问题：从 MainActiviy > MapActivity 单击按钮时无法启动活动。
P/s：我按照这个地图教程更改了类名并将所有元素复制到我的项目工作区。本教程
按钮监听器
public void onClick(View v) {
Intent intent = new Intent(getApplicationContext(),
MapActivity.class);
startActivity(intent);}
日志猫：
07-31 02:22:58.267: E/AndroidRuntime(20784): FATAL EXCEPTION: main
07-31 02:22:58.267: E/AndroidRuntime(20784): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.fa.financeassistant/com.fa.financeassistant.MapActivity}: java.lang.NullPointerException
07-31 02:22:58.267: E/AndroidRuntime(20784): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2308)
07-31 02:22:58.267: E/AndroidRuntime(20784): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2358)
07-31 02:22:58.267: E/AndroidRuntime(20784): at android.app.ActivityThread.access$600(ActivityThread.java:153)
07-31 02:22:58.267: E/AndroidRuntime(20784): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1247)
07-31 02:22:58.267: E/AndroidRuntime(20784): at android.os.Handler.dispatchMessage(Handler.java:99)
07-31 02:22:58.267: E/AndroidRuntime(20784): at android.os.Looper.loop(Looper.java:137)
07-31 02:22:58.267: E/AndroidRuntime(20784): at android.app.ActivityThread.main(ActivityThread.java:5227)
07-31 02:22:58.267: E/AndroidRuntime(20784): at java.lang.reflect.Method.invokeNative(Native Method)
07-31 02:22:58.267: E/AndroidRuntime(20784): at java.lang.reflect.Method.invoke(Method.java:511)
07-31 02:22:58.267: E/AndroidRuntime(20784): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:795)
07-31 02:22:58.267: E/AndroidRuntime(20784): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:562)
07-31 02:22:58.267: E/AndroidRuntime(20784): at dalvik.system.NativeStart.main(Native Method)
07-31 02:22:58.267: E/AndroidRuntime(20784): Caused by: java.lang.NullPointerException
07-31 02:22:58.267: E/AndroidRuntime(20784): at com.fa.financeassistant.MapActivity.onCreate(MapActivity.java:46)
07-31 02:22:58.267: E/AndroidRuntime(20784): at android.app.Activity.performCreate(Activity.java:5104)
07-31 02:22:58.267: E/AndroidRuntime(20784): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
07-31 02:22:58.267: E/AndroidRuntime(20784): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2262)
07-31 02:22:58.267: E/AndroidRuntime(20784): ... 11 more
我的 MapActivity 类
package com.fa.financeassistant;
import java.util.ArrayList;
import android.R.array;
import android.app.ActionBar;
import android.app.Activity;
import android.app.ProgressDialog;
import android.content.Context;
import android.location.Criteria;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.widget.ArrayAdapter;
import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.MapFragment;
import com.google.android.gms.maps.model.BitmapDescriptorFactory;
import com.google.android.gms.maps.model.CameraPosition;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.MarkerOptions;
public class MapActivity extends Activity {
private final String TAG = getClass().getSimpleName();
private GoogleMap mMap;
private String[] places;
private LocationManager locationManager;
private Location loc;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.mapactivity);
initCompo();
places = getResources().getStringArray(R.array.places);
currentLocation();
final ActionBar actionBar = getActionBar();
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_LIST);
actionBar.setListNavigationCallbacks(ArrayAdapter.createFromResource(
this, R.array.places, android.R.layout.simple_list_item_1),
new ActionBar.OnNavigationListener() {
@Override
public boolean onNavigationItemSelected(int itemPosition,
long itemId) {
Log.e(TAG,
places[itemPosition].toLowerCase().replace("-",
"_"));
if (loc != null) {
mMap.clear();
new GetPlaces(MapActivity.this,
places[itemPosition].toLowerCase().replace(
"-", "_").replace(" ", "_")).execute();
}
return true;
}
});
}
private class GetPlaces extends AsyncTask<Void, Void, ArrayList<Place>> {
private ProgressDialog dialog;
private Context context;
private String places;
public GetPlaces(Context context, String places) {
this.context = context;
this.places = places;
}
@Override
protected void onPostExecute(ArrayList<Place> result) {
super.onPostExecute(result);
if (dialog.isShowing()) {
dialog.dismiss();
}
for (int i = 0; i < result.size(); i++) {
mMap.addMarker(new MarkerOptions()
.title(result.get(i).getName())
.position(
new LatLng(result.get(i).getLatitude(), result
.get(i).getLongitude()))
.icon(BitmapDescriptorFactory
.fromResource(R.drawable.pin))
.snippet(result.get(i).getVicinity()));
}
CameraPosition cameraPosition = new CameraPosition.Builder()
.target(new LatLng(result.get(0).getLatitude(), result
.get(0).getLongitude())) // Sets the center of the map to
// Mountain View
.zoom(14) // Sets the zoom
.tilt(30) // Sets the tilt of the camera to 30 degrees
.build(); // Creates a CameraPosition from the builder
mMap.animateCamera(CameraUpdateFactory
.newCameraPosition(cameraPosition));
}
@Override
protected void onPreExecute() {
super.onPreExecute();
dialog = new ProgressDialog(context);
dialog.setCancelable(false);
dialog.setMessage("Loading");
dialog.isIndeterminate();
dialog.show();
}
@Override
protected ArrayList<Place> doInBackground(Void... arg0) {
PlacesService service = new PlacesService(
"AIzaSyBquLw9vJPDHAZO8kzKw6ft0bPxsgBmblg");
ArrayList<Place> findPlaces = service.findPlaces(loc.getLatitude(), // 28.632808
loc.getLongitude(), places); // 77.218276
for (int i = 0; i < findPlaces.size(); i++) {
Place placeDetail = findPlaces.get(i);
Log.e(TAG, "places : " + placeDetail.getName());
}
return findPlaces;
}
}
private void initCompo() {
mMap = ((MapFragment) getFragmentManager().findFragmentById(R.id.map))
.getMap();
}
private void currentLocation() {
locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
String provider = locationManager
.getBestProvider(new Criteria(), false);
Location location = locationManager.getLastKnownLocation(provider);
if (location == null) {
locationManager.requestLocationUpdates(provider, 0, 0, listener);
} else {
loc = location;
new GetPlaces(MapActivity.this, places[0].toLowerCase().replace(
"-", "_")).execute();
Log.e(TAG, "location : " + location);
}
}
private LocationListener listener = new LocationListener() {
@Override
public void onStatusChanged(String provider, int status, Bundle extras) {
}
@Override
public void onProviderEnabled(String provider) {
}
@Override
public void onProviderDisabled(String provider) {
}
@Override
public void onLocationChanged(Location location) {
Log.e(TAG, "location update : " + location);
loc = location;
locationManager.removeUpdates(listener);
}
};
}
解决方案：除了下面给出的答案。我通过删除这条线来应用快速修复并像魅力一样工作！感谢所有帮助过我的人。祝你今天过得愉快 ：）
android:theme="@style/Theme.NoTitle"