我正在开发一个列出最接近用户的餐厅的应用程序.当点击刷新按钮时,它会列出用户当前位置的餐馆.我正在使用位置管理器,只有当活动进入前台(onResume)才能请求更新,以避免电池的不断使用.当应用程序进入onPause()时,位置更新被停止.当我通过终端传递更新时,它在模拟器上工作正常.
问题：
当我改变我的位置(比如开车5英里远)时,我打开我的应用程序和活动来显示最近的餐厅,需要很长时间(4-5分钟)的位置刷新,直到应用程序继续显示以前的位置的餐厅.但是,如果我实际更改我的位置并访问Google地图,然后打开我的餐厅应用程序,那么它可以立即工作.我确保GPS被打开.一旦我打开我的活动,我可以做什么来让位置管理员踢和更新位置？
先谢谢你！
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(),Toast.LENGTH_LONG).show();
}
if(checkConnection){
RestaurantApplication application = (RestaurantApplication) this.getApplication();
RestaurantAdapter restaurantAdapter = new RestaurantAdapter(this,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 = {"","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,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(),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,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};
}
}
解决方法
您没有快速获取更新的位置信息的主要原因是您依赖于RestaurantHelper.getLastKNownLocation()方法中的NETWORK_PROVIDER,但在onCreate()中注册了GPS_PROVIDER的LocationListener.
所以,这个代码在RestaurantHelper.getLastKNownLocation()中：
Location location = lm.getLastKNownLocation(LocationManager.NETWORK_PROVIDER);
应该改为：
Location location = lm.getLastKNownLocation(LocationManager.GPS_PROVIDER);
在理论上,这应该给你最新的GPS位置,当你注册听众时应该刷新它.相反,您也可以更改为监听onCreate()中的NETWORK_PROVIDER,并将RestaurantHelper.getLastKNownLocation()保持原样.这取决于您的准确性要求 – 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,如果您可以以更准确的方式生活,NETWORK_PROVIDER通常会返回一个比GPS更快的新位置,特别是如果您在室内,有时如果从WiFi导出,这可能相当准确.
另一种方法是通过在onCreate()中通过两个requestLocationUpdates()行注册来监听GPS_PROVIDER和NETWORK_PROVIDER,然后检查从lm.getLastKNownLocation(LocationManager.GPS_PROVIDER)的位置上查看最近的时间戳.和lm.getLastKNownLocation(LocationManager.NETWORK_PROVIDER);并使用最近更新的那个.
我还建议您进行以下更改,使您的代码在大量Android设备上可靠：
>在侦听GPS或NETWORK位置更新时,将requestLocationUpdates()mindistance参数指定为0 – mindistance参数具有由原始设备制造商解释的方式不可靠和不可预测的历史,直到Android 4.1.
>切换到新的Fused Location Provider – 当调用getLastKNownLocation()方法比Android框架的位置API更为可靠,并且在不同的设备之间更一致.请注意,这依赖于Google Play服务SDK(仅适用于Android 2.2及更高版本).
