Android - Content Provider query cursor

Question

I cannot seem to grasp the concept of Content provider. I personally think that it bloats the code, it over-complicates it, and is plainly awful.

BTW this will be the first example code of a multi-table ContentProvider that you will find on the web. There is absolutelly NONE other, except for maybe the ContactsProvider ("veeeerrrrry usefull" - by being super-stuffed and indescifrable). I am sure many noobs like me will appreciate this.

Please help me make a simple cursor from a content provider. I have the NORMAL code bellow (using a simple SQLiteOpenHelper), and I need to translate it into content-provider code:

    Button btnp = (Button) findViewById(R.id.btnproc);
    btnp.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
        Context mycontext = getApplicationContext();
        SQLiteDatabase db = new myDbHelper(mycontext).getWritableDatabase();
        String sql = "select _id,data,titlu,cont from notificari where date(data)<=date(datetime())";
        Cursor cursor = db.rawQuery(sql, null);
        Log.w("...MainActivity...", "Record count:"+Integer.toString(curu.getCount()));
            while(curu.moveToNext()){
                String lista = curu.getString(0)+",'"+curu.getString(1)+"',"+curu.getString(2)+",'"+
                        curu.getString(3)+"'";
                Log.e("...MainActivity...", lista);
            }

        }
    });

So I need the cursor to be obtained from content-provider. I have already started developing this "mind-blowing" content-provider, but I have no idea if what I am doing is ok, since it is so overcomplicated. Here it goes (my content-provider needs to refference more than one table):

public class MyFirstProvider extends ContentProvider {
static final String PROVIDER_NAME = "com.mystuff.myapp.MyFirstProvider";
    static final String URL = "content://" + PROVIDER_NAME + "/cte";
    static final String URL2 = "content://" + PROVIDER_NAME + "/clienti";
    static final String URL3 = "content://" + PROVIDER_NAME + "/uzeri";
    static final String URL4 = "content://" + PROVIDER_NAME + "/notificari";
    static final Uri CONTENT_URI = Uri.parse(URL);
    static final Uri CONTENT_URI2 = Uri.parse(URL2);
    static final Uri CONTENT_URI3 = Uri.parse(URL3);
    static final Uri CONTENT_URI4 = Uri.parse(URL4);


    static final int uriCode = 1;
    static final int uriCode1 = 2;
    static final int uriCode2 = 3;
    static final int uriCode3 = 4;
    static final int uriCode4 = 5;
    static final int uriCode5 = 6;
    static final int uriCode6 = 7;
    static final int uriCode7 = 8;


    static final UriMatcher uriMatcher;
    private static HashMap<String, String> values;
    static {
        uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
        uriMatcher.addURI(PROVIDER_NAME, "cte", uriCode);
        uriMatcher.addURI(PROVIDER_NAME, "cte/*", uriCode1);
        uriMatcher.addURI(PROVIDER_NAME, "clienti", uriCode2);
        uriMatcher.addURI(PROVIDER_NAME, "clienti/*", uriCode3);
        uriMatcher.addURI(PROVIDER_NAME, "uzeri", uriCode4);
        uriMatcher.addURI(PROVIDER_NAME, "uzeri/*", uriCode5);
        uriMatcher.addURI(PROVIDER_NAME, "notificari", uriCode6);
        uriMatcher.addURI(PROVIDER_NAME, "notificari/*", uriCode7);
    }

    @Override
    public boolean onCreate() {
        Context context = getContext();
        DatabaseHelper dbHelper = new DatabaseHelper(context);
        db = dbHelper.getWritableDatabase();
        if (db != null) {
            return true;
        }
        return false;
    }

    @Override
    public Cursor query(Uri uri, String[] projection, String selection,String[] selectionArgs, String sortOrder) {
        SQLiteQueryBuilder qb = new SQLiteQueryBuilder();
        switch (uriMatcher.match(uri)) {
            case uriCode:
                qb.setTables(TABLE_NAME);
                qb.setProjectionMap(values);
                break;
            case uriCode2:
                qb.setTables(TABLE_CLIENTI);
                qb.setProjectionMap(values);
                if (sortOrder == null || sortOrder == "") {
                    sortOrder = TCL_NUME_CLIENT;
                }
                break;
            case uriCode6:
                qb.setTables(TABLE_NOTIF);
                qb.setProjectionMap(values);
                break;

            default:
                throw new IllegalArgumentException("Unsupported URI: " + uri);
        }
        Cursor c = qb.query(db, projection, selection, selectionArgs, null,null, sortOrder);
        c.setNotificationUri(getContext().getContentResolver(), uri);
        return c;
    }


