启动应用时，我一直收到此错误消息。此代码以谷歌api v1开头，我一直试图完全转换为V2。然而，它只是在我运行时关闭应用程序。它基于在线教程，我正在学习。 有什么建议吗？
package -;
import java.util.List;
import android.content.Intent;
import android.graphics.drawable.Drawable;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.view.Window;
import -.AddItemizedOverlay;
import -.Place;
import -.PlacesList;
import -.R;
import com.google.android.gms.maps.MapFragment;
import com.google.android.gms.maps.SupportMapFragment;
import com.google.android.maps.GeoPoint;
import com.google.android.maps.MapController;
import com.google.android.maps.Overlay;
import com.google.android.maps.OverlayItem;
public class PlacesMapActivity extends FragmentActivity {
// Nearest places
PlacesList nearPlaces;
// Map view
MapFragment mapView;
// Map overlay items
List<Overlay> mapOverlays;
AddItemizedOverlay itemizedOverlay;
GeoPoint geoPoint;
// Map controllers
MapController mc;
double latitude;
double longitude;
OverlayItem overlayitem;
@Override
public void onCreate(Bundle savedInstanceState) {
requestWindowFeature(Window.FEATURE_CUSTOM_TITLE);
super.onCreate(savedInstanceState);
setContentView(R.layout.map_places);
getWindow().setFeatureInt(Window.FEATURE_CUSTOM_TITLE, R.layout.window_title);
Intent i = getIntent();
// Users current geo location
String user_latitude = i.getStringExtra("user_latitude");
String user_longitude = i.getStringExtra("user_longitude");
// Nearplaces list
nearPlaces = (PlacesList) i.getSerializableExtra("near_places");
SupportMapFragment fragment = ( SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map);
// Geopoint to place on map
geoPoint = new GeoPoint((int) (Double.parseDouble(user_latitude) * 1E6),
(int) (Double.parseDouble(user_longitude) * 1E6));
// Drawable marker icon
Drawable drawable_user = this.getResources()
.getDrawable(R.drawable.mark_red);
itemizedOverlay = new AddItemizedOverlay(drawable_user, this);
// Map overlay item
overlayitem = new OverlayItem(geoPoint, "Your Location",
"That is you!");
itemizedOverlay.addOverlay(overlayitem);
mapOverlays.add(itemizedOverlay);
itemizedOverlay.populateNow();
// Drawable marker icon
Drawable drawable = this.getResources()
.getDrawable(R.drawable.mark_blue);
itemizedOverlay = new AddItemizedOverlay(drawable, this);
// These values are used to get map boundary area
// The area where you can see all the markers on screen
int minLat = Integer.MAX_VALUE;
int minLong = Integer.MAX_VALUE;
int maxLat = Integer.MIN_VALUE;
int maxLong = Integer.MIN_VALUE;
// check for null in case it is null
if (nearPlaces.results != null) {
// loop through all the places
for (Place place : nearPlaces.results) {
latitude = place.geometry.location.lat; // latitude
longitude = place.geometry.location.lng; // longitude
// Geopoint to place on map
geoPoint = new GeoPoint((int) (latitude * 1E6),
(int) (longitude * 1E6));
// Map overlay item
overlayitem = new OverlayItem(geoPoint, place.name,
place.vicinity);
itemizedOverlay.addOverlay(overlayitem);
// calculating map boundary area
minLat = (int) Math.min( geoPoint.getLatitudeE6(), minLat );
minLong = (int) Math.min( geoPoint.getLongitudeE6(), minLong);
maxLat = (int) Math.max( geoPoint.getLatitudeE6(), maxLat );
maxLong = (int) Math.max( geoPoint.getLongitudeE6(), maxLong );
}
mapOverlays.add(itemizedOverlay);
// showing all overlay items
itemizedOverlay.populateNow();
}
}
}
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical"
>
<fragment
android:id="@+id/map"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:name="com.google.android.gms.maps.SupportMapFragment" />
</LinearLayout>
05-15 01:04:49.513: W/dalvikvm(12551): threadid=1: thread exiting with uncaught exception (group=0x40aac228)
05-15 01:04:49.513: E/AndroidRuntime(12551): FATAL EXCEPTION: main
