我正在做这里的 MapView 教程:https ://developers.google.com/maps/documentation/android/v1/hello-mapview
问题是它一直在崩溃。这是代码:
package com.example.googlemapstest;
import java.util.List;
import com.google.android.maps.GeoPoint;
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.os.Bundle;
import android.app.Activity;
import android.graphics.drawable.Drawable;
import android.view.Menu;
public class MainActivity extends MapActivity {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_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);
GeoPoint point = new GeoPoint(19240000,-99120000);
OverlayItem overlayitem = new OverlayItem(point, "Hola, Mundo!", "I'm in Mexico City!");
drawable.setBounds(0,0, drawable.getIntrinsicWidth(), drawable.getIntrinsicHeight());
overlayitem.setMarker(drawable);
itemizedoverlay.addOverlay(overlayitem, drawable);
mapOverlays.add(itemizedoverlay);
}
@Override
protected boolean isRouteDisplayed() {
return false;
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
}
和 HelloItemizedOverlay 类:
package com.example.googlemapstest;
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;
public class HelloItemizedOverlay extends ItemizedOverlay
{
private ArrayList<OverlayItem> mOverlays;
Context mContext;
public HelloItemizedOverlay(Drawable defaultMarker) {
super(boundCenterBottom(defaultMarker));
mOverlays = new ArrayList<OverlayItem>();
populate();
}
public void addOverlay(OverlayItem overlay, Drawable drawable) {
overlay.setMarker(drawable);
mOverlays.add(overlay);
populate();
}
@Override
public int size() {
return mOverlays.size();
}
public HelloItemizedOverlay(Drawable defaultMarker, Context context) {
super(boundCenterBottom(defaultMarker));
mContext = context;
mOverlays = new ArrayList<OverlayItem>();
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;
}
@Override
protected OverlayItem createItem(int arg0) {
// TODO Auto-generated method stub
return null;
}
}
我不断得到的例外是
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.googlemapstest/com.example.googlemapstest.MainActivity} : java.lang.NullPointerException
崩溃发生在 itemizedoverlay.addOverlay(overlayitem, drawable) 中的 populate() 行;现在,最初我发现我添加的 OverlayItem 的 mMarker 变量为空,并添加了两行手动设置它。但是,程序仍然不断崩溃!
然后我发现了这个问题:ItemizedOverlay 崩溃的问题,它似乎正在处理相同的错误。
我按照那里的最佳答案中的建议做了,但仍然没有运气。
我相信我已经认真梳理了这一点,并且无法想象 null 错误来自哪里。任何帮助深表感谢。