Android记事本notepad源代码

/* * 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.android.demo.notepad3; import android.content.ContentValues; import android.content.Context; import android.database.Cursor; import android.database.SQLException; import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.SQLiteOpenHelper; import android.util.Log; /** * 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"; private static final String TAG = "NotesDbAdapter"; private DatabaseHelper mDbHelper; private SQLiteDatabase mDb; /** * 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 final Context mCtx; private static class DatabaseHelper extends SQLiteOpenHelper { DatabaseHelper(Context context) { super(context, DATABASE_NAME, null, DATABASE_VERSION); } @Override public void onCreate(SQLiteDatabase db) { db.execSQL(DATABASE_CREATE); } @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { Log.w(TAG, "Upgrading database from version " + oldVersion + " to " + newVersion + ", which will destroy all old data"); db.execSQL("DROP TABLE IF EXISTS notes"); onCreate(db); } } /** * 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 { mDbHelper = new DatabaseHelper(mCtx); mDb = mDbHelper.getWritableDatabase(); return this; } public void close() { mDbHelper.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 mCursor = mDb.query(true, DATABASE_TABLE, new String[] {KEY_ROWID, KEY_TITLE, KEY_BODY}, KEY_ROWID + "=" + rowId, null, null, null, null, null); if (mCursor != null) { mCursor.moveToFirst(); } return mCursor; } /** * 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; } }