Slide 14.9: TestDatabase.java (cont.)

TestDatabase.java (Cont.)

int id = view.getId( ); if ( id == R.id.add ) { if ( id == R.id.delete ) {

The IDs add and delete are defined in the file main.xml.

String[ ] comments = new String[ ] { "Cool", "Very nice", "Hate it" };

Create a string array comments with three elements “Cool,” “Very nice,” and “Hate it.”

int nextInt = new Random( ).nextInt( 3 );

The method nextInt(int n) returns a pseudo-random uniformly distributed integer in the half-open range [0, n).

comment = datasource.createComment( comments[nextInt] );

The class CommentsDataSource is this application’s DAO (data access object), which provides an abstract interface to a database. The method createComment, which adds a new comment to the database and returns the comment, is implemented as follows:

  public Comment createComment( String comment ) {
    ContentValues values = new ContentValues( );
    values.put( MySQLiteHelper.COLUMN_COMMENT, comment );
    long insertId = database.insert(
      MySQLiteHelper.TABLE_COMMENTS, null, values );
    Cursor cursor = database.query( MySQLiteHelper.TABLE_COMMENTS,
      allColumns, MySQLiteHelper.COLUMN_ID + " = " + insertId,
      null, null, null, null );
    cursor.moveToFirst( );
    return cursorToComment( cursor );
  }

adapter.add( comment );

Add the specified object at the end of the array.

src/main/java/com/example/wenchen/sqlitedemo/TestDatabase.java

package com.example.wenchen.sqlitedemo;

import java.util.List;
import java.util.Random;
import android.app.ListActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.ArrayAdapter;

public class TestDatabase extends ListActivity {
  private CommentsDataSource datasource;

  @Override
  public void onCreate( Bundle savedInstanceState ) {
    super.onCreate( savedInstanceState );
    setContentView( R.layout.main );

    datasource = new CommentsDataSource( this );
    datasource.open( );

    List<Comment> values = datasource.getAllComments( );

    // Use the SimpleCursorAdapter to show the elements in a ListView.
    ArrayAdapter<Comment> adapter = new ArrayAdapter<Comment>(
      this, android.R.layout.simple_list_item_1, values );
    setListAdapter( adapter );
  }

  // Will be called via the onClick attribute of the buttons in main.xml.
  public void onClick( View view ) {
    @SuppressWarnings( "unchecked" )
    ArrayAdapter<Comment> adapter = ( ArrayAdapter<Comment> ) getListAdapter( );
    Comment comment = null;
    int id = view.getId( );
    if ( id == R.id.add ) {
      String[ ] comments = new String[ ] { "Cool", "Very nice", "Hate it" };
      int nextInt = new Random( ).nextInt( 3 );
      // Save the new comment to the database.
      comment = datasource.createComment( comments[nextInt] );
      adapter.add( comment );
    }
    else if ( id == R.id.delete ) {
      if ( getListAdapter( ).getCount( ) > 0 ) {
        comment = (Comment) getListAdapter( ).getItem( 0 );
        datasource.deleteComment( comment );
        adapter.remove( comment );
      }
    }
    adapter.notifyDataSetChanged( );
  }

  @Override
  protected void onResume( ) {
    datasource.open( );
    super.onResume( );
  }

  @Override
  protected void onPause( ) {
    datasource.close( );
    super.onPause( );
  }
}