Content Provider基础
1.Content Provider为存储和获取数据提供了统一的接口。
2.Content Provider可以在不同的应用程序之间共享数据。
3.Android为常见的一些数据提供了ContentProvider(包括音频,视频,图片和通讯录等)。
Manifest中加入:
<provider android:name="ycitss.cp.FirstContentProvider"
android:authorities="ycitss.cp.FirstContentProvider" />
DatabaseHelper.java:
package ycitss.sqlite3.db; import ycitss.cp.FirstProviderMetaData; import android.content.Context; import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.SQLiteOpenHelper; import android.database.sqlite.SQLiteDatabase.CursorFactory;
//DatabaseHelper作为一个访问SQLite的助手类,提供两个方面的功能,
//第一,getReadableDatabase(),getWritableDatabase()可以获得SQLiteDatabse对象,通过该对象可以对数据库进行操作
//第二,提供了onCreate()和onUpgrade()两个回调函数,允许我们在创建和升级数据库时,进行自己的操作
public
class
DatabaseHelper
extends
SQLiteOpenHelper {
private
static
final
int
VERSION =
1
;
//在SQLiteOepnHelper的子类当中,必须有该构造函数
public
DatabaseHelper(Context context, String name, CursorFactory factory,
int
version) {
//必须通过super调用父类当中的构造函数
super
(context, name, factory, version);
// TODO Auto-generated constructor stub
}
public
DatabaseHelper(Context context,String name){
this
(context,name,VERSION);
}
public
DatabaseHelper(Context context,String name,
int
version){
this
(context, name,
null
,version);
}
//该函数是在第一次创建数据库的时候执行,实际上是在第一次得到SQLiteDatabse对象的时候,才会调用这个方法
@Override
public
void
onCreate(SQLiteDatabase db) {
// TODO Auto-generated method stub
System.out.println(
"create a Database"
);
//execSQL函数用于执行SQL语句
db.execSQL(
"create table user(id int,name varchar(20))"
);
}
@Override
public
void
onUpgrade(SQLiteDatabase db,
int
oldVersion,
int
newVersion) {
// TODO Auto-generated method stub
System.out.println(
"update a Database"
);
}
}
FirstProviderMetaData.java:
package ycitss.cp; import android.net.Uri; import android.provider.BaseColumns; public class FirstProviderMetaData { public static final String AUTHORITY = "ycitss.cp.FirstContentProvider"; //数据库名称 public static final String DATABASE_NAME = "FirstProvider.db"; //数据库的版本 public static final int DATABASE_VERSION = 1; //表名 public static final String USERS_TABLE_NAME = "users"; public static final class UserTableMetaData implements BaseColumns { //表名 public static final String TABLE_NAME = "users"; //访问该ContenProvider的URI public static final Uri CONTENT_URI = Uri.parse("content://" + AUTHORITY + "/users"); //该ContentProvider所返回的数据类型的定义 public static final String CONTENT_TYPE = "vnd.android.cursor.dir/vnd.firstprovider.user"; public static final String CONTENT_TYPE_ITEM = "vnd.android.cursor.item/vnd.firstprovider.user"; //列名 public static final String USER_NAME = "name"; //默认的排序方法 public static final String DEFAULT_SORT_ORDER = "_id desc"; } }
FirstContentProvider.java
package ycitss.cp; import java.util.HashMap; import ycitss.cp.FirstProviderMetaData.UserTableMetaData; import ycitss.sqlite3.db.DatabaseHelper; import android.content.ContentProvider; import android.content.ContentUris; import android.content.ContentValues; import android.content.UriMatcher; import android.database.Cursor; import android.database.SQLException; import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.SQLiteQueryBuilder; import android.net.Uri; import android.text.TextUtils; public class FirstContentProvider extends ContentProvider { public static final UriMatcher uriMatcher; public static final int INCOMING_USER_COLLECTION = 1; public static final int INCOMING_USER_SINGLE = 2; private DatabaseHelper dh; static { uriMatcher = new UriMatcher(UriMatcher.NO_MATCH); uriMatcher.addURI(FirstProviderMetaData.AUTHORITY, "users", INCOMING_USER_COLLECTION); uriMatcher.addURI(FirstProviderMetaData.AUTHORITY, "users/#", INCOMING_USER_SINGLE); } public static HashMap<String, String> userProjectionMap; static { userProjectionMap = new