在Android地圖上保存標記App

Question

我正在創建一個Android地圖應用程序，我想在當前位置創建標記並顯示以前的這些標記。我可以在當前位置創建標記，但是當我在其他位置恢復應用時，我的應用只顯示當前位置標記，而不是之前的位置標記。請幫忙。這裏是我的嘗試：

public class Main extends FragmentActivity implements OnMapReadyCallback, GoogleApiClient.ConnectionCallbacks, 
    GoogleApiClient.OnConnectionFailedListener { 

private GoogleMap mMap; 
private GoogleApiClient mGoogleApiClient; 
public Location mLastLocation; 
ArrayList<LatLng> listOfPoints = new ArrayList<>(); 
public boolean isMapReady = false; 

@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main); 

    SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager() 
      .findFragmentById(R.id.map); 
    mapFragment.getMapAsync(this); 

    if (mGoogleApiClient == null) { 
     mGoogleApiClient = new GoogleApiClient.Builder(this) 
       .addConnectionCallbacks(this) 
       .addOnConnectionFailedListener(this) 
       .addApi(LocationServices.API) 
       .build(); 

    } 
} 


public void onMapReady(GoogleMap googleMap) { 
    mMap = googleMap; 
    isMapReady = true; 
} 

public boolean onMarkerClick(final Marker marker) { 
    return false; 
} 

public void onConnected(Bundle connectionHint) { 
    if (ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) { 

     return; 
    } 
    if (ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) { 

     return; 
    } 
    mLastLocation = LocationServices.FusedLocationApi.getLastLocation(
      mGoogleApiClient); 

    MarkerOptions mp = new MarkerOptions(); 
    mp.position(new LatLng(mLastLocation.getLatitude(), mLastLocation.getLongitude())); 

    mp.title("my position"); 

    mMap.addMarker(mp); 

    mMap.animateCamera(CameraUpdateFactory.newLatLngZoom(
      new LatLng(mLastLocation.getLatitude(), mLastLocation.getLongitude()), 16)); 
    LatLng newLatLng = new LatLng(mLastLocation.getLatitude(), mLastLocation.getLongitude()); 
    listOfPoints.add(newLatLng); 


    } 

public void onConnectionSuspended(int i) { 

} 

public void onConnectionFailed(@NonNull ConnectionResult connectionResult) { 

} 

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

protected void onStop() { 
    super.onStop(); 
    mGoogleApiClient.disconnect(); 

} 

protected void onPause() { 
    super.onPause(); 
    try { 
     // Modes: MODE_PRIVATE, MODE_WORLD_READABLE, MODE_WORLD_WRITABLE 
     FileOutputStream output = openFileOutput("latlngpoints.txt", 
       Context.MODE_PRIVATE); 
     DataOutputStream dout = new DataOutputStream(output); 
     dout.writeInt(listOfPoints.size()); // Save line count 
     for (LatLng point : listOfPoints) { 
      dout.writeUTF(point.latitude + "," + point.longitude); 
      Log.v("write", point.latitude + "," + point.longitude); 
     } 
     dout.flush(); // Flush stream ... 
     dout.close(); // ... and close. 
    } catch (IOException exc) { 
     exc.printStackTrace(); 
    } 
} 

protected void onResume(){ 
    super.onResume(); 
    if (isMapReady==true){ 
     try { 
      FileInputStream input = openFileInput("latlngpoints.txt"); 
      DataInputStream din = new DataInputStream(input); 
      int sz = din.readInt(); // Read line count 
      for (int i = 0; i < sz; i++) { 
       String str = din.readUTF(); 
       Log.v("read", str); 
       String[] stringArray = str.split(","); 
       double latitude = Double.parseDouble(stringArray[0]); 
       double longitude = Double.parseDouble(stringArray[1]); 
       listOfPoints.add(new LatLng(latitude, longitude)); 
      } 
      din.close(); 
      loadMarkers(listOfPoints); 
     } catch (IOException exc) { 
      exc.printStackTrace(); 
     } 
    } 
} 
protected void onSaveInstanceState(Bundle outState){ 
    super.onSaveInstanceState(outState); 

    outState.putParcelableArrayList("places", listOfPoints); 
} 
private void restore(Bundle outState){ 
    if (outState != null) { 
     listOfPoints =(ArrayList<LatLng>)outState.getSerializable("places"); 
    } 
} 
protected void onRestoreInstanceState(Bundle outState) { 
    super.onRestoreInstanceState(outState); 
    restore(outState); 
} 
private void loadMarkers(List<LatLng> listOfPoints) { 
    int i=listOfPoints.size(); 
    while(i>0){ 
     i--; 
     double Lat=listOfPoints.get(i).latitude; 
     double Lon=listOfPoints.get(i).longitude; 
     MarkerOptions mp = new MarkerOptions(); 

     mp.position(new LatLng(Lat, Lon)); 

     mp.title("my previous position"); 

     mMap.addMarker(mp); 

     mMap.animateCamera(CameraUpdateFactory.newLatLngZoom(
       new LatLng(Lat, Lon), 16)); 
    } 
} 
} 

Answer 1

注意：

• 的getLastLocation()方法可能，如果沒有以前的位置可返回空值：getLastLocation Documentation
• 最後知道的位置不一定是你的當前位置
• super.onStart(),super.onPause()和super.onStop()應該是您的onStart(),onPause()和中的第一條指令方法。 More infos about Activity Lifecycle and methods overriding

在onPause()方法您在保存文件包含在listOfPoints的位置，但你永遠不添加最後已知位置到該列表。您可能想要在onConnect()方法中添加。

編輯：當你啓動應用程序，調用onCreate()，onStart()和onResume()方法（see Activity Lifecycle）。這意味着，當地圖還沒有準備好時，addMarker()方法可能會被調用。只有在之前調用onMapReady()方法時，您可能需要添加標記。

編輯（因爲你更新的代碼）：

• 使用openFileOutput("latlngpoints.txt", Context.MODE_APPEND)，而不是Context.MODE_PRIVATE
• 你應該從文件中讀取的標記也onMapReady()或onConnected(Bundle connectionHint)就像你在onResume()方法做（因爲當您運行應用程序時，地圖還沒有準備就緒，您將不會執行任何操作，只能在您的onResume()

還要注意，您的文件將可能containt重複