NotePadProvider.java

package xiaohang.zhimeng;

import java.util.HashMap;

import xiaohang.zhimeng.NotePad.Notes;
import android.content.ContentProvider;
import android.content.ContentUris;
import android.content.ContentValues;
import android.content.Context;
import android.content.UriMatcher;
import android.content.res.Resources;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.database.sqlite.SQLiteQueryBuilder;
import android.net.Uri;
import android.text.TextUtils;

public class NotePadProvider extends ContentProvider{
	
	private static final String 		   TAG = "NotePadProvider";
	//���ݿ���
	private static final String 		   DATABASE_NAME = "note_pad.db";
	private static final int 			   DATABASE_VERSION = 2;
	//����
	private static final String 		   NOTES_TABLE_NAME = "notes";
	private static HashMap<String, String> sNotesProjectionMap;
	private static final int 			   NOTES = 1;
	private static final int 			   NOTE_ID = 2;
	private static final UriMatcher		   sUriMatcher;
	private DatabaseHelper mOpenHelper;
	//������SQL���
	private static final String 		   CREATE_TABLE="CREATE TABLE "
														+ NOTES_TABLE_NAME
														+ "(" + Notes._ID
														+ " INTEGER PRIMARY KEY, "
														+ Notes.TITLE
														+ " TEXT, "
														+ Notes.NOTE
														+ " TEXT, "
														+ Notes.CREATEDDATE
														+ " INTEGER, "
														+ Notes.MODIFIEDDATE
														+ " INTEGER" + ");";
	
	
	static{
		sUriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
		sUriMatcher.addURI(NotePad.AUTHORITY, "notes", NOTES);
		sUriMatcher.addURI(NotePad.AUTHORITY, "notes/#", NOTE_ID);
		
		sNotesProjectionMap = new HashMap<String, String>();
		sNotesProjectionMap.put(Notes._ID, Notes._ID);
		sNotesProjectionMap.put(Notes.TITLE, Notes.TITLE);
		sNotesProjectionMap.put(Notes.NOTE, Notes.NOTE);
		sNotesProjectionMap.put(Notes.CREATEDDATE, Notes.CREATEDDATE);
		sNotesProjectionMap.put(Notes.MODIFIEDDATE, Notes.MODIFIEDDATE);

	}
	
	private static class DatabaseHelper extends SQLiteOpenHelper{
		//���캯��-�������ݿ�
		DatabaseHelper(Context context){
			super(context, DATABASE_NAME, null, DATABASE_VERSION);
		}
		
		//������
		@Override
		public void onCreate(SQLiteDatabase db) {
			System.out.println("creat_table:  "+CREATE_TABLE);
			db.execSQL(CREATE_TABLE);
		}
		
		//�������ݿ�
		@Override
		public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
			db.execSQL("DROP TABLE IF EXISTS notes");
			onCreate(db);
		}
	}

	//ɾ������
	@Override
	public int delete(Uri uri, String selection, String[] selectionArgs) {
		SQLiteDatabase db = mOpenHelper.getWritableDatabase();
		int count;
		switch (sUriMatcher.match(uri)) {
		case NOTES:
			count = db.delete(NOTES_TABLE_NAME, selection, selectionArgs);
			break;
			
		case NOTE_ID:
			String noteId = uri.getPathSegments().get(1);
			count = db.delete(NOTES_TABLE_NAME, Notes._ID + "=" + noteId + (!TextUtils.isEmpty(selection) ? " AND (" + selection + ')' : ""), selectionArgs);
			break;
			
		default:
			throw new IllegalArgumentException("Unnown URI" + uri);
		}
		getContext().getContentResolver().notifyChange(uri, null);
		return count;
	}
	//������Զ����ͣ�����ʵ�ָ÷���
	@Override
	public String getType(Uri uri) {
		switch (sUriMatcher.match(uri)) {
		case NOTES:
			return Notes.CONTENT_TYPE;

		case NOTE_ID:
			return Notes.CONTENT_ITME_TYPE;
			
