java - 使用 GoogleMaps API 的 NULL 指针

Question

我试图找到我的坐标并使用此代码在 map fragment 中显示它，但我的应用程序崩溃了。我正在为其使用最新的 GoogleMap API。

public class gmapp extends FragmentActivity{

// Google Map
private GoogleMap googleMap;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.map);

    setUpIfNeeded();
}

private void setUpIfNeeded() {
    if (googleMap == null)
    {
        googleMap = ((SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map)).getMap();
    if (googleMap != null)
    {
        setUpMap();
    }

  }
}

private void setUpMap() {

    googleMap.setMyLocationEnabled(true);

    LocationManager locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);
    Criteria criteria = new Criteria();
    String provider = locationManager.getBestProvider(criteria , true);
    Location myLocation = locationManager.getLastKnownLocation(provider);
    googleMap.setMapType(GoogleMap.MAP_TYPE_HYBRID);
    double latitude = myLocation.getLatitude();
    double longtitude = myLocation.getLongitude();
    LatLng latLng = new LatLng(latitude , longtitude);
    googleMap.moveCamera(CameraUpdateFactory.newLatLng(latLng));

    googleMap.animateCamera(CameraUpdateFactory.zoomTo(20));
    googleMap.addMarker(new MarkerOptions().position(new LatLng(latitude , longtitude)).title("Im here"));

}

这是我编译后的错误信息。

    09-12 20:10:01.034: E/AndroidRuntime(27507): FATAL EXCEPTION: main
09-12 20:10:01.034: E/AndroidRuntime(27507): Process: com.max.maxo, PID: 27507
09-12 20:10:01.034: E/AndroidRuntime(27507): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.max.maxo/com.max.maxo.gmapp}: java.lang.NullPointerException
09-12 20:10:01.034: E/AndroidRuntime(27507):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2394)
09-12 20:10:01.034: E/AndroidRuntime(27507):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2452)
09-12 20:10:01.034: E/AndroidRuntime(27507):    at android.app.ActivityThread.access$900(ActivityThread.java:172)
09-12 20:10:01.034: E/AndroidRuntime(27507):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1302)
09-12 20:10:01.034: E/AndroidRuntime(27507):    at android.os.Handler.dispatchMessage(Handler.java:102)
09-12 20:10:01.034: E/AndroidRuntime(27507):    at android.os.Looper.loop(Looper.java:136)
09-12 20:10:01.034: E/AndroidRuntime(27507):    at android.app.ActivityThread.main(ActivityThread.java:5586)
09-12 20:10:01.034: E/AndroidRuntime(27507):    at java.lang.reflect.Method.invokeNative(Native Method)
09-12 20:10:01.034: E/AndroidRuntime(27507):    at java.lang.reflect.Method.invoke(Method.java:515)
09-12 20:10:01.034: E/AndroidRuntime(27507):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1268)
09-12 20:10:01.034: E/AndroidRuntime(27507):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1084)
09-12 20:10:01.034: E/AndroidRuntime(27507):    at dalvik.system.NativeStart.main(Native Method)
09-12 20:10:01.034: E/AndroidRuntime(27507): Caused by: java.lang.NullPointerException
09-12 20:10:01.034: E/AndroidRuntime(27507):    at com.max.maxo.gmapp.setUpIfNeeded(gmapp.java:35)
09-12 20:10:01.034: E/AndroidRuntime(27507):    at com.max.maxo.gmapp.onCreate(gmapp.java:29)
09-12 20:10:01.034: E/AndroidRuntime(27507):    at android.app.Activity.performCreate(Activity.java:5451)
09-12 20:10:01.034: E/AndroidRuntime(27507):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1093)
09-12 20:10:01.034: E/AndroidRuntime(27507):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2358)
09-12 20:10:01.034: E/AndroidRuntime(27507):    ... 11 more

在我的 XML 中我只得到了 fragment 图

<fragment
    android:id="@+id/map"
    android:name="com.google.android.gms.maps.MapFragment"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

Answer 1

我找到了!我的问题是我忘了添加

 class="com.google.android.gms.maps.SupportMapFragment"

在我的 map XML 文件中。希望这会对某人有所帮助