逐项叠加教程

Question

我正在尝试将地图合并到我正在开发的应用程序中，因此我正在学习如何将它们与 ItemizedOverlay 功能一起使用。我浏览了dev-android上的教程，除了这一行之外一切都很好。

public class HelloMapViewActivity extends MapActivity {
    @Override
    protected boolean isRouteDisplayed() 
    {
        return true;
    }

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) 
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        MapView mapView = (MapView) findViewById(R.id.mapview);
        mapView.setBuiltInZoomControls(true);

        List<Overlay> mapOverlays = mapView.getOverlays();
        Drawable drawable = this.getResources().getDrawable(R.drawable.androidmarker);
        HelloItemizedOverlay itemizedoverlay = new HelloItemizedOverlay(drawable); //this is the error

        GeoPoint point = new GeoPoint(19240000,-99120000);
        OverlayItem overlayitem = new OverlayItem(point, "Hola, Mundo!", "I'm in Mexico City!");

        itemizedoverlay.addOverlay(overlayitem);
        mapOverlays.add(itemizedoverlay);
    }

}

问题说：

The constructor HelloItemizedOverlay(drawable) is undefined, 

谁能告诉我我做错了什么？同样，当我按照 Eclipse 告诉我的操作并在参数中将 null 放在它旁边时，它会清除问题，但不会在地图上显示可绘制对象。

Answer 1

我认为这是一个很好的基础学习资源http://developer.android.com/resources/tutorials/views/hello-mapview.html

Answer 2

这是我使用 Google 地图时 HelloItemizedOverlay 的示例：

import java.util.ArrayList;

import android.app.AlertDialog;
import android.content.Context;
import android.graphics.drawable.Drawable;

import com.google.android.maps.ItemizedOverlay;
import com.google.android.maps.OverlayItem;

@SuppressWarnings("rawtypes")
public class HelloItemizedOverlay extends ItemizedOverlay {
    private ArrayList<OverlayItem> mOverlays = new ArrayList<OverlayItem>();
    Context mContext;

    public HelloItemizedOverlay(Drawable defaultMarker) {
        super(boundCenterBottom(defaultMarker));
    }

    public HelloItemizedOverlay(Drawable defaultMarker, Context context) {
        super(boundCenterBottom(defaultMarker));
        mContext = context;
    }

    @Override
    protected OverlayItem createItem(int i) {
        return mOverlays.get(i);
    }

    @Override
    public int size() {
        return mOverlays.size();
    }

    public void addOverlay(OverlayItem overlay) {
        mOverlays.add(overlay);
        populate();
    }

    @Override
    protected boolean onTap(int index) {
        OverlayItem item = mOverlays.get(index);
        AlertDialog.Builder dialog = new AlertDialog.Builder(mContext);
        dialog.setTitle(item.getTitle());
        dialog.setMessage(item.getSnippet());
        dialog.show();
        return true;
    }
}

Answer 3

HelloitemizedOverlay konstructor 也需要上下文。