Java Android：从json文件获取Google地图位置

我正在开发一个Android应用程序， 我试图从地图上的json显示位置

我很乐意帮忙，谢谢

cities.json：

 [{
    "name": "test1",
    "lat": 31.783306,
    "lng": 34.980238
  },
  {
    "name": "test2",
    "lat": 31.432895,
    "lng": 34.541314
  }]

AlertView.java：

public class AlertView extends AppCompatActivity implements OnMapReadyCallback{
    GoogleMap mMap;

    String mAlertZone;
    String mAlertDateString;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        // Set up UI
        setContentView(R.layout.alert_view);

        // Get map instance
        //mMap = ((SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map)).getMap();

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

    @Override
    public void onMapReady(GoogleMap googleMap) {
        mMap = googleMap;
        // Initialize alert
        unpackExtras();
        // Initialize UI
        initializeUI();
        // Initialize map
        initializeMap();
    }


    void unpackExtras() {
        // Get alert area
        mAlertZone = getIntent().getStringExtra(AlertViewParameters.ALERT_ZONE);

        // Get alert date string
        mAlertDateString = getIntent().getStringExtra(AlertViewParameters.ALERT_DATE_STRING);
    }

    void mapLoadedListener () {
        // Wait for map to load
        mMap.setOnCameraChangeListener(new GoogleMap.OnCameraChangeListener() {
            @Override
            public void onCameraChange(CameraPosition arg0) {
                // Prevent from being called again
                //mMap.setOnCameraChangeListener(null);

                // Fix RTL bug with hebrew
                mMap.setInfoWindowAdapter(new RTLMarkerInfoWindowAdapter(getLayoutInflater()));

                // Show my location button
                //mMap.setMyLocationEnabled(true);

                // Wait for tiles to load
                new Handler().postDelayed(new Runnable() {
                    @Override
                    public void run() {
                        // Add map overlays
                        addOverlays();
                    }
                }, 500);
            }
        });
    }




    void initializeMap() {
        // Get map instance
        if (mMap == null) {
            // Stop execution
            return;
        }

        // Wait for map to load
        addOverlays();
    }
    List<LatLng> values = new ArrayList<LatLng>();
    void addOverlays() {
        // Get alert area
        List<City> cities = LocationData.getCitiesByZone(mAlertZone, this);

        // No cities found?
        if (cities.size() == 0) {
            return;
        }

        // Default to zoom of 8
        int zoom = 8;

        // Default to center of Israel
        LatLng location = new LatLng(31.4117256, 35.0818155);

        // Get user's locale
        boolean isEnglish = Localization.isEnglishLocale(this);

        // Traverse over cities
        for (City city : cities) {
            // No location?
            if (city.latitude == 0) {
                continue;
            }

            // Get name
            String cityName = (isEnglish) ? city.nameEnglish : city.name;

            // Get countdown
            String zoneWithCountdown = LocationData.getLocalizedZoneWithCountdown(city.zone, this);

            // Set title manually after overriding locale
            setTitle(zoneWithCountdown);

            // Set zoom
            zoom = 12;

            // Create location
            location = new LatLng(city.latitude, city.longitude);
            values.add(location); //this adds an element to the list.

            // Optional snippet
            String snippet = null;

            // Add shelter count if exists for this city
            //if (city.shelters > 0) {
            //snippet = getString(R.string.lifeshieldShelters) + " " + city.shelters;
            //}

            // Add marker to map
            mMap.addMarker(new MarkerOptions()
                    .position(location)
                    .title(cityName)
                    .snippet(snippet));
        }

        // Prepare new camera position
        CameraPosition position = new CameraPosition.Builder()
                .target(location)
                .zoom(zoom)
                .tilt(30)
                .bearing(10)
                .build();

        // Animate nicely
        mMap.animateCamera(CameraUpdateFactory.newCameraPosition(position), 1500, null);

        aa();
    }
    void aa() {
        if (values.size() > 1) {
            LatLngBounds.Builder builder = new LatLngBounds.Builder();
            for (LatLng c : values) {
                builder.include(c);
            }
            LatLngBounds bounds = builder.build();
            float zoomLevel = 16.0f; //This goes up to 21 // offset from edges of the map in pixels
            CameraUpdate cu = CameraUpdateFactory.newLatLngBounds(bounds, 320);
            mMap.animateCamera(cu);
        }
    }
    @Override
    public boolean onCreateOptionsMenu(Menu OptionsMenu) {
        // Add share button
        initializeShareButton(OptionsMenu);

