I'm pretty new to Android development so I'm sure this is going to turn out to be something stupid that I've missed, but I have two activities: StartScreen and Map. StartScreen is just simple text and a button, which is supposed to then take you to the Map activity.
I've already tried reducing the Map activity down to almost nothing, and I'm sure it's nothing in there that's causing the error, but I just can't figure out what is.
This is the logcat output for the error, it happens when I press the button linking the two activities:
04-28 20:40:24.097: E/AndroidRuntime(13458): FATAL EXCEPTION: main
04-28 20:40:24.097: E/AndroidRuntime(13458): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.rr.freespace/com.rr.freespace.Map}: java.lang.NullPointerException
04-28 20:40:24.097: E/AndroidRuntime(13458): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2110)
04-28 20:40:24.097: E/AndroidRuntime(13458): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2229)
04-28 20:40:24.097: E/AndroidRuntime(13458): at android.app.ActivityThread.access$600(ActivityThread.java:139)
04-28 20:40:24.097: E/AndroidRuntime(13458): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1261)
04-28 20:40:24.097: E/AndroidRuntime(13458): at android.os.Handler.dispatchMessage(Handler.java:99)
04-28 20:40:24.097: E/AndroidRuntime(13458): at android.os.Looper.loop(Looper.java:154)
04-28 20:40:24.097: E/AndroidRuntime(13458): at android.app.ActivityThread.main(ActivityThread.java:4945)
04-28 20:40:24.097: E/AndroidRuntime(13458): at java.lang.reflect.Method.invokeNative(Native Method)
04-28 20:40:24.097: E/AndroidRuntime(13458): at java.lang.reflect.Method.invoke(Method.java:511)
04-28 20:40:24.097: E/AndroidRuntime(13458): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
04-28 20:40:24.097: E/AndroidRuntime(13458): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
04-28 20:40:24.097: E/AndroidRuntime(13458): at dalvik.system.NativeStart.main(Native Method)
04-28 20:40:24.097: E/AndroidRuntime(13458): Caused by: java.lang.NullPointerException
04-28 20:40:24.097: E/AndroidRuntime(13458): at android.content.ContextWrapper.getPackageName(ContextWrapper.java:127)
04-28 20:40:24.097: E/AndroidRuntime(13458): at android.content.ComponentName.<init>(ComponentName.java:75)
04-28 20:40:24.097: E/AndroidRuntime(13458): at android.content.Intent.<init>(Intent.java:3475)
04-28 20:40:24.097: E/AndroidRuntime(13458): at com.rr.freespace.Map.<init>(Map.java:12)
04-28 20:40:24.097: E/AndroidRuntime(13458): at java.lang.Class.newInstanceImpl(Native Method)
04-28 20:40:24.097: E/AndroidRuntime(13458): at java.lang.Class.newInstance(Class.java:1319)
04-28 20:40:24.097: E/AndroidRuntime(13458): at android.app.Instrumentation.newActivity(Instrumentation.java:1039)
04-28 20:40:24.097: E/AndroidRuntime(13458): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2101)
Here's my StartScreen.java:
package com.rr.freespace;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
public class StartScreen extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_start_screen);
}
public void doIt(View view) { // Do something in response to button }
Intent intent = new Intent(this, Map.class);
startActivity(intent);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.start_screen, menu);
return true;
}
}
The activity_start_screen.xml layout file:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".StartScreen" >
<TextView
android:id="@+id/textView2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:layout_marginTop="180dp"
android:text="@string/hometext2"
android:textAppearance="?android:attr/textAppearanceLarge" />
<Button
android:id="@+id/button1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_centerInParent="true"
android:layout_centerVertical="true"
android:layout_margin="20dp"
android:text="@string/doit"
android:onClick="doIt" />
</RelativeLayout>
And finally, the manifest file:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.rr.freespace"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="11"
android:targetSdkVersion="17" />
<permission
android:name="com.example.mapdemo.permission.MAPS_RECEIVE"
android:protectionLevel="signature"/>
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/>
<uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="com.rr.freespace.permission.MAPS_RECEIVE"/>
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<uses-permission android:name="com.google.android.providers.gsf.permission.READ_GSERVICES"/>
<uses-feature
android:glEsVersion="0x00020000"
android:required="true"/>
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme">
<uses-library android:name="com.google.android.maps" />
<meta-data
android:name="com.google.android.maps.v2.API_KEY"
android:value="AIzaSyBaoeVjdRY312vJ5KMLXxmzpKHhPiYqASo"/>
<activity
android:name="com.rr.freespace.StartScreen"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name="com.rr.freespace.Map"
android:label="@string/app_name" >
</activity>
</application>
</manifest>
I hope someone can figure out what's going on here, because I can't! Cheers!
EDIT: here's the map.java code, there may be more errors in here that I haven't got to yet, because I hacked most of this together yesterday before I had access to an android device:
package com.rr.freespace;
import android.app.Activity;
import android.app.AlertDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;
import android.provider.Settings;
import android.view.Menu;
import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.GoogleMapOptions;
import com.google.android.gms.maps.MapFragment;
import com.google.android.gms.maps.model.LatLng;
public class Map extends Activity {
final Context context = this;
Intent goback = new Intent(this, StartScreen.class);
protected LocationManager locationManager;
protected LocationListener listener;
private GoogleMap mMap;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_map);
LocationManager locationManager = (LocationManager) this.getSystemService(Context.LOCATION_SERVICE);
final boolean gpsEnabled = locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER);
if (!gpsEnabled) {
AlertDialog.Builder gpssettings = new AlertDialog.Builder(context);
gpssettings.setMessage(R.string.gpstext)
.setTitle(R.string.gpstitle);
gpssettings.setPositiveButton(R.string.gpsok, new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
// User clicked OK button
enableLocationSettings();
}
});
gpssettings.setNegativeButton(R.string.gpscancel, new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
// User cancelled the dialog
startActivity(goback);
}
});
}
mMap = ((MapFragment) getFragmentManager().findFragmentById(R.id.map)).getMap();
GoogleMapOptions options = new GoogleMapOptions();
options.mapType(GoogleMap.MAP_TYPE_NORMAL)
.compassEnabled(false)
.rotateGesturesEnabled(false)
.tiltGesturesEnabled(false);
//Get GPS data
final LocationListener listener = new LocationListener() {
@Override
public void onLocationChanged(Location location) {
// A new location update is received. Do something useful with it. Update the UI with
// the location update.
final LatLng position = new LatLng(location.getLatitude(),location.getLongitude());
mMap.animateCamera(CameraUpdateFactory.newLatLngZoom(position, 15));
}
@Override
public void onProviderDisabled(String provider) {
}
@Override
public void onProviderEnabled(String provider) {
}
@Override
public void onStatusChanged(String provider, int status, Bundle extras) {
}
};
locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER,
1000, // 10-second interval.
5, // 5 meters.
listener);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.map, menu);
return true;
}
private void enableLocationSettings() {
Intent settingsIntent = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);
startActivity(settingsIntent);
}
protected void onStop() {
super.onStop();
locationManager.removeUpdates(listener);
}
}
