如何在 MapView 中绘制显示行车方向的箭头? [英] How can I draw an Arrow showing the driving direction in MapView?

问题描述

我在 Android 应用程序中使用 Google 地图组件 MapView.我可以使用 GPS 位置以点显示我的位置.但我想显示一个箭头，它指出了行驶方向(轴承).我认为我可以使用 bearing 值来获取箭头的角度.

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.

我该怎么做?

推荐答案

假设您已经获得了 Location，然后通过执行以下操作获得方位:

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

float myBearing = location.getBearing();

要实现叠加层，您将使用 ItemizedOverlay 和 叠加项.您需要继承 OverlayItem 以添加旋转 Drawable 的功能.类似的东西:

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 BitmapDrawable 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); 
}

接下来要做的就是将这个新的 Drawable 应用到 OverlayItem 上.这是使用 setMarker() 方法完成的.

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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