在應用啓動時獲取位置地址

Question

我需要應用啓動時的位置。我跟隨這個tut withlocallocationapi得到LastLocation：https://developer.android.com/training/location/retrieve-current.html

當查詢地址的AsyncTask通過一個按鈕執行，但當我把相同的片段放在oncreate或onstart，然後獲得NPE，它可能是完美的定位修復需要很長時間。

我想要加載活動，顯示ProgressBar &然後顯示位置，而不必點擊按鈕。

解決方法是在onstart短暫延遲後執行AsyncTask，但我猜測應該有更高效的東西。

public class MainActivity extends ActionBarActivity implements 
    ConnectionCallbacks, OnConnectionFailedListener{ 


protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main); 
    mAddress = (TextView) findViewById(R.id.address); 
    mActivityIndicator = 
      (ProgressBar) findViewById(R.id.address_progress); 

    buildGoogleApiClient(); 
} 

protected synchronized void buildGoogleApiClient() { 
    mGoogleApiClient = new GoogleApiClient.Builder(this) 
      .addConnectionCallbacks(this) 
      .addOnConnectionFailedListener(this) 
      .addApi(LocationServices.API) 
      .build(); 
} 


@Override 
protected void onStart() { 
    super.onStart(); 
    mGoogleApiClient.connect(); 
} 

@Override 
protected void onStop() { 
    super.onStop(); 
    if (mGoogleApiClient.isConnected()) { 
     mGoogleApiClient.disconnect(); 
    } 
} 

public void onConnected(Bundle connectionHint) { 
    mLastLocation = LocationServices.FusedLocationApi.getLastLocation(mGoogleApiClient); 
} 

private class GetAddressTask extends AsyncTask<Location, Void, String> 
{ 
    Context mContext; 
    public GetAddressTask(Context context) { 
     super(); 
     mContext = context; 
    } 
    @Override 
    protected String doInBackground(Location... params) { 
     Geocoder geocoder = 
       new Geocoder(mContext, Locale.getDefault()); 
     // Get the current location from the input parameter list 
     Location loc = params[0]; 
     // Create a list to contain the result address 
     List<Address> addresses = null; 
     try { 
      addresses = geocoder.getFromLocation(loc.getLatitude(), 
        loc.getLongitude(), 1); 
     } catch (IOException e1) { 
      Log.e("LocationSampleActivity", 
        "IO Exception in getFromLocation()"); 
      e1.printStackTrace(); 
      return ("IO Exception trying to get address"); 
     } catch (IllegalArgumentException e2) { 
      // Error message to post in the log 
      String errorString = "Illegal arguments " + 
        Double.toString(loc.getLatitude()) + 
        " , " + 
        Double.toString(loc.getLongitude()) + 
        " passed to address service"; 
      Log.e("LocationSampleActivity", errorString); 
      e2.printStackTrace(); 
      return errorString; 
     } 
     // If the reverse geocode returned an address 
     if (addresses != null && addresses.size() > 0) { 
      // Get the first address 
      Address address = addresses.get(0); 
      /* 
      * Format the first line of address (if available), 
      * city, and country name. 
      */ 
      String addressText = String.format(
        "%s, %s, %s", 
        // If there's a street address, add it 
        address.getMaxAddressLineIndex() > 0 ? 
          address.getAddressLine(0) : "", 
        // Locality is usually a city 
        address.getLocality(), 
        // The country of the address 
        address.getCountryName()); 
      // Return the text 
      return addressText; 
     } else { 
      return "No address found"; 
     } 
    } 

    @Override 
    protected void onPostExecute(String address) { 
     // Set activity indicator visibility to "gone" 
     mActivityIndicator.setVisibility(View.GONE); 
     // Display the results of the lookup. 
     mAddress.setText(address); 
    } 
} 

public void getAddress(View v) { 
    // Ensure that a Geocoder services is available 
    if (Build.VERSION.SDK_INT >= 
      Build.VERSION_CODES.GINGERBREAD 
      && 
      Geocoder.isPresent()) { 
     // Show the activity indicator 
     mActivityIndicator.setVisibility(View.VISIBLE); 
     /* 
     * Reverse geocoding is long-running and synchronous. 
     * Run it on a background thread. 
     * Pass the current location to the background task. 
     * When the task finishes, 
     * onPostExecute() displays the address. 
     */ 
     (new GetAddressTask(this)).execute(mLastLocation); 
    } 
} 

Answer 1

除非GoogleApiClient處於連接狀態，否則API調用將失敗。您請求它在onStart中連接並且它是異步連接的。你顯然不應該在onStart中放置一個隨機延遲，而且你不應該在AsyncTask中這樣做，因爲這將是片狀的。

在發生onConnected回調時（或之後）發起您的API調用。也許使用條件邏輯，這樣如果您的應用程序恢復，則不會再次進行呼叫。

Answer 2

既然這是一個直接的答案，我會在這裏發表。

簡而言之：請看看我的要點

https://gist.github.com/2022a4d2c21d73f042eb

釋：

GoogleApiClient成功連接到谷歌的服務後，它不能獲得一眨不眨的完整信息，您應該意識到這一點。所以基本上，您會希望向您要使用的API（FuseLocation API，Google Fit API ...）發出請求。而onConnected（）方法是您開始請求的地方。 GoogleAPIClient爲您提供的每個API都將以自己的方式實現回調，您也應該查看文檔。所以請考慮看看我的要點，並提供反饋，如果它的工作。

Answer 3

執行下列操作（順便說一句，我試圖以正確的格式輸入代碼，但它不會採取很抱歉，如果下面看起來邋遢）：

1. 在的onCreate，請設置您GoogleApiClient ：

   mGoogleApiClient = new GoogleApiClient.Builder(this) 
        .addConnectionCallbacks(this) 
        .addOnConnectionFailedListener(this) 
        .addApi(LocationServices.API) 
        .build(); 
   
   mLocationRequest = LocationRequest.create() 
        .setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY) 
        .setInterval(10000).setFastestInterval(5000); 
   

2. 處理通信/的onResume，連接到您的GoogleApiClient：

   mGoogleApiClient.connect（）;

3. 在的onPause，從GoogleApiClient斷開：

   if (mGoogleApiClient.isConnected()) { 
       LocationServices.FusedLocationApi.removeLocationUpdates(mGoogleApiClient, this); 
       mGoogleApiClient.disconnect(); 
   } 
   

4. 在的onConnect回調方法，執行以下操作：

   LocationServices.FusedLocationApi.requestLocationUpdates（mGoogleApiClient，mLocationRequest，FragmentPostActivity。這個）;

5. 在onLocationChanged，讓你的位置，然後斷開：

   公共無效onLocationChanged（位置定位）{

   mLastLocation = location; 
   if (mGoogleApiClient.isConnected() && mLastLocation != null) { 
       Log.e("LocationChanged", String.valueOf(location.getLatitude()) + " Longitude: " + String.valueOf(location.getLongitude())); 
       LocationServices.FusedLocationApi.removeLocationUpdates(mGoogleApiClient, this); 
       mGoogleApiClient.disconnect(); 
   } 
   

   }