线程和上下文之间的问题 - Android

Question

我正在尝试实现一个线程，以便我可以在后台发送 GPS 坐标。我认为我有一个良好的开端，但我遇到了一些麻烦。哪里写着

locManager = (LocationManager) context.getSystemService(Context.LOCATION_SERVICE);

。

我在上下文中收到错误（在 getSystemService 之前），提示“上下文无法解析”。我从我的主要活动中调用这个类，并使用以下语句

new FindLocation(getBaseContext()).start(usr_id1);

也许这与问题有关。

public class FindLocation extends Thread {

private LocationManager locManager;
private LocationListener locListener;

Context ctx;
public String userId;

public FindLocation(Context ctx) {
     this.ctx = ctx;
}

 public void start(String userId) {
        this.userId = userId;
        super.start();
      }

 @Override
public void run() {
    final String usr = userId;
    
    //get a reference to the LocationManager
    locManager = (LocationManager) context.getSystemService(Context.LOCATION_SERVICE);
   
    //checked to receive updates from the position
    locListener = new LocationListener() {
        public void onLocationChanged(Location loc) {
            
            String lat = String.valueOf(loc.getLatitude()); 
            String lon = String.valueOf(loc.getLongitude());
            
            JSONArray jArray;
            String result = null;
            InputStream is = null;
            StringBuilder sb = null;
            
             ArrayList<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>();
             nameValuePairs.add(new BasicNameValuePair("id", usr));
             
            //http post
            try{
                
                 HttpClient httpclient = new DefaultHttpClient();
                 HttpPost httppost = new HttpPost("http://www.example.com/test/example.php");     
                 httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
                 HttpResponse response = httpclient.execute(httppost);
                 HttpEntity entity = response.getEntity();
                 is = entity.getContent();
                 }catch(Exception e){
                     Log.e("log_tag", "Error in http connection"+e.toString());
                }
            
            //convert response to string
            try{
                  BufferedReader reader = new BufferedReader(new InputStreamReader(is,"iso-8859-1"),8);
                   sb = new StringBuilder();
                   sb.append(reader.readLine() + "\n");
            
                   String line="0";
                   while ((line = reader.readLine()) != null) {
                                  sb.append(line + "\n");
                    }
                    is.close();
                    result=sb.toString();
                    }
            
                    catch(Exception e){
                          Log.e("log_tag", "Error converting result "+e.toString());
                            

                    }
    
            try{
                  jArray = new JSONArray(result);
                  JSONObject json_data=null;
                  for(int i=0;i<jArray.length();i++){
                         json_data = jArray.getJSONObject(i);
                         String ct_name = json_data.getString("phoneID");
                         //stop = true;
                         Log.i("User ID", ct_name);
                         if(ct_name == usr) {
                             locManager.removeUpdates(locListener);
                         }
                         else{
                             Log.i("User ID", "NONE");
                         }
                     } 
                  }
    
                  catch(Exception e){
                        //Log.e("log_tag", "Error converting result "+e.toString());
                        
                        HttpClient httpclient = new DefaultHttpClient();
                        HttpPost httppost = new HttpPost("http://example.com/test/example.php");

                        try {
                               List<NameValuePair> nameValuePairs1 = new ArrayList<NameValuePair>(2);
                               nameValuePairs1.add(new BasicNameValuePair("lat", lat)); 
                               nameValuePairs1.add(new BasicNameValuePair("lon", lon));
                               nameValuePairs1.add(new BasicNameValuePair("id", usr));
                               httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs1));
                               httpclient.execute(httppost);
                               Log.i("SendLocation", "Yes"); 
                         } 
                         catch (ClientProtocolException g) {
                             // TODO Auto-generated catch block
                         } catch (IOException f) {
                            // TODO Auto-generated catch block
                            e.printStackTrace();
                        } 
            } 
        }       
        
        
        public void onProviderDisabled(String provider){
        }
        public void onProviderEnabled(String provider){ 
        }
        public void onStatusChanged(String provider, int status, Bundle extras){
        }
    };
    locManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 6000, 0, locListener);
}
}

Answer 1

    public FindLocation(Context ctx) {
     this.ctx = ctx;
    }

根据您发布的内容，您应该使用

ctx

而不是

context

Answer 2

替换这条线

locManager = (LocationManager) context.getSystemService(Context.LOCATION_SERVICE);

由

locManager = (LocationManager) ctx.getSystemService(Context.LOCATION_SERVICE);