Android: Binding data to listview from database

Question

I'm trying to pull my data from my SQLite DB and display it in a listview, this is what I have so far but it only puts the first record in the listview. I think the "while (mCursor.moveToNext()){" bit needs changing but not sure how. The original code put each record in a textview on a new line each time.

    if (mCursor == null){
        mCursor.close();
        Log.w("cursor", "null cursor");
    }       

        mCursor.moveToFirst();
    String[] s = null;


    while (mCursor.moveToNext()){

        s = new String[] { foodNameColumn, proteinColumn, fatColumn, carbsColumn };

        mCursor.moveToNext();
    }


    SimpleCursorAdapter adapter = new SimpleCursorAdapter(this, 
            R.layout.aa_four_column,
            mCursor, 
            s, 
            new int[] { R.id.txtCol1, R.id.txtCol2, R.id.txtCol3, R.id.txtCol4 }, 0);

    lvDB.setAdapter(adapter);

Update:

I've changed it so only this code is in the onCreate method, but the same thing happens, one item displayed when there are multiple things in the DB.

            mCursor = dataBase.select("SELECT * FROM " + TABLE_NAME);

        SimpleCursorAdapter adapter = new SimpleCursorAdapter(this, 
                    R.layout.aa_four_column,
                    mCursor, 
                    new String[] { foodNameColumn, proteinColumn, fatColumn, carbsColumn }, 
                    new int[] { R.id.txtCol1, R.id.txtCol2, R.id.txtCol3, R.id.txtCol4 }, 0);

        lvDB.setAdapter(adapter);

aa_column_four.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="horizontal" >

    <TextView
        android:id="@+id/txtCol1"
        android:layout_width="181dp"
        android:layout_height="wrap_content"
        android:text="Column 1 text will end up here!" />

    <TextView
        android:id="@+id/txtCol2"
        android:layout_width="63dp"
        android:layout_height="wrap_content"
        android:text="Column 2 text will end up here!" />

    <TextView
        android:id="@+id/txtCol3"
        android:layout_width="96dp"
        android:layout_height="wrap_content"
        android:text="Column 3 text will end up here!" />

    <TextView
        android:id="@+id/txtCol4"
        android:layout_width="104dp"
        android:layout_height="wrap_content"
        android:text="Column 4 text will end up here!" />

</LinearLayout>

DatabaseManager Class

    public class DataBaseManager extends SQLiteOpenHelper {

    //the MAIN package of your project
    private static String DB_PATH = "/data/data/com.example.activities/databases/";

    //the name of your database
    private static String DB_NAME = "DB_Nutrition";

    private static SQLiteDatabase mDataBase;

    private static DataBaseManager sInstance = null;
    // database version   
    private static final int DATABASE_VERSION = 1;

    /**
     * Constructor Takes and keeps a reference of the passed context in order to
     * access to the application assets and resources.
     */
    DataBaseManager() {
        super(ApplicationContextProvider.getContext(), DB_NAME, null, DATABASE_VERSION);

        try {
            createDataBase();
            openDataBase();
        } catch (IOException e) {
            e.printStackTrace();
        }

    }

    /**
     * Singleton for DataBase
     *
     * @return singleton instance
     */
    public static DataBaseManager instance() {

        if (sInstance == null) {
            sInstance = new DataBaseManager();
        }
        return sInstance;
    }


    /**
     * Creates a empty database on the system and rewrites it with your own
     * database.
     *
     * @throws java.io.IOException io exception
     */
    private void createDataBase() throws IOException {

        boolean dbExist = checkDataBase();

        if (dbExist) {
            // do nothing - database already exist
        } else {

            // By calling this method an empty database will be created into
            // the default system path
            // of your application so we are gonna be able to overwrite that
            // database with our database.
            this.getReadableDatabase();

            try {

                copyDataBase();

            } catch (IOException e) {

                throw new Error("Error copying database");
            }
        }
    }

    /**
     * Check if the database already exist to avoid re-copying the file each
     * time you open the application.
     *
     * @return true if it exists, false if it doesn't
     */
    private boolean checkDataBase() {

        SQLiteDatabase checkDB = null;

        try {
            String myPath = DB_PATH + DB_NAME;
            checkDB = SQLiteDatabase.openDatabase(myPath, null,
                    SQLiteDatabase.OPEN_READONLY);

        } catch (SQLiteException e) {

            // database doesn't exist yet.