05-15 01:04:49.513: E/AndroidRuntime(12551): java.lang.RuntimeException: Unable to start activity ComponentInfo{-/-.PlacesMapActivity}: java.lang.NullPointerException
05-15 01:04:49.513: E/AndroidRuntime(12551): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2194)
05-15 01:04:49.513: E/AndroidRuntime(12551): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2229)
05-15 01:04:49.513: E/AndroidRuntime(12551): at android.app.ActivityThread.access$600(ActivityThread.java:139)
05-15 01:04:49.513: E/AndroidRuntime(12551): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1261)
05-15 01:04:49.513: E/AndroidRuntime(12551): at android.os.Handler.dispatchMessage(Handler.java:99)
05-15 01:04:49.513: E/AndroidRuntime(12551): at android.os.Looper.loop(Looper.java:154)
05-15 01:04:49.513: E/AndroidRuntime(12551): at android.app.ActivityThread.main(ActivityThread.java:4944)
05-15 01:04:49.513: E/AndroidRuntime(12551): at java.lang.reflect.Method.invokeNative(Native Method)
05-15 01:04:49.513: E/AndroidRuntime(12551): at java.lang.reflect.Method.invoke(Method.java:511)
05-15 01:04:49.513: E/AndroidRuntime(12551): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
05-15 01:04:49.513: E/AndroidRuntime(12551): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
05-15 01:04:49.513: E/AndroidRuntime(12551): at dalvik.system.NativeStart.main(Native Method)
05-15 01:04:49.513: E/AndroidRuntime(12551): Caused by: java.lang.NullPointerException
05-15 01:04:49.513: E/AndroidRuntime(12551): at -.PlacesMapActivity.onCreate(PlacesMapActivity.java:74)
05-15 01:04:49.513: E/AndroidRuntime(12551): at android.app.Activity.performCreate(Activity.java:4531)
05-15 01:04:49.513: E/AndroidRuntime(12551): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1071)
05-15 01:04:49.513: E/AndroidRuntime(12551): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2150)
05-15 01:04:49.513: E/AndroidRuntime(12551): ... 11 more
05-15 01:04:51.115: D/Process(12551): killProcess, pid=12551
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="-"
android:versionCode="1"
android:versionName="1.0"
android:largeScreens="true"
android:normalScreens="true"
android:smallScreens="true"
android:resizeable="true"
android:anyDensity="true"
android:theme="@android:style/Theme.NoTitleBar" >
<uses-sdk
android:minSdkVersion="15"
android:targetSdkVersion="17" />
<permission
android:name="-.permission.MAPS_RECEIVE"
android:protectionLevel="signature" />
<uses-feature
android:glEsVersion="0x00020000"
android:required="true" />
<uses-permission android:name="-.permission.MAPS_RECEIVE" />
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="com.google.android.providers.gsf.permission.READ_GSERVICES" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.CALL_PHONE" ></uses-permission>
<application
android:icon="@drawable/applogo12"
android:label="@string/app_name"
android:theme="@style/CustomTheme">
<uses-library android:name="com.google.android.maps" />
<activity
android:name="-.SplashActivity"
android:screenOrientation="portrait">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name=".HomeActivity" android:screenOrientation="portrait"></activity>
<activity android:name=".PlacesMapActivity" android:screenOrientation="portrait"></activity>
<meta-data
android:name="com.google.android.maps.v2.API_KEY"
android:value="-" />
</application>
</manifest>
答案 0 :(得分：1)
在Java堆栈跟踪中，您将寻找对代码的引用，以确定出错的位置。在这种情况下，即：
05-15 01:04:49.513: E/AndroidRuntime(12551): Caused by: java.lang.NullPointerException
05-15 01:04:49.513: E/AndroidRuntime(12551): at -.PlacesMapActivity.onCreate(PlacesMapActivity.java:74)
如果我们假设这一行是第74行：
mapOverlays.add(itemizedOverlay);
然后这个例外是有道理的，因为你永远不会初始化mapOverlays。
除此之外，大部分代码都无法正常工作，因为它试图在Maps V2地图上运行Maps V1。例如，Maps V2没有OverlayItem个实例，也没有ItemizedOverlay , nor GeoPoint`。你可以考虑推出所有这些代码，直到你为它编写Maps V2替换，而不是仅仅崩溃。