如何先显示地图再下载图像标记？

Question

我正在尝试显示 custom marker with images 这里的图片是从互联网上下载的。

一切都很好，得到了预期的结果。

这是输出图像

但是在这里显示地图要花很多时间它是下载图像然后显示地图。有什么办法先显示maps然后下载图片设置markers.

这是我试过的代码

 @Override
public void onMapReady(GoogleMap googleMap) {
    mMap = googleMap;
    MapsInitializer.initialize(this);

    LocationManager locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);
    Criteria criteria = new Criteria();
    assert locationManager != null;
    String provider = locationManager.getBestProvider(criteria, true);
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
        if (ActivityCompat.checkSelfPermission(this,
                Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED
                && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
            requestPermissions(new String[]{
                    Manifest.permission.ACCESS_FINE_LOCATION,
                    Manifest.permission.ACCESS_COARSE_LOCATION
            }, LOCATION_REQUEST_CODE);
            return;
        }
    }
    mLastLocation = locationManager.getLastKnownLocation(provider);

    userLatLng = new LatLng(mLastLocation.getLatitude(), mLastLocation.getLongitude());

    mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(userLatLng, 14.0f));
    mMap.setMyLocationEnabled(true);
    mMap.getUiSettings().setZoomControlsEnabled(true);
    mMap.setBuildingsEnabled(true);
    try {
        bussinessBitmap = new AddMarkers(imgUrl2).execute().get();
    } catch (InterruptedException e) {
        e.printStackTrace();
    } catch (ExecutionException e) {
        e.printStackTrace();
    }
    if (bussinessLatLng != null) {
        bussinessMarker = mMap.addMarker(new MarkerOptions()
                .position(bussinessLatLng)
                .title(businessUser)
                .snippet(getLocation(bussinessLatLng))
                .icon(BitmapDescriptorFactory.fromBitmap(getMarkerBitmapFromView(bussinessBitmap))));
    } else {
        bussinessMarker = mMap.addMarker(new MarkerOptions()
                .position(bussinessLatLng)
                .title(businessUser)
                .snippet(getLocation(bussinessLatLng)));
    }

    try {
        userBitmap = new AddMarkers(imgUrl).execute().get();
    } catch (InterruptedException e) {
        e.printStackTrace();
    } catch (ExecutionException e) {
        e.printStackTrace();
    }
    if (mLastLocation != null) {
        if (userBitmap != null) {
            userMarker = mMap.addMarker(new MarkerOptions().position(userLatLng)
                    .title(username)
                    .snippet(getLocation(userLatLng))
                    .icon(BitmapDescriptorFactory.fromBitmap(getMarkerBitmapFromView(userBitmap))));
        } else {
            userMarker = mMap.addMarker(new MarkerOptions().position(userLatLng)
                    .title(username)
                    .snippet(getLocation(userLatLng)));
        }
    }

    if(!(userLatLng == null || bussinessLatLng == null)) {

        Polyline distanceLine = mMap.addPolyline(new PolylineOptions().add(userLatLng, bussinessLatLng).width(4).color(Color.GREEN));
    }
}

我正在使用 asynctask 下载图片，这里是下载图片的代码

public AddMarkers(String imgUrl) {
        this.imgUrl = imgUrl;
    }

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        pd = new ProgressDialog(MapsActivity.this);
        pd.setTitle("Loading");
        pd.setMessage("Please wait..");
        pd.show();
    }

    @Override
    protected Bitmap doInBackground(Void... voids) {

        URL url;
        try {
            url = new URL(imgUrl);
            return BitmapFactory.decodeStream(url.openConnection().getInputStream());

        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }

    @Override
    protected void onPostExecute(Bitmap bitmap) {
        super.onPostExecute(bitmap);
        if (pd != null && pd.isShowing()) pd.dismiss();
    }
}

Answer 1

GoogleMap 对象有一个方法来设置地图加载时的回调。在您的 onMapReady 方法中添加以下内容：

mMap.setOnMapLoadedCallback(this);

并在您的 class 中有一个方法，然后实现回调：

@Override
public void OnMapLoaded() {
    AddMarkers addMarkersTask = new AddMarkers(url);
    addMarkersTask.execute();
}

如何先显示地图再下载图像标记？

How to show maps first and then download image markers?

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