Android development-Database Application-SQLite OpenHelper-query and modify a single record

/* (Start of program header annotation)
* Copyright and version Declaration of the program
* Copyright (c) 2011, a student from the computer College of Yantai University
* All rights reserved.
* File name: Database Application-query and modify a single record
* Author: Lei hengxin
* Completion date: January 1, August 14, 2012
* Version No.: V1.0
* Description of tasks and Solutions
* Input description:
* Problem description:
* Program output:
* End the comment in the program Header
*/
 
In the "NotesDbAdapter" class, write the code for "querying a single record" and "modifying". The program is as follows:
[Java]
// Query single entry
Public Cursor get (long rowId) throws SQLException {
Cursor mCursor = db. query (true,
DATABASE_TABLE,
New String [] {KEY_ROWID, KEY_NOTE, KEY_CREATED },
KEY_ROWID + "=" + rowId,
Null, null );
If (mCursor! = Null ){
MCursor. moveToFirst ();
}
Return mCursor;
}
 
// Update
Public boolean update (long rowId, String note ){
ContentValues args = new ContentValues ();
Args. put (KEY_NOTE, note );
 
Return db. update (DATABASE_TABLE, args, KEY_ROWID + "=" + rowId, null)> 0;
}

 
The complete "NotesDbAdapter. java" program is as follows:
 
[Java]
Package com. demo. android. dummynote;
 
Import java. SQL. Date;
 
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. database. sqlite. SQLiteDatabase. CursorFactory;
 
Public class NotesDbAdapter {
Private static final String DATABASE_NAME = "notes. db ";
Private static final int DATABASE_VERSION = 1;
Private static final String DATABASE_TABLE = "notes ";
Private static final String DATABASE_CREATE = "creat table notes ("
+ "_ Id integer primary key," + "note TEXT," + "created INTEGER ,"
+ "Modified INTEGER" + ");";
 
Private static class DatabaseHelper extends SQLiteOpenHelper {
Public DatabaseHelper (Context context ){
Super (context, DATABASE_NAME, null, DATABASE_VERSION );
// TODO Auto-generated constructor stub
}
 
@ Override
Public void onCreate (SQLiteDatabase db ){
// TODO Auto-generated method stub
Db.exe cSQL (DATABASE_CREATE );
 
}
 
@ Override
Public void onUpgrade (SQLiteDatabase db, int oldVersion, int newVersion ){
// TODO Auto-generated method stub
Db.exe cSQL ("drop table if exists" + DATABASE_TABLE );
OnCreate (db );
}
}
 
Private Context mCtx = null;
Private DatabaseHelper dbHelper;
Private SQLiteDatabase db;
 
Public NotesDbAdapter (Context ctx ){
This. mCtx = ctx;
}
 
Public NotesDbAdapter open () throws SQLException {
DbHelper = new DatabaseHelper (mCtx );
Db = dbHelper. getWritableDatabase ();
Return this;
}
 
Public void close (){
DbHelper. close ();
}
 
Private static final String KEY_ROWID = "_ id ";
Static final String KEY_NOTE = "note ";
Private static final String KEY_CREATED = "created ";

// Get all entries
Public Cursor getall (){
Return db. query (DATABASE_TABLE, // Which table to Select
New String [] {KEY_ROWID, KEY_NOTE, KEY_CREATED}, // Which columns to return
Null, // WHERE clause
Null, // WHERE arguments
Null, // group by clause
Null, // HAVING clause
Null); // Order-by clause
 
}

// Add an entry
Public long create (String Note ){
Date now = new Date ();
ContentValues args = new ContentValues ();
Args. put (KEY_NOTE, Note );
Args. put (KEY_CREATED, now. getTime ());
 
Return db. insert (DATABASE_TABLE, null, args );
}
 
// Remove an entry
Public boolean delete (long rowID ){
Return db. delete (DATABASE_TABLE, KEY_ROWID + "=" + rowID, null)> 0;
}

