我怎么能画一个箭头显示在图形页面行驶方向？ [英] How can I draw an Arrow showing the driving direction in MapView?

问题描述

我用谷歌地图组件图形页面在Android应用程序。我可以使用GPS位置用一个圆点显示我的位置。不过，我想显示一个箭头来代替，这指出了行驶方向（轴承）。我想，我可以使用轴承价值得到箭头的角度。

I use that Google Maps component MapView in an Android application. I can use the GPS location to show my location with a dot. But I would like to show an arrow instead, that points out the driving direction (bearing). I think that I can use the bearing value to get the angle of the arrow.

我怎么能这样做？

推荐答案

假设你已经得到的位置，然后获得轴承做：

Assuming you've got the Location then obtain the bearing by doing:

float myBearing = location.getBearing();

要实现你将要使用的覆盖<一href="http://$c$c.google.com/android/add-ons/google-apis/reference/com/google/android/maps/ItemizedOverlay.html">ItemizedOverlay和<一href="http://$c$c.google.com/android/add-ons/google-apis/reference/com/google/android/maps/OverlayItem.html">OverlayItem.你需要继承OverlayItem添加到旋转绘制对象的功能。是这样的：

To implement the overlay you'll be using ItemizedOverlay and OverlayItem. You'll need to subclass OverlayItem to add the functionality to rotate the Drawable. Something like:

public void rotateDrawable(float angle)
{
  Bitmap arrowBitmap = BitmapFactory.decodeResource(context.getResources(), 
                                                    R.drawable.map_pin);
  // Create blank bitmap of equal size
  Bitmap canvasBitmap = arrowBitmap.copy(Bitmap.Config.ARGB_8888, true);
  canvasBitmap.eraseColor(0x00000000);

  // Create canvas
  Canvas canvas = new Canvas(canvasBitmap);

  // Create rotation matrix
  Matrix rotateMatrix = new Matrix();
  rotateMatrix.setRotate(angle, canvas.getWidth()/2, canvas.getHeight()/2);

  // Draw bitmap onto canvas using matrix
  canvas.drawBitmap(arrowBitmap, rotateMatrix, null);

  return new BitmapDrawable(canvasBitmap); 
}

然后，所有剩下来要做的就是将这种新的可绘制应用到OverlayItem。这是通过使用setMarker（）方法

Then all that remains to be done is to apply this new Drawable to the OverlayItem. This is done using the setMarker() method.

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