    // ... there is other code here regarding the insert,update and delete (not relevant now)

    private SQLiteDatabase db;
    static final String DATABASE_NAME = "mydb";
    static final String TABLE_NAME = "names";
    public static final String TABLE_UZERI = "uzeri";
    public static final String TABLE_NOTIF = "notificari";


    static final int DATABASE_VERSION = 3;
    static final String CREATE_DB_TABLE = " CREATE TABLE " + TABLE_NAME
            + " (_id INTEGER PRIMARY KEY AUTOINCREMENT, "
            + " name TEXT NOT NULL);";

    static final String CREATE_DB_TABLE_NOTIFICARI = "CREATE TABLE IF NOT EXISTS " + TABLE_NOTIF + " (_id INTEGER PRIMARY KEY AUTOINCREMENT, " +
            TNOT_ID_NOT + " INTEGER NOT NULL DEFAULT 0, " +
            TNOT_DATA + " DATE NOT NULL, " +
            TNOT_SURSA + " INTEGER NOT NULL DEFAULT 0, "+
            TNOT_DEST + " INTEGER NOT NULL DEFAULT 0, "+
            TNOT_TIP + " TEXT, "+
            TNOT_TITLU + " TEXT, "+
            TNOT_TITLUCONT + " TEXT, "+
            TNOT_CONT + " TEXT, "+
            TNOT_STERS + " INTEGER DEFAULT 0, "+
            TNOT_NOU + " INTEGER NOT NULL DEFAULT 0)";

   private static class DatabaseHelper extends SQLiteOpenHelper {
        DatabaseHelper(Context context) {
            super(context, DATABASE_NAME, null, DATABASE_VERSION);
        }

        @Override
        public void onCreate(SQLiteDatabase db) {
            db.execSQL(CREATE_DB_TABLE);
            db.execSQL(CREATE_DB_TABLE_UZERI);
            db.execSQL(CREATE_DB_TABLE_NOTIFICARI);
        }

        @Override
        public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
            db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME);
            db.execSQL("DROP TABLE IF EXISTS " + TABLE_UZERI);
            db.execSQL("DROP TABLE IF EXISTS " + TABLE_NOTIFICARI);
            onCreate(db);
        }
    }

I tried to "translate" the Activity code that logs the content of the cursor but it just does NOTHING. It's VERY frustrating. Here is my "translation":

Button btnp = (Button) findViewById(R.id.btnproc);
btnp.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View view) {
        String[] coloane = {MyFirstProvider.TNOT_ID_ID, MyFirstProvider.TNOT_DATA,MyFirstProvider.TNOT_TITLU, MyFirstProvider.TNOT_CONT};
        Cursor curu = MainActivity.this.getContentResolver().query(MyFirstProvider.CONTENT_URI_NOTIF,coloane,null,null,MyFirstProvider.TNOT_DATA);

        Log.w("...MainActivity...", "Recorduri:"+Integer.toString(curu.getCount()));
        while(curu.moveToNext()){
            String lista = curu.getString(0)+",'"+curu.getString(1)+"',"+curu.getString(2)+",'"+
                    curu.getString(3)+"'";
            Log.e("...MainActivity...", lista);
        }

    }
});

I must assure you that the table has 4 records inside (I insert them manually after table creation) Also if I put this code inside the ContentProvider, then the Log displays the content of the table as desired:

Cursor c = qb.query(db, projection, selection, selectionArgs, null,null, sortOrder);
        while(c.moveToNext()){
            Log.w("...Provider...",c.getString(0)+"-"+c.getString(1)+"-"+c.getString(2));
        }

But I do not want to do this in the content provider, I want to do it in the Activity code. What am I doing wrong?

Please help.

Thank you

Answer 1

You don't have to use ContentProvider if you don't have to. Identify your requirements. If the data is private to your application AND if it has to be stored in a table format, then you can access SQLite engine directly in Android without having to go via ContentProvider . But if you want other apps or system to access your app's data, then yes - that's a legitimate use case for ContentProvider .

Nonetheless, i would suggest you read this article - that tells you how to access SQLite engine with and without ContentProvider .

Hope this helps.

Anyways, for your problem at hand, try this -

Cursor c = qb.query(db, projection, selection, selectionArgs, null,null, sortOrder);
if (c == null) {
  // error - log some message
}
else if (c.getCount() < 1) {
  // nothing to show  - log some message
}
else {
  while(c.moveToNext()){
    Log.w("...Provider...",c.getString(0)+"-"+c.getString(1)+"-"+c.getString(2));
  } 
}

Answer 2

Instead of this

btnp.setOnClickListener(new View.OnClickListener

try

btnp.setOnClickListener(this)

and implement onClickListner to the Activity.

In short, instead of casting onClickListener to button, implement it to the whole activity and try.