        }

        if (checkDB != null) {

            checkDB.close();

        }

        return checkDB != null;
    }

    /**
     * Copies your database from your local assets-folder to the just created
     * empty database in the system folder, from where it can be accessed and
     * handled. This is done by transfering bytestream.
     *
     * @throws java.io.IOException io exception
     */
    public void copyDataBase() throws IOException {

        // Open your local db as the input stream
        InputStream myInput = ApplicationContextProvider.getContext().getAssets().open(DB_NAME);

        // Path to the just created empty db
        String outFileName = DB_PATH + DB_NAME;

        // Open the empty db as the output stream
        OutputStream myOutput = new FileOutputStream(outFileName);

        // transfer bytes from the inputfile to the outputfile
        byte[] buffer = new byte[1024];
        int length;
        while ((length = myInput.read(buffer)) > 0) {
            myOutput.write(buffer, 0, length);
        }

        // Close the streams
        myOutput.flush();
        myOutput.close();
        myInput.close();

    }

    private void openDataBase() throws SQLException {

        // Open the database
        String myPath = DB_PATH + DB_NAME;
        mDataBase = SQLiteDatabase.openDatabase(myPath, null,
                SQLiteDatabase.OPEN_READWRITE);
    }

    /**
     * Select method
     *
     * @param query select query
     * @return - Cursor with the results
     * @throws android.database.SQLException sql exception
     */
    public Cursor select(String query) throws SQLException {
        return mDataBase.rawQuery(query, null);
    }

    /**
     * Insert method
     *
     * @param table  - name of the table
     * @param values values to insert
     * @throws android.database.SQLException sql exception
     */
    public void insert(String table, ContentValues values) throws SQLException {
        mDataBase.insert(table, null, values);
    }

    /**
     * Delete method
     *
     * @param table - table name
     * @param where WHERE clause, if pass null, all the rows will be deleted
     * @throws android.database.SQLException sql exception
     */
    public void delete(String table, String where) throws SQLException {

        mDataBase.delete(table, where, null);

    }

    /**
     * Update method
     *
     * @param table  - table name
     * @param values - values to update
     * @param where  - WHERE clause, if pass null, all rows will be updated
     */
    public void update(String table, ContentValues values, String where) {

        mDataBase.update(table, values, where, null);

    }

    /**
     * Let you make a raw query
     *
     * @param command - the sql comand you want to run
     */
    public void sqlCommand(String command) {
        mDataBase.execSQL(command);
    }

    @Override
    public synchronized void close() {

        if (mDataBase != null)
            mDataBase.close();

        super.close();

