如何在显示地图之前获取要加载的标记和 newLatLngZoom 位置？

Question

我有一个 Activity，它在加载时会加载并显示地图片段。问题是当 activity 打开时，会显示一张空地图。然后几秒钟后，地图更新为 myGoogleMap.moveCamera(CameraUpdateFactory.newLatLngZoom(marker, 4));

给出的正确位置

如何才能使地图仅在 moveCamera 行设置正确位置后显示？

这是我的 Activity:

的代码

public class actWhereBeen extends AppCompatActivity implements OnMapReadyCallback {

    private GoogleMap myGoogleMap;
    private static String TAG = "actWhereBeen";
    Context context;
    clsSqliteHandler mySqliteHandler = new clsSqliteHandler();
    ProgressBar progressBar;
    SQLiteDatabase sqLiteDatabase;
    SupportMapFragment mMapFragment = SupportMapFragment.newInstance();




    @Override
    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_act_where_been);
        context = this;
        sqLiteDatabase = openOrCreateDatabase("wildlife_db",MODE_PRIVATE,null);

        addMapFragment();


//        progressBar = findViewById(R.id.progressBar);
////
//        progressBar.setVisibility(View.VISIBLE);
////
//        locationManager = (LocationManager) context.getSystemService(Context.LOCATION_SERVICE);
//        fusedLocationProviderClient = LocationServices.getFusedLocationProviderClient(context);
//
//        dblCrntLat = -27.8885;
//        dblCrntLong = 32.7777;
//
//        SupportMapFragment supportMapFragment = (SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.mapWhere);
//        supportMapFragment.getMapAsync(this);



    }





    private void addMapFragment() {
        mMapFragment.getMapAsync(this);
        getSupportFragmentManager().beginTransaction()
                .replace(R.id.mapWhere, mMapFragment)
                .commit();

    }



    @Override
    public void onMapReady(GoogleMap googleMap) {

        myGoogleMap = googleMap;

        Region region = new Region();
        region = region.getRegionFromKey(sqLiteDatabase,1);

        Double dblLatCenter = region.getCenter_lat();
        Double dblLongCenter = region.getCenter_long();

        LatLng marker = new LatLng(dblLatCenter, dblLongCenter);
        myGoogleMap.getUiSettings().setRotateGesturesEnabled(false);
        myGoogleMap.moveCamera(CameraUpdateFactory.newLatLngZoom(marker, 4));

        Cursor csrSightings = getSightingsCursor();
        addMarkersToMap(csrSightings);

    }





    public Cursor getSightingsCursor() {

        // an array for the filter values
        List<String> arrWhere = new ArrayList<String>();
        String[] finalValue = new String[ arrWhere.size() ];
        arrWhere.toArray( finalValue );

        // an array for the columns to return
        List<String> arrCols = new ArrayList<String>();
        arrCols.add("latitude");
        arrCols.add("longitude");

        Cursor csrCoords = mySqliteHandler.getCursorAllPurpose(false, "tbl_fact_sightings", arrCols, "", arrWhere,
                null, null, null);

        return csrCoords;

    }


    public void addMarkersToMap(Cursor csrSightings){

        int intCount = csrSightings.getCount();

        if (intCount > 0) {

            for( csrSightings.moveToFirst(); !csrSightings.isAfterLast(); csrSightings.moveToNext() ) {

                Double dblLat = Double.valueOf(csrSightings.getString(0));
                Double dblLong = Double.valueOf(csrSightings.getString(1));
                populateMap(dblLat, dblLong);

            }

        }


    }





    public void populateMap(Double dblLat, Double dblLong){

        // Create a mutable bitmap
        Bitmap bitMap = Bitmap.createBitmap(100, 100, Bitmap.Config.ARGB_8888);
        bitMap = bitMap.copy(bitMap.getConfig(), true);

        // Construct a canvas with the specified bitmap to draw into
        Canvas canvas = new Canvas(bitMap);

        // Create a new paint with default settings.
        Paint paint = new Paint();

        // smooths out the edges of what is being drawn
        paint.setAntiAlias(true);

        // set color
        paint.setColor(Color.BLUE);

        // set style
        paint.setStyle(Paint.Style.FILL);

        // set stroke
        paint.setStrokeWidth(4.5f);

        // draw circle with radius 30
        canvas.drawCircle(50, 50, 15, paint);

        LatLng marker = new LatLng(dblLat, dblLong);
        myGoogleMap.moveCamera(CameraUpdateFactory.newLatLngZoom(marker, 3));
        myGoogleMap.addMarker(new MarkerOptions().title("Test")
                .position(marker)
                .icon(BitmapDescriptorFactory.fromBitmap(bitMap)
                ));
    }
}

Answer 1

只创建一次标记图标位图。

public class actWhereBeen extends AppCompatActivity implements OnMapReadyCallback {
Bitmap mMarkerIcon; // "global" variable
...

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    mMarkerIcon = Bitmap.createBitmap(100, 100, Bitmap.Config.ARGB_8888);
    mMarkerIcon = mMarkerIcon.copy(mMarkerIcon.getConfig(), true);

    // Construct a canvas with the specified bitmap to draw into
    Canvas canvas = new Canvas(mMarkerIcon);

    // Create a new paint with default settings.
    Paint paint = new Paint();

    // smooths out the edges of what is being drawn
    paint.setAntiAlias(true);

    // set color
    paint.setColor(Color.BLUE);

    // set style
    paint.setStyle(Paint.Style.FILL);

    // set stroke
    paint.setStrokeWidth(4.5f);

    // draw circle with radius 30
    canvas.drawCircle(50, 50, 15, paint);
    ...
}
}

在populateMap()中刚刚设置了之前创建的位图：

LatLng marker = new LatLng(dblLat, dblLong);
myGoogleMap.moveCamera(CameraUpdateFactory.newLatLngZoom(marker, 3));
myGoogleMap.addMarker(new MarkerOptions().title("Test")
        .position(marker)
        .icon(BitmapDescriptorFactory.fromBitmap(mMarkerIcon)
    ));

删除 moveCamera() 调用，行：

myGoogleMap.moveCamera(CameraUpdateFactory.newLatLngZoom(marker, 3));

来自public void populateMap(Double dblLat, Double dblLong)方法：

public void populateMap(Double dblLat, Double dblLong){
    LatLng marker = new LatLng(dblLat, dblLong);
    myGoogleMap.moveCamera(CameraUpdateFactory.newLatLngZoom(marker, 3));  // <- this line should be removed
    myGoogleMap.addMarker(new MarkerOptions().title("Test")
            .position(marker)
            .icon(BitmapDescriptorFactory.fromBitmap(bitMap)
            ));

}

这不是优化的全部，而是改进代码的方向。

如何在显示地图之前获取要加载的标记和 newLatLngZoom 位置？

How to get Markers and newLatLngZoom position to load before Map is displayed?

android

google-maps

supportmapfragment