contentprovider

最新推荐文章于 2024-08-01 09:28:45 发布

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本文详细介绍了一个具体的Android ContentProvider实现案例，包括如何通过继承ContentProvider来创建自定义的数据提供者，如何处理基本的CRUD操作，并展示了如何使用UriMatcher进行URI匹配。

Android中contentprovider，在编写extends contentprovider类时，需注意常量名的大小写。

举例如下：

package com.amaker.provider;

import java.util.HashMap;

import android.content.ContentProvider;
import android.content.ContentUris;
import android.content.ContentValues;
import android.content.UriMatcher;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteQueryBuilder;
import android.net.Uri;
import android.text.TextUtils;

public class VideoChanelProvider extends ContentProvider {
private DBHelper dbHelper;
// Uri��
private static HashMap<String, String> videochanelProjectionMap;
private static final UriMatcher sUriMatcher;
private final static int VIDEOCHANEL=1;
private final static int VIDEOCHANEL_ID=2;
static {
// Uriƥ�乤��
sUriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
sUriMatcher.addURI(VideoChanel.AUTHORITY, "videoChanel", VIDEOCHANEL);
sUriMatcher.addURI(VideoChanel.AUTHORITY, "videoChanel/#", VIDEOCHANEL_ID);
// ʵ��ѯ�м��
videochanelProjectionMap= new HashMap<String, String>();
// ��Ӳ�ѯ��
videochanelProjectionMap.put(VideoChanel.VIDEOCHANEL_ID, VideoChanel.VIDEOCHANEL_ID);
videochanelProjectionMap.put(VideoChanel. VIDEOCHANELNAME , VideoChanel. VIDEOCHANELNAME);

}
@Override
public boolean onCreate() {
// TODO Auto-generated method stub
dbHelper = new DBHelper(getContext());
return true;
}

@Override
public Cursor query(Uri uri, String[] projection, String selection,
String[] selectionArgs, String sortOrder) {
// TODO Auto-generated method stub
SQLiteQueryBuilder qb = new SQLiteQueryBuilder();
switch (sUriMatcher.match(uri)) {
// ��ѯ��
case VIDEOCHANEL:
qb.setTables(DBHelper.TABLES_VideoChanelTbl);
qb.setProjectionMap(videochanelProjectionMap);
break;
// ��ID��ѯ
case VIDEOCHANEL_ID:
qb.setTables(DBHelper.TABLES_VideoChanelTbl);
qb.setProjectionMap(videochanelProjectionMap);
qb.appendWhere( VideoChanel.VIDEOCHANEL_ID + "=" + uri.getPathSegments().get(1));
break;
default:
throw new IllegalArgumentException("Uri�� " + uri);
}

// ʹ��Ĭ��
String orderBy;
if (TextUtils.isEmpty(sortOrder)) {
orderBy = Video.DEFAULT_SORT_ORDER;
} else {
orderBy = sortOrder;
}

// ��ݿ�ʵ��
SQLiteDatabase db = dbHelper.getReadableDatabase();
// ��α꼯��
Cursor c = qb.query(db, projection, selection, selectionArgs, null, null, orderBy);
c.setNotificationUri(getContext().getContentResolver(), uri);
return c;

}

@Override
public String getType(Uri uri) {
// TODO Auto-generated method stub
return null;
}

@Override
public Uri insert(Uri uri, ContentValues values) {
// TODO Auto-generated method stub
SQLiteDatabase db = dbHelper.getWritableDatabase();
// ��ݣ��ID
long rowId = db.insert(DBHelper.TABLES_VideoChanelTbl,null, values);
// ��ɹ��uri
if (rowId > 0) {
Uri empUri = ContentUris.withAppendedId(Video.CONTENT_URI, rowId);
getContext().getContentResolver().notifyChange(empUri, null);
return empUri;
}
return null;
}

@Override
public int delete(Uri uri, String selection, String[] selectionArgs) {
// TODO Auto-generated method stub
SQLiteDatabase db = dbHelper.getWritableDatabase();
db.delete(DBHelper.TABLES_VideoChanelTbl, null, null);
return 0;
}

@Override
public int update(Uri uri, ContentValues values, String selection,
String[] selectionArgs) {
// TODO Auto-generated method stub
return 0;
}

}