NullPointerException: if (cursor.moveToFirst()) { - Java / Android Application for University

[UniversityOfTxtech Students]

My classmates and I have an issue with a project we are building.

We've successfully built an Android app which contains an activity which searches our browser histories / bookmarks for specific urls and launches another activity (successfully) if a match is found as an example of an adult content warning implementation.

This is functioning fine.


Now we are implementing a service class to continually execute every few seconds - in order to execute the search of our recent history using our new service class - but we're experiencing a few issues.


Our problem is when we attempt to add the "Nanny" source code from Nanny.java to the service class so the "Nanny" script will search the history continuously, instead of just once - the "Nanny" application continually force closes - due to a null pointer exception at the initialization of our cursor: `if (cursor.moveToFirst()) {`

Which is a bit strange because the NullPointerException does not occur when the exact same script is executed outside the service class in a test file we have (Main.java)


Our working Main.java and our working service class [which successfully displays a toast every few seconds] as well as our [failed] combination of the two - are shown below:




Empty Service Class:

    public class Service_class extends Service {
    
    
        @Override
        public IBinder onBind(Intent arg0) {
            return null;
        }
    
        @Override
        public int onStartCommand(Intent intent, int flags, int startId) {
            Toast.makeText(this, "Service Started", Toast.LENGTH_LONG).show();
            return START_STICKY;
        }
    
        @Override
        public void onDestroy() {
    
            super.onDestroy();
            Toast.makeText(this, "Service Stopped", Toast.LENGTH_LONG).show();
    
        }
    
        @Override
        public void onCreate() {
            super.onCreate();
        }
    
    }

Working Nanny.java

    import android.app.Activity;
    import android.content.Intent;
    import android.database.Cursor;
    import android.os.Bundle;
    import android.provider.Browser;
    import android.widget.TextView;
    
    public class Nanny extends Activity {
    	
    	String Dirty1 = "www.playboy.com";
    	String Dirty2 = "www.penthouse.com";
    	String Dirty3 = "www.pornhub.com";
    	String Dirty4 = "www.playboy.com";
    	String Dirty5 = "www.playboy.com";
    	String Dirty6 = "www.playboy.com";
    	String Dirty7 = "www.playboy.com";
    	String Dirty8 = "www.playboy.com";
    	String Dirty9 = "www.playboy.com";
    	String Dirty10 = "www.playboy.com";
    
    @Override
    public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.nanny);
    TextView tv = (TextView) findViewById(R.id.hello);
    String[] projection = new String[] { Browser.BookmarkColumns.TITLE,
    Browser.BookmarkColumns.URL };
    Cursor cursor = managedQuery(android.provider.Browser.BOOKMARKS_URI,
            projection, null, null, null);
    String urls = "";
    if (cursor.moveToFirst()) {
    String url1 = null;
    String url2 = null;
    do {
    String url = cursor.getString(cursor.getColumnIndex(Browser.BookmarkColumns.URL));
    
    if (url.toLowerCase().contains(Dirty1)) {
    } else if (url.toLowerCase().contains(Dirty2)) {
    } else if (url.toLowerCase().contains(Dirty3)) {
    } else if (url.toLowerCase().contains(Dirty4)) {
    } else if (url.toLowerCase().contains(Dirty5)) {
    } else if (url.toLowerCase().contains(Dirty6)) {
    } else if (url.toLowerCase().contains(Dirty7)) {
    } else if (url.toLowerCase().contains(Dirty8)) {
    } else if (url.toLowerCase().contains(Dirty9)) {
    } else if (url.toLowerCase().contains(Dirty10)) {
    //if (url.toLowerCase().contains(Filthy)) {
    urls = urls
    + cursor.getString(cursor.getColumnIndex(Browser.BookmarkColumns.TITLE)) + " : "
    + url + "\n";
    Intent intent = new Intent(Nanny.this, Warning.class);
    Nanny.this.startActivity(intent);
    }
    } while (cursor.moveToNext()); 
    tv.setText(urls);
    }}}

