Android, sample3 , Create,open close SQLite DB

Source from:http://code.google.com/android/intro/tutorial-ex1.html



/*
* Copyright (C) 2008 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.android.demo.notepad1;
import android.app.ListActivity;
import android.database.Cursor;
import android.os.Bundle;
import android.view.Menu;
import android.view.Menu.Item;
import android.widget.SimpleCursorAdapter;
public class Notepadv1 extends ListActivity {
private int mNoteNumber = 1;
private NotesDbAdapter mDbHelper;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle icicle) {
//super.onCreate(icicle);
super.onCreate(icicle);
setContentView(R.layout.notepad_list);
mDbHelper = new NotesDbAdapter(this);
mDbHelper.open();
fillData();
}
public static final int INSERT_ID = Menu.FIRST; //Note: In strings.xml resource (under res/values), add a new string for menu_insert with text "Add Item" Add Item, then save the file
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// TODO Auto-generated method stub
// return super.onCreateOptionsMenu(menu);
boolean result = super.onCreateOptionsMenu(menu);
menu.add(0, INSERT_ID, R.string.menu_insert);
return result;
}
@Override
public boolean onOptionsItemSelected(Item item) {
// TODO Auto-generated method stub
//return super.onOptionsItemSelected(item);
switch (item.getId()) {
case INSERT_ID:
createNote();
return true;
}
return super.onOptionsItemSelected(item);
}
private void createNote() {
String noteName = "Note " + mNoteNumber++;
mDbHelper.createNote(noteName, "");
fillData();
}
private void fillData() {
// Get all of the notes from the database and create the item list
Cursor c = mDbHelper.fetchAllNotes();
startManagingCursor(c);
String[] from = new String[] { NotesDbAdapter.KEY_TITLE };
int[] to = new int[] { R.id.text1 };
// Now create an array adapter and set it to display using our row
SimpleCursorAdapter notes =
new SimpleCursorAdapter(this, R.layout.notes_row, c, from, to);
setListAdapter(notes);
}
}

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/*
* Copyright (C) 2008 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/ package com.google.android.demo.notepad1;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;

import java.io.FileNotFoundException;

/**
* Simple notes database access helper class. Defines the basic CRUD operations
* for the notepad example, and gives the ability to list all notes as well as
* retrieve or modify a specific note.
*
* This has been improved from the first version of this tutorial through the addition
* of better error handling and also using returning a Cursor instead of using
* a collection of inner classes (which is less scalable and not recommended).
*/
public class NotesDbAdapter {

public static final String KEY_TITLE="title";
public static final String KEY_BODY="body";
public static final String KEY_ROWID="_id";

/**
* Database creation sql statement
*/
private static final String DATABASE_CREATE =
"create table notes (_id integer primary key autoincrement, "
+ "title text not null, body text not null);";

private static final String DATABASE_NAME = "data";
private static final String DATABASE_TABLE = "notes";
private static final int DATABASE_VERSION = 2;

private SQLiteDatabase mDb;
private final Context mCtx;

/**
* Constructor - takes the context to allow the database to be opened/created
* @param ctx the Context within which to work
*/
public NotesDbAdapter(Context ctx) {
this.mCtx = ctx;
}

/**
* Open the notes database. If it cannot be opened, try to create a new instance of
* the database. If it cannot be created, throw an exception to signal the failure
* @return this (self reference, allowing this to be chained in an initialization call)
* @throws SQLException if the database could be neither opened or created
*/
public NotesDbAdapter open() throws SQLException {
try {
mDb = mCtx.openDatabase(DATABASE_NAME, null);
} catch (FileNotFoundException e) {
try {
mDb =
mCtx.createDatabase(DATABASE_NAME, DATABASE_VERSION, 0,
null);
mDb.execSQL(DATABASE_CREATE);
} catch (FileNotFoundException e1) {
throw new SQLException("Could not create database");
}
}
return this;
}

public void close() {
mDb.close();
}

/**
* Create a new note using the title and body provided. If the note is successfully created
* return the new rowId for that note, otherwise return a -1 to indicate failure.
* @param title the title of the note
* @param body the body of the note
* @return rowId or -1 if failed
*/
public long createNote(String title, String body) {
ContentValues initialValues = new ContentValues();
initialValues.put(KEY_TITLE, title);
initialValues.put(KEY_BODY, body);
return mDb.insert(DATABASE_TABLE, null, initialValues);
}

/**
* Delete the note with the given rowId
* @param rowId id of note to delete
* @return true if deleted, false otherwise
*/
public boolean deleteNote(long rowId) {
return mDb.delete(DATABASE_TABLE, KEY_ROWID + "=" + rowId, null) > 0;
}

/**
* Return a Cursor over the list of all notes in the database
* @return Cursor over all notes
*/
public Cursor fetchAllNotes() {
return mDb.query(DATABASE_TABLE, new String[] {
KEY_ROWID, KEY_TITLE, KEY_BODY}, null, null, null, null, null);
}

/**
* Return a Cursor positioned at the note that matches the given rowId
* @param rowId id of note to retrieve
* @return Cursor positioned to matching note, if found
* @throws SQLException if note could not be found/retrieved
*/
public Cursor fetchNote(long rowId) throws SQLException {
Cursor result = mDb.query(true, DATABASE_TABLE, new String[] {
KEY_ROWID, KEY_TITLE, KEY_BODY}, KEY_ROWID + "=" + rowId, null, null,
null, null);
if ((result.count() == 0) !result.first()) {
throw new SQLException("No note matching ID: " + rowId);
}
return result;
}

/**
* Update the note using the details provided. The note to be updated is specified using
* the rowId, and it is altered to use the title and body values passed in
* @param rowId id of note to update
* @param title value to set note title to
* @param body value to set note body to
* @return true if the note was successfully updated, false otherwise
*/
public boolean updateNote(long rowId, String title, String body) {
ContentValues args = new ContentValues();
args.put(KEY_TITLE, title);
args.put(KEY_BODY, body);
return mDb.update(DATABASE_TABLE, args, KEY_ROWID + "=" + rowId, null) > 0;
}
}

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