Question

我试图修改HelloGoogleMaps教程，因此我可以使用for循环填充列表，而不是单独输入。采取婴儿步骤，我尝试只添加一个点，但当我调用GeoPoint列表的添加方法时，我得到一个空指针异常。感谢。

    import java.util.List;
    import com.google.android.maps.GeoPoint;
    //import com.google.android.maps.ItemizedOverlay;
    import com.google.android.maps.MapActivity;
    import com.google.android.maps.MapView;
    import com.google.android.maps.Overlay;
    import com.google.android.maps.OverlayItem;

    import android.graphics.drawable.Drawable;

    import android.os.Bundle;        
public class HelloGoogleMaps extends MapActivity {
/** Called when the activity is first created. */

public List<GeoPoint> geoPoints;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);


    //allows zooming
    MapView mapView = (MapView) findViewById(R.id.mapview);
    mapView.setBuiltInZoomControls(true);



   List<Overlay> mapOverlays = mapView.getOverlays();
    Drawable drawable = this.getResources().getDrawable(R.drawable.icon);
    HelloItemizedOverlay itemizedoverlay = new HelloItemizedOverlay(drawable);

    //create adding points
   GeoPoint point1 = new GeoPoint(19240000,-99120000);
  geoPoints.add(point1);//<<<<<<-------this is where i get the exception

//eventual for loop goes here
}



@Override
protected boolean isRouteDisplayed() {
    return false;
}
 }//end Map Activity

Answer 1

您需要初始化列表：

private List<GeoPoint> geoPoints = new ArrayList<GeoPoint>();
// And also make it private...

使用GeoPoint <list> .add（point）</list>时出现空指针异常

1 个答案: