORK_PROVIDER通常会比GPS更快地返回一个新位置，特别是如果你在室内，有时如果从WiFi派生，这可能相当准确。
另一种方法是通过在GPS_PROVIDER中通过两条NETWORK_PROVIDER行注册来同时收听requestLocationUpdates()和onCreate()，然后检查以查看最近的时间戳。来自lm.getLastKnownLocation(LocationManager.GPS_PROVIDER);和lm.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);的位置，并使用最近更新的位置。
我还建议您进行以下更改，以使您的代码在大量Android设备上可靠：
requestLocationUpdates() minDistance参数指定为0 - minDistance参数的历史记录是由OEM解释的方式不可靠且不可预测，直到Android 4.1。getLastKnownLocation()方法时，这应该比Android框架位置API更可靠，并且在不同设备上更加一致。请注意，这取决于Google Play Services SDK，该SDK仅适用于Android 2.2及更高版本。答案 1 :(得分：5)
我有2条建议
LocationClient video，是做位置事务的新方法。它对LocationManager进行了改进，可能很难管理和开发。
如果您需要使用LocationManager，您必须知道requestLocationUpdates是错误的（非常错误）。由于它在自定义硬件上的所有实现都不同有一个黑客/解决方案可行。在调用requestLocationUpdates之前，只需使用以下
代码：
HomeScreen.getLocationManager().requestLocationUpdates(
LocationManager.NETWORK_PROVIDER, 0, 0, new LocationListener() {
@Override
public void onStatusChanged(String provider, int status, Bundle extras) {
}
@Override
public void onProviderEnabled(String provider) {
}
@Override
public void onProviderDisabled(String provider) {
}
@Override
public void onLocationChanged(final Location location) {
}
});
答案 2 :(得分：2)
requestLocationUpdates是错误的。始终使用网络提供程序来触发onLocationChanged（...）
locManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 1000, 100, this)
仅在使用网络提供商后才使用gps提供程序背靠背：
locManager.requestLocationUpdates( LocationManager.GPS_PROVIDER, 1000, 100, this)
在通过gps请求位置更新之前，请不要忘记检查gps是否已启用。