HashMap<String, String>(); userProjectionMap.put(UserTableMetaData._ID, UserTableMetaData._ID); userProjectionMap.put(UserTableMetaData.USER_NAME, UserTableMetaData.USER_NAME); } @Override public int delete(Uri arg0, String arg1, String[] arg2) { // TODO Auto-generated method stub System.out.println("delete..."); return 0; } //根据传入的URI,返回该URI所表示的数据类型 @Override public String getType(Uri uri) { System.out.println("getType..."); switch (uriMatcher.match(uri)) { case INCOMING_USER_COLLECTION: return UserTableMetaData.CONTENT_TYPE; case INCOMING_USER_SINGLE: return UserTableMetaData.CONTENT_TYPE_ITEM; default: throw new IllegalArgumentException("Unknow URI " + uri); } } /** * 该函数的返回值是一个Uri,这个Uri表示的是刚刚使用这个函数所传入的数据 * content://ycitss.cp.firstContentProivder/users/1 */ @Override public Uri insert(Uri uri, ContentValues values) { System.out.println("insert..."); SQLiteDatabase db = dh.getWritableDatabase(); long rowId = db.insert(UserTableMetaData.TABLE_NAME, null, values); if (rowId > 0) { Uri insertedUserUri = ContentUris.withAppendedId( UserTableMetaData.CONTENT_URI, rowId); //通知监听器,数据已经改变 getContext().getContentResolver().notifyChange(insertedUserUri, null); return insertedUserUri; } throw new SQLException("Failed to insert row into " + uri); } //是一个回调方法,所以说在ContentProvider创建的时候执行 @Override public boolean onCreate() { //打开数据库 dh = new DatabaseHelper(getContext(), FirstProviderMetaData.DATABASE_NAME); System.out.println("onCreate..."); return true; } @Override public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) { SQLiteQueryBuilder qb = new SQLiteQueryBuilder(); switch (uriMatcher.match(uri)) { case INCOMING_USER_COLLECTION: qb.setTables(UserTableMetaData.TABLE_NAME); qb.setProjectionMap(userProjectionMap); break; case INCOMING_USER_SINGLE: qb.setTables(UserTableMetaData.TABLE_NAME); qb.setProjectionMap(userProjectionMap); qb.appendWhere(UserTableMetaData._ID + "=" + uri.getPathSegments().get(1)); break; } String orderBy; if (TextUtils.isEmpty(sortOrder)) { orderBy = UserTableMetaData.DEFAULT_SORT_ORDER; } else { orderBy = sortOrder; } SQLiteDatabase db = dh.getWritableDatabase(); Cursor c = qb.query(db, projection, selection, selectionArgs, null, null, orderBy); c.setNotificationUri(getContext().getContentResolver(), uri); System.out.println("query..."); return c; } @Override public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) { System.out.println("update..."); return 0; } }
CPActivity.java:
package ycitss.cp; import ycitss.cp.FirstProviderMetaData.UserTableMetaData; import android.app.Activity; import android.content.ContentValues; import android.database.Cursor; import android.net.Uri; import android.os.Bundle; import android.view.View; import android.widget.Button; public class CPActivity extends Activity { /** Called when the activity is first created. */ private Button insertButton = null; private Button queryButton = null; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); insertButton = (Button) findViewById(R.id.insertButton); insertButton.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { ContentValues values = new ContentValues(); values.put(FirstProviderMetaData.UserTableMetaData.USER_NAME, "zhangsan"); Uri uri = getContentResolver().insert( FirstProviderMetaData.UserTableMetaData.CONTENT_URI, values); System.out.println("uri ---> " + uri.toString()); } }); queryButton = (Button) findViewById(R.id.queryButton); queryButton.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { Cursor c = getContentResolver().query( FirstProviderMetaData.UserTableMetaData.CONTENT_URI, null, null, null, null); while (c.moveToNext()) { System.out.println(c.getString(c .getColumnIndex(UserTableMetaData.USER_NAME))); } } }); } }
posted on 2013-06-23 23:32 leihupqrst 阅读(234) 评论(0) 编辑 收藏 举报