Invata Sistemul de Operare Android – Partea 11

database.query(dbName, 
	int[] columnNames, 
	String whereClause, 
        String[] selectionArgs, 
        String[] groupBy, 
        String[] having, 
        String[] orderBy);

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
 
public class MySQLiteHelper extends SQLiteOpenHelper {
 
	public static final String TABLE_COMMENTS = "comments";
	public static final String COLUMN_ID = "_id";
	public static final String COLUMN_COMMENT = "comment";
 
	private static final String DATABASE_NAME = "commments.db";
	private static final int DATABASE_VERSION = 1;
 
	// Database creation sql statement
	private static final String DATABASE_CREATE = "create table "
			+ TABLE_COMMENTS + "( " + COLUMN_ID
			+ " integer primary key autoincrement, " + COLUMN_COMMENT
			+ " text not null);";
 
	public MySQLiteHelper(Context context) {
		super(context, DATABASE_NAME, null, DATABASE_VERSION);
	}
 
	@Override
	public void onCreate(SQLiteDatabase database) {
		database.execSQL(DATABASE_CREATE);
	}
 
	@Override
	public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
		Log.w(MySQLiteHelper.class.getName(),
				"Upgrading database from version " + oldVersion + " to "
						+ newVersion + ", which will destroy all old data");
		db.execSQL("DROP TABLE IF EXISTS" + TABLE_COMMENTS);
		onCreate(db);
	}
 
}

public class Comment {
	private long id;
	private String comment;
 
	public long getId() {
		return id;
	}
 
	public void setId(long id) {
		this.id = id;
	}
 
	public String getComment() {
		return comment;
	}
 
	public void setComment(String comment) {
		this.comment = comment;
	}
 
	// Will be used by the ArrayAdapter in the ListView
	@Override
	public String toString() {
		return comment;
	}
}

import java.util.ArrayList;
import java.util.List;
 
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
 
public class CommentsDataSource {
 
	// Database fields
	private SQLiteDatabase database;
	private MySQLiteHelper dbHelper;
	private String[] allColumns = { MySQLiteHelper.COLUMN_ID,
			MySQLiteHelper.COLUMN_COMMENT };
 
	public CommentsDataSource(Context context) {
		dbHelper = new MySQLiteHelper(context);
	}
 
	public void open() throws SQLException {
		database = dbHelper.getWritableDatabase();
	}
 
	public void close() {
		dbHelper.close();
	}
 
	public Comment createComment(String comment) {
		ContentValues values = new ContentValues();
		values.put(MySQLiteHelper.COLUMN_COMMENT, comment);
		long insertId = database.insert(MySQLiteHelper.TABLE_COMMENTS, null,
				values);
		// To show how to query
		Cursor cursor = database.query(MySQLiteHelper.TABLE_COMMENTS,
				allColumns, MySQLiteHelper.COLUMN_ID + " = " + insertId, null,
				null, null, null);
		cursor.moveToFirst();
		return cursorToComment(cursor);
	}
 
	public void deleteComment(Comment comment) {
		long id = comment.getId();
		System.out.println("Comment deleted with id: " + id);
		database.delete(MySQLiteHelper.TABLE_COMMENTS, MySQLiteHelper.COLUMN_ID
				+ " = " + id, null);
	}
 
	public List<Comment> getAllComments() {
		List<Comment> comments = new ArrayList<Comment>();
		Cursor cursor = database.query(MySQLiteHelper.TABLE_COMMENTS,
				allColumns, null, null, null, null, null);
		cursor.moveToFirst();
		while (!cursor.isAfterLast()) {
			Comment comment = cursorToComment(cursor);
			comments.add(comment);
			cursor.moveToNext();
		}
		// Make sure to close the cursor
		cursor.close();
		return comments;
	}
 
	private Comment cursorToComment(Cursor cursor) {
		Comment comment = new Comment();
		comment.setId(cursor.getLong(0));
		comment.setComment(cursor.getString(1));
		return comment;
	}
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >
 
    <LinearLayout
        android:id="@+id/group"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" >
 
        <Button
            android:id="@+id/add"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Add New" 
            android:onClick="onClick"/>
 
        <Button
            android:id="@+id/delete"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Delete First" 
            android:onClick="onClick"/>
 
    </LinearLayout>
 
    <ListView
        android:id="@android:id/list"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="@string/hello" />
 
</LinearLayout>

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 TestDatabaseActivity 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;
		switch (view.getId()) {
		case 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);
			break;
		case R.id.delete:
			if (getListAdapter().getCount() > 0) {
				comment = (Comment) getListAdapter().getItem(0);
				datasource.deleteComment(comment);
				adapter.remove(comment);
			}
			break;
		}
		adapter.notifyDataSetChanged();
	}
 
	@Override
	protected void onResume() {
		datasource.open();
		super.onResume();
	}
 
	@Override
	protected void onPause() {
		datasource.close();
		super.onPause();
	}
 
}