    }

    @Override
    public void onCreate(SQLiteDatabase db) {

    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

    }

}

Error

03-03 15:42:13.894: E/SQLiteLog(9809): (14) cannot open file at line 30176 of [00bb9c9ce4]
03-03 15:42:13.894: E/SQLiteLog(9809): (14) os_unix.c:30176: (2) open(/data/data/com.example.activities/databases/DB_Nutrition) - 
03-03 15:42:13.904: E/SQLiteDatabase(9809): Failed to open database '/data/data/com.example.activities/databases/DB_Nutrition'.
03-03 15:42:13.904: E/SQLiteDatabase(9809): android.database.sqlite.SQLiteCantOpenDatabaseException: unknown error (code 14): Could not open database
03-03 15:42:13.904: E/SQLiteDatabase(9809):     at android.database.sqlite.SQLiteConnection.nativeOpen(Native Method)
03-03 15:42:13.904: E/SQLiteDatabase(9809):     at android.database.sqlite.SQLiteConnection.open(SQLiteConnection.java:209)
03-03 15:42:13.904: E/SQLiteDatabase(9809):     at android.database.sqlite.SQLiteConnection.open(SQLiteConnection.java:193)
03-03 15:42:13.904: E/SQLiteDatabase(9809):     at android.database.sqlite.SQLiteConnectionPool.openConnectionLocked(SQLiteConnectionPool.java:463)
03-03 15:42:13.904: E/SQLiteDatabase(9809):     at android.database.sqlite.SQLiteConnectionPool.open(SQLiteConnectionPool.java:185)
03-03 15:42:13.904: E/SQLiteDatabase(9809):     at android.database.sqlite.SQLiteConnectionPool.open(SQLiteConnectionPool.java:177)
03-03 15:42:13.904: E/SQLiteDatabase(9809):     at android.database.sqlite.SQLiteDatabase.openInner(SQLiteDatabase.java:804)
03-03 15:42:13.904: E/SQLiteDatabase(9809):     at android.database.sqlite.SQLiteDatabase.open(SQLiteDatabase.java:789)
03-03 15:42:13.904: E/SQLiteDatabase(9809):     at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:694)
03-03 15:42:13.904: E/SQLiteDatabase(9809):     at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:669)
03-03 15:42:13.904: E/SQLiteDatabase(9809):     at com.example.db_food.DataBaseManager.checkDataBase(DataBaseManager.java:228)
03-03 15:42:13.904: E/SQLiteDatabase(9809):     at com.example.db_food.DataBaseManager.createDataBase(DataBaseManager.java:193)
03-03 15:42:13.904: E/SQLiteDatabase(9809):     at com.example.db_food.DataBaseManager.<init>(DataBaseManager.java:163)
03-03 15:42:13.904: E/SQLiteDatabase(9809):     at com.example.db_food.DataBaseManager.instance(DataBaseManager.java:179)
03-03 15:42:13.904: E/SQLiteDatabase(9809):     at com.example.db_food.MyActivity.onCreate(MyActivity.java:63)
03-03 15:42:13.904: E/SQLiteDatabase(9809):     at android.app.Activity.performCreate(Activity.java:5104)
03-03 15:42:13.904: E/SQLiteDatabase(9809):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
03-03 15:42:13.904: E/SQLiteDatabase(9809):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
03-03 15:42:13.904: E/SQLiteDatabase(9809):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
03-03 15:42:13.904: E/SQLiteDatabase(9809):     at android.app.ActivityThread.access$600(ActivityThread.java:141)
03-03 15:42:13.904: E/SQLiteDatabase(9809):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
03-03 15:42:13.904: E/SQLiteDatabase(9809):     at android.os.Handler.dispatchMessage(Handler.java:99)
03-03 15:42:13.904: E/SQLiteDatabase(9809):     at android.os.Looper.loop(Looper.java:137)
03-03 15:42:13.904: E/SQLiteDatabase(9809):     at android.app.ActivityThread.main(ActivityThread.java:5041)
03-03 15:42:13.904: E/SQLiteDatabase(9809):     at java.lang.reflect.Method.invokeNative(Native Method)
03-03 15:42:13.904: E/SQLiteDatabase(9809):     at java.lang.reflect.Method.invoke(Method.java:511)
03-03 15:42:13.904: E/SQLiteDatabase(9809):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
03-03 15:42:13.904: E/SQLiteDatabase(9809):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
03-03 15:42:13.904: E/SQLiteDatabase(9809):     at dalvik.system.NativeStart.main(Native Method)

Answer 1

It looks like you want to display the data from a table in a ListView, so simply create an Adapter:

SimpleCursorAdapter adapter = new SimpleCursorAdapter(this, 
        R.layout.aa_four_column,
        mCursor, 
        new String[] { foodNameColumn, proteinColumn, fatColumn, carbsColumn }, 
        new int[] { R.id.txtCol1, R.id.txtCol2, R.id.txtCol3, R.id.txtCol4 }, 0);

lvDB.setAdapter(adapter);

(Use this code by itself, you don't need to use any of the other code below but you should read it to understand why most of your code won't do what you are trying to do.)

---

You have a few logical faults.

1) If an object is null you cannot reference any of its method:

if (mCursor == null){
    /* mCursor.close(); This will throw an NullPointerException! */
    Log.w("cursor", "null cursor");
    return;
}       

2) By calling moveToFirst() and moveToNext() before reading a row you skip the first record. Also you are calling moveToNext() twice between reading the records, so you are only reading every other one. Try this instead:

while (mCursor.moveToNext()){
    // Do something
}

3) Now to manually read an actual value from a Cursor you must use a method like getString() or getInt():

List<String> strings = new ArralyList<String>();
while (mCursor.moveToNext()){
    strings.add(mCursor.getString(mCursor.getColumnIndex(foodNameColumn)) + "  " + mCursor.getInt(mCursor.getColumnIndex(proteinColumn)));
}

4) In the original loop, you are not adding any data to s. You are just overwriting s with the same value over and over:

while (mCursor.moveToNext()){
    s = new String[] { foodNameColumn, proteinColumn, fatColumn, carbsColumn };
}

It doesn't matter if this loop executes once or a thousand times, s will always be the same.

Answer 2

It should be like this

s = new String[] { foodNameColumn, proteinColumn, fatColumn, carbsColumn };

SimpleCursorAdapter adapter = new SimpleCursorAdapter(this, 
            R.layout.aa_four_column,
            mCursor, 
            s, 
            new int[] { R.id.txtCol1, R.id.txtCol2, R.id.txtCol3, R.id.txtCol4 }, 0);

Even if your mCursor is null, it is still OK, just that no item is shown in your list.