Unsuccessful method we've attempted to implement (adding the functioning nanny script to the service class) which causes the NullPointerException: if (cursor.moveToFirst()) {

    
    public class Service_class extends Service {
        String Dirty1 = "www.playboy.com";
        String Dirty2 = "www.penthouse.com";
        String Dirty3 = "www.pornhub.com";
        String Dirty4 = "www.playboy.com";
        String Dirty5 = "www.playboy.com";
        String Dirty6 = "www.playboy.com";
        String Dirty7 = "www.playboy.com";
        String Dirty8 = "www.playboy.com";
        String Dirty9 = "www.playboy.com";
        String Dirty10 = "www.playboy.com";
    
        @Override
        public IBinder onBind(Intent arg0) {
            return null;
        }
    
        @Override
        public int onStartCommand(Intent intent, int flags, int startId) {
            Toast.makeText(this, "Service Started", Toast.LENGTH_LONG).show();
            //setContentView(R.layout.main3);
          //  TextView tv = (TextView) findViewById(R.id.hello);
            String[] projection = new String[] { Browser.BookmarkColumns.TITLE,
            Browser.BookmarkColumns.URL };
            Cursor  cursor = managedQuery(android.provider.Browser.BOOKMARKS_URI,
                    projection, null, null, null);
            String urls = "";
            if (cursor.moveToFirst()) {
            String url1 = null;
            String url2 = null;
            do {
            String url = cursor.getString(cursor.getColumnIndex(Browser.BookmarkColumns.URL));
    
            if (url.toLowerCase().contains(Dirty1)) {
            } else if (url.toLowerCase().contains(Dirty2)) {
            } else if (url.toLowerCase().contains(Dirty3)) {
            } else if (url.toLowerCase().contains(Dirty4)) {
            } else if (url.toLowerCase().contains(Dirty5)) {
            } else if (url.toLowerCase().contains(Dirty6)) {
            } else if (url.toLowerCase().contains(Dirty7)) {
            } else if (url.toLowerCase().contains(Dirty8)) {
            } else if (url.toLowerCase().contains(Dirty9)) {
            } else if (url.toLowerCase().contains(Dirty10)) {
            urls = urls
            + cursor.getString(cursor.getColumnIndex(Browser.BookmarkColumns.TITLE)) + " : "
            + url + "\n";
            Intent warning_intent = new Intent(Service_class.this, Warning.class);
            Service_class.this.startActivity(intent);
            }
            } while (cursor.moveToNext()); 
          //  tv.setText(urls);
    
    
    
    
            return START_STICKY;
    
            }
            return startId;}
        @Override
        public void onDestroy() {
    
            super.onDestroy();
            Toast.makeText(this, "Service Stopped", Toast.LENGTH_LONG).show();
    
        }
    
        @Override
        public void onCreate() {
            super.onCreate();
        }
        private void setContentView(int main3) {
            // TODO Auto-generated method stub
    
        }
    
        private TextView findViewById(int hello) {
            // TODO Auto-generated method stub
            return null;
        }
    
        private Cursor managedQuery(Uri bookmarksUri, String[] projection,
                Object object, Object object2, Object object3) {
            // TODO Auto-generated method stub
            return null;
        }}

LOGCAT (When using combined implementation shown above)


