如何将相机居中以使标记位于屏幕底部？（Google map api V2 Android）

Question

当单击标记时，相机的默认行为是将其居中在屏幕上，但因为我通常在信息窗口中有很长的文本描述，所以实际更改相机位置以使标记位于屏幕底部更方便（使信息窗口位于屏幕中心）。我想我应该可以通过像下面这样覆盖onMarkerClick函数来做到这一点（当此函数返回true时，默认行为被取消）

@Override

public boolean onMarkerClick(final Marker marker) {


    // Google sample code comment : We return false to indicate that we have not

    // consumed the event and that we wish
    // for the default behavior to occur (which is for the camera to move
    // such that the
    // marker is centered and for the marker's info window to open, if it
    // has one).

    marker.showInfoWindow();

            CameraUpdate center=
                CameraUpdateFactory.newLatLng(new LatLng(XXXX,
                                                         XXXX));
            mMap.moveCamera(center);//my question is how to get this center

            // return false;
    return true;
}

编辑：

使用接受答案的步骤解决问题，代码如下：

@Override

    public boolean onMarkerClick(final Marker marker) {

                //get the map container height
        LinearLayout mapContainer = (LinearLayout) findViewById(R.id.map_container);
        container_height = mapContainer.getHeight();

        Projection projection = mMap.getProjection();

        LatLng markerLatLng = new LatLng(marker.getPosition().latitude,
                marker.getPosition().longitude);
        Point markerScreenPosition = projection.toScreenLocation(markerLatLng);
        Point pointHalfScreenAbove = new Point(markerScreenPosition.x,
                markerScreenPosition.y - (container_height / 2));

        LatLng aboveMarkerLatLng = projection
                .fromScreenLocation(pointHalfScreenAbove);

        marker.showInfoWindow();
        CameraUpdate center = CameraUpdateFactory.newLatLng(aboveMarkerLatLng);
        mMap.moveCamera(center);
        return true;



    }

谢谢帮忙^^

Answer 1

如果你不关心地图的放大，只想把标记放在下面，我认为这是一个更简单的解决方案

double center = mMap.getCameraPosition().target.latitude;
double southMap = mMap.getProjection().getVisibleRegion().latLngBounds.southwest.latitude;

double diff = (center - southMap);

double newLat = marker.getPosition().latitude + diff;

CameraUpdate centerCam = CameraUpdateFactory.newLatLng(new LatLng(newLat, marker.getPosition().longitude));

mMap.animateCamera(centerCam);

Answer 2

我更喜欢拉里·麦肯齐（Larry McKenzie）的答案，它不依赖于屏幕投影（即mProjection.toScreenLocation（）），我猜当地图缩放级别较低时，投影分辨率会变差，这让我有时无法获得准确的位置。因此，基于谷歌地图规范的计算肯定会解决这个问题。

下面是将标记从底部移动到屏幕大小的30%的示例代码。

zoom_lvl = mMap.getCameraPosition().zoom;
double dpPerdegree = 256.0*Math.pow(2, zoom_lvl)/170.0;
double screen_height = (double) mapContainer.getHeight();
double screen_height_30p = 30.0*screen_height/100.0;
double degree_30p = screen_height_30p/dpPerdegree;      
LatLng centerlatlng = new LatLng( latlng.latitude + degree_30p, latlng.longitude );         
mMap.animateCamera( CameraUpdateFactory.newLatLngZoom( centerlatlng, 15 ), 1000, null);

Answer 3

我可能会稍后编辑这个答案以提供一些代码，但我认为可以工作的是：

1. 获取所单击标记的LatLng（LatLng M）

请看这里我关于如何获得地图高度的答案。

    // googleMap is a GoogleMap object
    // view is a View object containing the inflated map
    // marker is a Marker object
    Projection projection = googleMap.getProjection();
    LatLng markerPosition = marker.getPosition();
    Point markerPoint = projection.toScreenLocation(markerPosition);
    Point targetPoint = new Point(markerPoint.x, markerPoint.y - view.getHeight() / 2);
    LatLng targetPosition = projection.fromScreenLocation(targetPoint);
    googleMap.animateCamera(CameraUpdateFactory.newLatLng(targetPosition), 1000, null);