        // Show the menu
        return true;
    }

    private String getShareMessage() {
        // Get zone name
        String zone = LocationData.getLocalizedZone(mAlertZone, this);

        // Construct share message
        return getString(R.string.alertSoundedAt) + " " + zone + " (" + LocationData.getCityNamesByZone(mAlertZone, this) + ") " + getString(R.string.atTime) + " " + mAlertDateString + " " + getString(R.string.alertSentVia);
    }

    void initializeShareButton(Menu OptionsMenu) {
        // Add refresh in Action Bar
        MenuItem shareItem = OptionsMenu.add(Menu.NONE, Menu.NONE, Menu.NONE, getString(R.string.shareAlert));

        // Set up the view
        shareItem.setIcon(R.drawable.ic_share);

        // Specify the show flags
        MenuItemCompat.setShowAsAction(shareItem, MenuItem.SHOW_AS_ACTION_ALWAYS);

        // On click, open share
        shareItem.setOnMenuItemClickListener(new MenuItem.OnMenuItemClickListener() {
            @Override
            public boolean onMenuItemClick(MenuItem item) {
                // Prepare share intent
                Intent shareIntent = new Intent(Intent.ACTION_SEND);

                // Set as text/plain
                shareIntent.setType("text/plain");

                // Add text
                shareIntent.putExtra(Intent.EXTRA_TEXT, getShareMessage());

                // Show chooser
                startActivity(Intent.createChooser(shareIntent, getString(R.string.shareAlert)));

                // Consume event
                return true;
            }
        });
    }

    public boolean onOptionsItemSelected(final MenuItem Item) {
        // Check item ID
        switch (Item.getItemId()) {
            // Home button?
            case android.R.id.home:
                onBackPressed();
        }

        return super.onOptionsItemSelected(Item);
    }

    @Override
    protected void onResume() {
        super.onResume();

        // Support for RTL languages
        RTLSupport.mirrorActionBar(this);

        // Clear notifications and stop sound from playing
        AppNotifications.clearAll(this);
    }

    @Override
    public void onConfigurationChanged(android.content.res.Configuration newConfig) {
        super.onConfigurationChanged(newConfig);

        // Support for RTL languages
        RTLSupport.mirrorActionBar(this);
    }

    void initializeUI() {
        // Reset activity name (after localization is loaded)
        setTitle(R.string.appName);

        // Allow click on home button
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);

        // RTL action bar hack
        RTLSupport.mirrorActionBar(this);



    }

}

---

我尝试了一些方法，但当我打开地图时，它会在不同于json文件中写入的位置打开它。

首先，您应该使用LatLng对象 像

如果您决定不这样做，那么至少应该在城市类中使用纬度和经度的双值

public class LocationData {
    private static List<City> mCities;

public static List<City> getAllCities(Context context) {
        // Got it in cache?
        if (mCities != null) {
            return mCities;
        }

        // Initialize the list
        mCities = new ArrayList<>();

        try {
            // Open the cities.json for reading
            InputStream stream = context.getResources().openRawResource(R.raw.cities);

            // Create a buffered reader
            BufferedReader reader = new BufferedReader(new InputStreamReader(stream));

            // StringBuilder for efficiency
            StringBuilder builder = new StringBuilder();

            // A temporary variable to store current line
            String currentLine;

            // Read all lines
            while ((currentLine = reader.readLine()) != null) {
                // Append to builder
                builder.append(currentLine);
            }

            // Convert to string
            String json = builder.toString();

            // Convert to city objects
            mCities = Singleton.getJackson().readValue(json, new TypeReference<List<City>>() {
            });
        }
        catch (Exception exc) {
            // Log it
            Log.e(Logging.TAG, "Failed to load cities.json", exc);
        }

        // Return them
        return mCities;
    }
}

public class City {
    @JsonProperty("lat")
    public int latitude;

    @JsonProperty("lng")
    public int longitude;

    @JsonProperty("name")
    public String name;

    @Override
    public String toString() {
        return value;
    }
}

new LatLng(latitude.doubleValue(), longtitude.doubleValue());