Fails on Line 53: if (cursor.moveToFirst()) {



04-15 18:26:24.761: D/dalvikvm(7466): Late-enabling CheckJNI
04-15 18:26:25.651: D/dalvikvm(7466): GC_FOR_ALLOC freed 82K, 4% free 7379K/7608K, paused 13ms, total 13ms
04-15 18:26:25.651: I/dalvikvm-heap(7466): Grow heap (frag case) to 10.861MB for 3686416-byte allocation
04-15 18:26:25.661: D/dalvikvm(7466): GC_FOR_ALLOC freed 1K, 3% free 10977K/11212K, paused 13ms, total 13ms
04-15 18:26:25.681: D/dalvikvm(7466): GC_CONCURRENT freed <1K, 3% free 10977K/11212K, paused 3ms+2ms, total 17ms
04-15 18:26:25.901: D/dalvikvm(7466): GC_FOR_ALLOC freed <1K, 3% free 10977K/11212K, paused 11ms, total 11ms
04-15 18:26:25.911: I/dalvikvm-heap(7466): Grow heap (frag case) to 17.086MB for 6529744-byte allocation
04-15 18:26:25.931: D/dalvikvm(7466): GC_FOR_ALLOC freed 0K, 2% free 17354K/17592K, paused 13ms, total 13ms
04-15 18:26:25.941: D/dalvikvm(7466): GC_CONCURRENT freed <1K, 2% free 17354K/17592K, paused 3ms+2ms, total 16ms
04-15 18:26:26.051: D/libEGL(7466): loaded /system/lib/egl/libEGL_tegra.so
04-15 18:26:26.061: D/libEGL(7466): loaded /system/lib/egl/libGLESv1_CM_tegra.so
04-15 18:26:26.071: D/libEGL(7466): loaded /system/lib/egl/libGLESv2_tegra.so
04-15 18:26:26.091: D/OpenGLRenderer(7466): Enabling debug mode 0
04-15 18:26:31.181: D/AndroidRuntime(7466): Shutting down VM
04-15 18:26:31.181: W/dalvikvm(7466): threadid=1: thread exiting with uncaught exception (group=0x40f4f930)
04-15 18:26:31.181: E/AndroidRuntime(7466): FATAL EXCEPTION: main
04-15 18:26:31.181: E/AndroidRuntime(7466): java.lang.RuntimeException: Unable to start service com.ut.appdemo.Service_class@41698e90 with Intent { cmp=com.ut.appdemo/.Service_class }: java.lang.NullPointerException
04-15 18:26:31.181: E/AndroidRuntime(7466): at android.app.ActivityThread.handleServiceArgs(ActivityThread.java:2673)
04-15 18:26:31.181: E/AndroidRuntime(7466): at android.app.ActivityThread.access$1900(ActivityThread.java:141)
04-15 18:26:31.181: E/AndroidRuntime(7466): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1331)
04-15 18:26:31.181: E/AndroidRuntime(7466): at android.os.Handler.dispatchMessage(Handler.java:99)
04-15 18:26:31.181: E/AndroidRuntime(7466): at android.os.Looper.loop(Looper.java:137)
04-15 18:26:31.181: E/AndroidRuntime(7466): at android.app.ActivityThread.main(ActivityThread.java:5041)
04-15 18:26:31.181: E/AndroidRuntime(7466): at java.lang.reflect.Method.invokeNative(Native Method)
04-15 18:26:31.181: E/AndroidRuntime(7466): at java.lang.reflect.Method.invoke(Method.java:511)
04-15 18:26:31.181: E/AndroidRuntime(7466): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
04-15 18:26:31.181: E/AndroidRuntime(7466): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
04-15 18:26:31.181: E/AndroidRuntime(7466): at dalvik.system.NativeStart.main(Native Method)
04-15 18:26:31.181: E/AndroidRuntime(7466): Caused by: java.lang.NullPointerException
04-15 18:26:31.181: E/AndroidRuntime(7466): at com.ut.appdemo.Service_class.onStartCommand(Service_class.java:53)
04-15 18:26:31.181: E/AndroidRuntime(7466): at android.app.ActivityThread.handleServiceArgs(ActivityThread.java:2656)
04-15 18:26:31.181: E/AndroidRuntime(7466): ... 10 more

[Steve Luke]

1) Where do you get the cursor fom?

2) What does that method return (always)?