// Query single entry
Public Cursor get (long rowId) throws SQLException {
Cursor mCursor = db. query (true,
DATABASE_TABLE,
New String [] {KEY_ROWID, KEY_NOTE, KEY_CREATED },
KEY_ROWID + "=" + rowId,
Null, null );
If (mCursor! = Null ){
MCursor. moveToFirst ();
}
Return mCursor;
}
 
// Update
Public boolean update (long rowId, String note ){
ContentValues args = new ContentValues ();
Args. put (KEY_NOTE, note );
 
Return db. update (DATABASE_TABLE, args, KEY_ROWID + "=" + rowId, null)> 0;
}
 
 
}
 
Note: The preceding program Date now = new Date (); has a small error. The Compiler prompts the following:
The Date () of the constructor is not defined;
 

 
But there is no parameter in the brackets of Date now = new Date () in the book. If you know what is going on, let me know in the comments.
 
By the way, write the "DummyNote" program:
[Java]
Package com. demo. android. dummynote;
 
Import android. app. ListActivity;
Import android. database. Cursor;
Import android. OS. Bundle;
Import android. view. Menu;
Import android. view. MenuItem;
Import android. widget. ArrayAdapter;
Import android. widget. ListAdapter;
Import android. widget. SimpleCursorAdapter;
Import android. content. Intent;
Import android. widget. ListView;
//////////////////////////////////////// ///////////////
Import android. app. ListActivity;
Import android. content. Intent;
Import android. database. Cursor;
Import android. OS. Bundle;
Import android. util. Log;
Import android. view. ContextMenu;
Import android. view. Menu;
Import android. view. MenuItem;
Import android. view. View;
Import android. view. ContextMenu. ContextMenuInfo;
Import android. widget. AdapterView;
Import android. widget. ListView;
Import android. widget. SimpleCursorAdapter;
 
 
//////////////////////////////////////// /////////////
 
Public class DummyNote extends ListActivity {
/** Called when the activity is first created .*/
@ Override
Public void onCreate (Bundle savedInstanceState ){
Super. onCreate (savedInstanceState );
SetContentView (R. layout. main );
// Tell the list view which view to display when the list is empty
GetListView (). setEmptyView (findViewById (R. id. empty ));
SetAdapter ();
}
Private String [] note_array = {
"Gasolin ",
"Crota ",
"Louk ",
"Magicion"
};
Private NotesDbAdapter mDbHelper;
Private Cursor mNotesCursor;
Private void setAdapter (){
MDbHelper = new NotesDbAdapter (this );
MDbHelper. open ();
FillData ();
}
Private void fillData (){
MNotesCursor = mDbHelper. getall ();
StartManagingCursor (mNotesCursor );

// Create an array to specify the field we want to display in the list
String [] from = new String [] {NotesDbAdapter. KEY_NOTE };

// An array of the fields we want to bind those fields
Int [] to = new int [] {android. R. id. text1 };

// Now create a simple cursor adapter
SimpleCursorAdapter adapter = new SimpleCursorAdapter (this,
Android. R. layout. simple_list_item_1, mNotesCursor, from, );
SetListAdapter (adapter );
}

Private int mNoteNumber = 1;
Protected static final int MENU_INSERT = Menu. FIRST;
Protected static final int MENU_DELETE = Menu. FIRST + 1;
Protected static final int MENU_MODIFY = Menu. FIRST + 1;

@ Override
Public boolean onCreateOptionsMenu (Menu menu ){
// TODO Auto-generated method stub
Super. onCreateOptionsMenu (menu );
Menu. add (0, MENU_INSERT, 0, "add notebook ");
Menu. add (0, MENU_DELETE, 0, "delete notebook ");
Return super. onCreateOptionsMenu (menu );
}
 
@ Override
Public boolean onOptionsItemSelected (MenuItem item ){
// TODO Auto-generated method stub
Switch (item. getItemId ()){
Case MENU_INSERT:
String noteName = "Note" + mNoteNumber ++;
MDbHelper. create (noteName );
FillData ();
Return true;
Case MENU_DELETE:
MDbHelper. delete (getListView (). getSelectedItemId ());
FillData ();
Return true;
}
Return super. onOptionsItemSelected (item );
}
 
}
Author: leihengxin