android中可见区域外目标注释的方向

Question

我想在屏幕的所有侧面显示方向图像。例如。如果目标的位置是用户位置的右侧并且在可见地图区域之外，那么我想添加一个方向图像，如下图所示（绿色注释是用户位置，红色是目标的方向，超出屏幕范围）：

我在这里找到了 IOS 的解决方案： Direction of target annotation when outside of visible area 但是在android中还没有找到解决方案。

Answer 1

终于找到了解决办法：

//Add at class level
    private static final int NORTH = 1;
    private static final int SOUTH = 2;
    private static final int EAST = 3;
    private static final int WEST = 4;
    private ImageView imgEast;
    private ImageView imgWest;
    private ImageView imgNorth;
    private ImageView imgSouth;

    private LatLng source;
    private LatLng target;

//In onCreate or somewhere else
    imgEast = (ImageView) findViewById(R.id.east);
    imgWest = (ImageView) findViewById(R.id.west);
    imgNorth = (ImageView) findViewById(R.id.north);
    imgSouth = (ImageView) findViewById(R.id.south);

    source = new LatLng(31.499851, 74.317489);
    target = new LatLng(33.736189, 73.096848);

//Add after populating map
            googleMap.setOnCameraChangeListener(new OnCameraChangeListener() {
                @Override
                public void onCameraChange(CameraPosition position) {
                    if(isLocationVisible(source) && !isLocationVisible(target)){

                        double bearing = calculateBearing(source, target);
                        showCardinalPointDirection(bearing);
                    }else{
                        hideCardinalPointers();
                    }
                }
            });

    public boolean isLocationVisible(LatLng latLng){
        LatLngBounds curScreen = googleMap.getProjection()
                .getVisibleRegion().latLngBounds;
        if(curScreen.contains(latLng)){
            return true;
        }else{
            return false;
        }
    }

    private double calculateBearing(LatLng source, LatLng target){
        double lat1 = DegreesToRadians(source.latitude);
        double lon1 = DegreesToRadians(source.longitude);

        double lat2 = DegreesToRadians(target.latitude);
        double lon2 = DegreesToRadians(target.longitude);

        double dLon = lon2 - lon1;

        double y = Math.sin(dLon) * Math.cos(lat2);
        double x = Math.cos(lat1) * Math.sin(lat2) - Math.sin(lat1) * Math.cos(lat2) * Math.cos(dLon);
        double radiansBearing = Math.atan2(y, x);

        if(radiansBearing < 0.0)
            radiansBearing += 2*Math.PI;

        return RadiansToDegrees(radiansBearing);
    }

    private void showCardinalPointDirection(double bearing){
        int direction = cardinalPointWithBearing(bearing);
        View activeDirection = null;
        switch(direction){
        case EAST:
            activeDirection = this.imgEast;
            break;
        case WEST:
            activeDirection = this.imgWest;
            break;
        case SOUTH:
            activeDirection = this.imgSouth;
            break;
        case NORTH:
            activeDirection = this.imgNorth;
            break;
        }

        //Hide all pointers
        hideCardinalPointers();

        //Visible only active direction pointer
        activeDirection.setVisibility(View.VISIBLE);

        //Set rotation to show direction
        activeDirection.setRotation((float)bearing);
    }

    private int cardinalPointWithBearing(double bearing){
        if (bearing > 45.0 && bearing <= 135.0) {
            return EAST;
        } else if (bearing > 135.0 && bearing <= 225.0) {
            return SOUTH;
        } else if (bearing > 225.0 && bearing <= 315.0) {
            return WEST;
        } else {
            return NORTH;
        }
    }

    double DegreesToRadians(double degrees) {
        return degrees * Math.PI / 180.0;
    };

    double RadiansToDegrees(double radians) {
        return radians * 180.0/Math.PI;
    };

    private void hideCardinalPointers(){
        imgEast.setVisibility(View.INVISIBLE);
        imgWest.setVisibility(View.INVISIBLE);
        imgSouth.setVisibility(View.INVISIBLE);
        imgNorth.setVisibility(View.INVISIBLE);
    }