		default:
			throw new IllegalArgumentException("Unknown URI " + uri);
		}
	}

	//�������ݿ�
	@Override
	public Uri insert(Uri uri, ContentValues initialValues) {
		if (sUriMatcher.match(uri) != NOTES) {
			throw new IllegalArgumentException("Unknown URI " + uri);
		}
		ContentValues values;
		if (initialValues != null) {
			values = new ContentValues(initialValues);
		}else {
			values = new ContentValues();
		}
		//�����Ժ���Ϊ��λ��ϵͳ��ǰʱ��
		Long now = Long.valueOf(java.lang.System.currentTimeMillis());
		/**
		 * contaisKey()�ҵ��������жϴ��������Ǹ�ContentValues��û����Ӧ����ֵ
		 * ��Ϊ���ǵ�ContentValues��Ӧһ�����ݿ�ļ�¼
		 * */
		if (values.containsKey(NotePad.Notes.CREATEDDATE) == false) {
			values.put(NotePad.Notes.CREATEDDATE, now);
		}
		if (values.containsKey(NotePad.Notes.MODIFIEDDATE) == false) {
			values.put(NotePad.Notes.MODIFIEDDATE, now);
		}
		if (values.containsKey(NotePad.Notes.TITLE) == false) {
			//����һ��ȫ�ֹ������Դ����
			Resources r = Resources.getSystem();
			values.put(NotePad.Notes.TITLE, r.getString(android.R.string.unknownName));
		}
		if (values.containsKey(NotePad.Notes.NOTE) == false) {
			values.put(NotePad.Notes.NOTE, "");
		}
		SQLiteDatabase db = mOpenHelper.getWritableDatabase();
		long rowId = db.insert(NOTES_TABLE_NAME, Notes.NOTE, values);
		if (rowId > 0) {
			Uri noteUri = ContentUris.withAppendedId(NotePad.Notes.CONTENT_URI, rowId);
			getContext().getContentResolver().notifyChange(noteUri, null);
			return noteUri;
		}
		throw new SQLException("Failed to insert row into" + uri);
	}
	
	//��Content Provider����ʱ������
	@Override
	public boolean onCreate() {
		mOpenHelper = new DatabaseHelper(getContext());
		return true;
	}
	
	//��ѯ����  ����ѯ�������� Cursor �������ʽ����
	@Override
	public Cursor query(Uri uri, String[] projection, String selection,
			String[] selectionArgs, String sortOrder) {
		SQLiteQueryBuilder qb = new SQLiteQueryBuilder();
		switch (sUriMatcher.match(uri)) {
		case NOTES:
			qb.setTables(NOTES_TABLE_NAME);
			qb.setProjectionMap(sNotesProjectionMap);
			break;
			
		case NOTE_ID:
			qb.setTables(NOTES_TABLE_NAME);
			qb.setProjectionMap(sNotesProjectionMap);
			qb.appendWhere(Notes._ID + "=" + uri.getPathSegments().get(1));
			break;
			
		default:
			throw new IllegalArgumentException("Unknown URI " + uri);
		}
		String orderBy;
		//����true������ַ���Ϊ�ջ�0����
		if (TextUtils.isEmpty(sortOrder)) {
			orderBy = NotePad.Notes.DEFAULT_SORT_ORDER;
		}else {
			orderBy = sortOrder;
		}
		SQLiteDatabase db = mOpenHelper.getReadableDatabase();
		Cursor c = qb.query(db, projection, selection, selectionArgs, null, null, orderBy);
		//����ΪCursor����ע��һ���۲����ݱ仯��URI
		c.setNotificationUri(getContext().getContentResolver(), uri);
		return c;
	}

	//��������
	@Override
	public int update(Uri uri, ContentValues values, String selection,
			String[] selectionArgs) {
		SQLiteDatabase db = mOpenHelper.getWritableDatabase();
		int count;
		switch (sUriMatcher.match(uri)) {
		case NOTES:
			count = db.update(NOTES_TABLE_NAME, values, selection, selectionArgs);
			break;
		
		case NOTE_ID:
			String noteId = uri.getPathSegments().get(1);
			count = db.update(NOTES_TABLE_NAME, values, Notes._ID + "=" + noteId + (!TextUtils.isEmpty(selection) ? " AND (" + selection + ')' : ""), selectionArgs);
			break;
			
		default:
			throw new IllegalArgumentException("Unknow URI " + uri);
		}
		
		return count;
	}
}