java - myLocationOverlay 更改标记

Question

如何更改谷歌地图中 MyLocationOverlay 的默认蓝色动画标记？

Answer 1

谢谢@CommonsWare，你引导我朝着正确的方向前进。花了相当多的时间来摆弄这个。 http://code.google.com/android/add-ons/google-apis/reference/com/google/android/maps/MyLocationOverlay.html 上的 Javadoc只是错误的(或过时的)并且会扰乱你的大脑，它说:

drawMyLocation

Also, if the user's position moves near the edge of the screen, and we've been given a MapController in our constructor, we'll scroll to recenter the new reading.

这是完全错误的。首先，类中没有这样的构造函数。其次，drawMyLocation 仅在当前 Location 在视界内或屏幕移动时才会被调用。因此，如果您收到一个新位置并且此时没有看到标记，则不会重新绘制它。这在一般情况下是一件好事，但如果您想在方法中实现 mc.animateTo 以保持位置居中，这将是一件坏事。

第三，您不需要传递 MapController 来启用 currentLocation，因为您已经拥有 mapView 并从中获取 Controller ..

所以我最终编写了自己的类，一旦位置到达 mapView 的边界或离开屏幕，它就会以当前位置为中心:

public class CurrentLocationOverlay extends MyLocationOverlay {

  // TODO: use dynamic calculation?
  private final static int PADDING_ACTIVE_ZOOM     = 50;

  private MapController    mc;
  private Bitmap           marker;
  private Point            currentPoint            = new Point();

  private boolean          centerOnCurrentLocation = true;

  private int              height;
  private int              width;

  /**
   * By default this CurrentLocationOverlay will center on the current location, if the currentLocation is near the
   * edge, or off the screen. To dynamically enable/disable this, use {@link #setCenterOnCurrentLocation(boolean)}.
   *
   * @param context
   * @param mapView
   */
  public CurrentLocationOverlay(Context context, MapView mapView) {
    super(context, mapView);
    this.mc = mapView.getController();
    this.marker = BitmapFactory.decodeResource(context.getResources(), R.drawable.position);
  }

  @Override
  protected void drawMyLocation(Canvas canvas, MapView mapView, Location lastFix, GeoPoint myLocation, long when) {
    // TODO: find a better way to get height/width once the mapView is layed out correctly
    if (this.height == 0) {
      this.height = mapView.getHeight();
      this.width = mapView.getWidth();
    }
    mapView.getProjection().toPixels(myLocation, currentPoint);
    canvas.drawBitmap(marker, currentPoint.x, currentPoint.y - 40, null);
  }

  @Override
  public synchronized void onLocationChanged(Location location) {
    super.onLocationChanged(location);
    // only move to new position if enabled and we are in an border-area
    if (mc != null && centerOnCurrentLocation && inZoomActiveArea(currentPoint)) {
      mc.animateTo(getMyLocation());
    }
  }

  private boolean inZoomActiveArea(Point currentPoint) {
    if ((currentPoint.x > PADDING_ACTIVE_ZOOM && currentPoint.x < width - PADDING_ACTIVE_ZOOM)
        && (currentPoint.y > PADDING_ACTIVE_ZOOM && currentPoint.y < height - PADDING_ACTIVE_ZOOM)) {
      return false;
    }
    return true;
  }

  public void setCenterOnCurrentLocation(boolean centerOnCurrentLocation) {
    this.centerOnCurrentLocation = centerOnCurrentLocation;
  }
}