Database Programming Code Dissection

Layered Approach Presentation (Activity) DbSampleActivity.java DataAccess (DataSource) CommentsDataSource.java MySQLiteHelper.java Object Class (Entity) Comment.java

Activity (onCreate) public void onCreate() { instantiate and open datasource setupViews addButtonListener updateTable }

Activity (setupViews) dataTable = (TableLayout)findViewById(R.id.data_table); txtcomment = (EditText)findViewById(R.id.txtComment); txtauthor = (EditText)findViewById(R.id.txtAuthor); txtdelauthor = (EditText)findViewById(R.id.txtDelAuthor); btnadd = (Button)findViewById(R.id.btnAdd); btndelete = (Button)findViewById(R.id.btnDelete);

Activity (addButtonListener) btnadd.setOnClickListener(this); btndelete.setOnClickListener(this);

Activity (updateTable) while (dataTable.getChildCount() > 1) { dataTable.removeViewAt(1); } ArrayList > data = datasource.getAllRowsAsArrays(); for (int position=0; position < data.size(); position++) { TableRow tableRow= new TableRow(this); ArrayList row = data.get(position); TextView txtcomment = new TextView(this); txtcomment.setText(row.get(0).toString()); tableRow.addView(txtcomment); TextView txtauthor = new TextView(this); txtauthor.setText(row.get(1).toString()); tableRow.addView(txtauthor); dataTable.addView(tableRow); }

Activity (updateTable) while table has rows { remove first row } place data into an ArrayList ***ArrayList of ArrayList Objects*** loop based on the number of rows of data { instantiate a new TableRow Layout place the data of the current row into an ArrayList Object assign the row values into TextViews add the TextViews into the TableRow add the view to the display screen }

Activity (onClick) public void onClick(View view) { If add then datasource.createComment(fields); updateTable(); If delete then datasource.deleteComment(field); updateTable(); }

DataSource(createComment) public void createComment(String comment, String author) { ContentValues values = new ContentValues(); values.put(MySQLiteHelper.COLUMN_COMMENT, comment); values.put(MySQLiteHelper.COLUMN_AUTHOR, author); try { database.insert(MySQLiteHelper.TABLE_COMMENTS, null, values); } catch(Exception e) { Log.e("DB ERROR", e.toString()); e.printStackTrace(); }

DataSource(createComment) ContentValues used to insert new rows into tables each Content Value object represents a single table row as a map of column names to values

DataSource (getAllRowsAsArrays) public ArrayList > getAllRowsAsArrays() { ArrayList > dataArrays = new ArrayList >(); Cursor cursor; try { cursor = database.query(MySQLiteHelper.TABLE_COMMENTS, new String[]{MySQLiteHelper.COLUMN_COMMENT, MySQLiteHelper.COLUMN_AUTHOR}, null, null, null, null, null); cursor.moveToFirst(); if (!cursor.isAfterLast()) { do { ArrayList dataList = new ArrayList (); dataList.add(cursor.getString(0)); dataList.add(cursor.getString(1)); dataArrays.add(dataList); } while (cursor.moveToNext());} } catch (SQLException e) { Log.e("DB Error", e.toString()); e.printStackTrace(); } return dataArrays; }

DataSource (getAllRowsAsArrays) Cursors Queries in Android are returned as Cursor objects pointers to the result set within the underlying data provide a managed way of controlling your position (row) in the result set of a database query

SQLite Helper Class Database Schema database description declaration of table name and fields

SQLite Helper Class SQL SELECT INSERT UPDATE DELETE