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

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2 回答 2

9

谢谢@CommonsWare,你把我引向了正确的方向。花了相当多的时间玩弄这个。http://code.google.com/android/add-ons/google-apis/reference/com/google/android/maps/MyLocationOverlay.html上的 Javadoc是错误的(或过时的),并且会混淆您的大脑说:

drawMyLocation

此外,如果用户的位置移动到屏幕边缘附近,并且我们在构造函数中获得了 MapController,我们将滚动以使新读数居中。

这是完全错误的。首先,类中没有这样的构造函数。其次,drawMyLocation 仅在当前位置在视界内或屏幕移动时才被调用。因此,如果您收到一个新位置并且此时您没有看到该标记,则它不会被重绘。一般来说,这是一件好事,但如果您想在方法中实现 mc.animateTo 以保持位置居中,则这是一件坏事。

第三,您不需要传递 MapController 来启用 currentLocation,因为您已经拥有 mapView 并从中获取控制器。

所以我最终编写了我自己的类,一旦位置到达 mapView 的边界或不在屏幕上,它就会一直以当前位置为中心:

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;
  }
}
于 2011-03-06T14:46:07.303 回答
5

第 1 步:创建MyLocationOverlay.

步骤#2:覆盖drawMyLocation()并绘制你喜欢的标记。请记住,此方法不仅绘制标记,而且“如果用户的位置移动到屏幕边缘附近,并且我们MapController在构造函数中得到了 a,我们将滚动以重新定位新读数”。

于 2010-11-14T00:13:39.090 回答