Android中ContentProvider跟ContentResolver使用入门

Android中ContentProvider和ContentResolver使用入门

/**
?*?
?*/
package?com.backgroundservice;

import?android.content.ContentProvider;
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.util.Log;

/**
?*?TODO
?*?
?*?@author?tianlu
?*?@version?1.0?Create?At?:?2010-2-18?下午01:58:39
?*/
public?class?TestContentProvider?extends?ContentProvider?{
????private?SQLiteDatabase?mDb;
????private?DatabaseHelper?mDbHelper?=?null;
????private?static?final?String?DATABASE_NAME?=?"rssitems.db";
????private?static?final?String?DATABASE_TABLE_NAME?=?"rssItems";
????private?static?final?int?DB_VERSION?=?1;
????private?static?final?int?ALL_MESSAGES?=?1;
????private?static?final?int?SPECIFIC_MESSAGE?=?2;

????//?Set?up?our?URL?matchers?to?help?us?determine?what?an
????//?incoming?URI?parameter?is.
????private?static?final?UriMatcher?URI_MATCHER;
????static?{
????????URI_MATCHER?=?new?UriMatcher(UriMatcher.NO_MATCH);
????????URI_MATCHER.addURI("test",?"item",?ALL_MESSAGES);
????????URI_MATCHER.addURI("test",?"item/#",?SPECIFIC_MESSAGE);
????}

????//?Here's?the?public?URI?used?to?query?for?RSS?items.
????public?static?final?Uri?CONTENT_URI?=?Uri
????????????.parse("content://test/item");

????//?Here?are?our?column?name?constants,?used?to?query?for?field?values.
????public?static?final?String?ID?=?"_id";
????public?static?final?String?NAME?=?"NAME";
????public?static?final?String?VALUE?=?"VALUE";
????public?static?final?String?DEFAULT_SORT_ORDER?=?ID?+?"?DESC";

????private?static?class?DatabaseHelper?extends?AbstractDatabaseHelper?{

????????@Override
????????protected?String[]?createDBTables()?{
????????????//?TODO?Auto-generated?method?stub
????????????String?sql?=?"CREATE?TABLE?"?+?DATABASE_TABLE_NAME?+?"("?+?ID
????????????????????+?"?INTEGER?PRIMARY?KEY?AUTOINCREMENT,?"?+?NAME?+?"?TEXT,"
????????????????????+?VALUE?+?"?TEXT);";
????????????return?new?String[]?{?sql?};
????????}

????????@Override
????????protected?String[]?dropDBTables()?{
????????????//?TODO?Auto-generated?method?stub
????????????return?null;
????????}

????????@Override
????????protected?String?getDatabaseName()?{
????????????//?TODO?Auto-generated?method?stub
????????????return?DATABASE_NAME;
????????}

????????@Override
????????protected?int?getDatabaseVersion()?{
????????????//?TODO?Auto-generated?method?stub
????????????return?DB_VERSION;
????????}

????????@Override
????????protected?String?getTag()?{
????????????//?TODO?Auto-generated?method?stub
????????????return?TestContentProvider.class.getSimpleName();
????????}

????}

????/**
?????*?
?????*/
????public?TestContentProvider()?{
????????//?TODO?Auto-generated?constructor?stub
????????
????}

????/*
?????*?(non-Javadoc)
?????*?
?????*?@see?android.content.ContentProvider#delete(android.net.Uri,
?????*?java.lang.String,?java.lang.String[])
?????*/
????@Override
????public?int?delete(Uri?uri,?String?selection,?String[]?selectionArgs)?{
????????//?NOTE?Argument?checking?code?omitted.?Check?your?parameters!
????????int?rowCount?=?mDb.delete(DATABASE_TABLE_NAME,?selection,?selectionArgs);

????????//?Notify?any?listeners?and?return?the?deleted?row?count.
????????getContext().getContentResolver().notifyChange(uri,?null);
????????return?rowCount;
????}

????/*
?????*?(non-Javadoc)
?????*?
?????*?@see?android.content.ContentProvider#getType(android.net.Uri)
?????*/
????@Override
????public?String?getType(Uri?uri)?{
????????switch?(URI_MATCHER.match(uri))?{
????????case?ALL_MESSAGES:
????????????return?"vnd.android.cursor.dir/rssitem";?//?List?of?items.
????????case?SPECIFIC_MESSAGE:
????????????return?"vnd.android.cursor.item/rssitem";?//?Specific?item.
????????default:
????????????return?null;
????????}
????}

????/*
?????*?(non-Javadoc)
?????*?
?????*?@see?android.content.ContentProvider#insert(android.net.Uri,
?????*?android.content.ContentValues)
?????*/
????@Override
????public?Uri?insert(Uri?uri,?ContentValues?values)?{
????????//?NOTE?Argument?checking?code?omitted.?Check?your?parameters!?Check?that
????????//?your?row?addition?request?succeeded!

???????long?rowId?=?-1;
???????rowId?=?mDb.insert(DATABASE_TABLE_NAME,?NAME,?values);
???????Uri?newUri?=?Uri.withAppendedPath(CONTENT_URI,?""+rowId);
???????Log.i("TestContentProvider",?"saved?a?record?"?+?rowId?+?"?"?+?newUri);
???????//?Notify?any?listeners?and?return?the?URI?of?the?new?row.
???????getContext().getContentResolver().notifyChange(CONTENT_URI,?null);
???????return?newUri;
????}

????/*
?????*?(non-Javadoc)
?????*?
?????*?@see?android.content.ContentProvider#onCreate()
?????*/
????@Override
????public?boolean?onCreate()?{
????????//?TODO?Auto-generated?method?stub
????????try
????????{
????????????mDbHelper?=?new?DatabaseHelper();
????????????mDbHelper.open(getContext());
????????????mDb?=?mDbHelper.getMDb();
????????}catch(Exception?e){
????????????e.printStackTrace();
????????}
????????return?true;
????}

????/*
?????*?(non-Javadoc)
?????*?
?????*?@see?android.content.ContentProvider#query(android.net.Uri,
?????*?java.lang.String[],?java.lang.String,?java.lang.String[],
?????*?java.lang.String)
?????*/
????public?Cursor?query(Uri?uri,?String[]?projection,?String?selection,
????????????String[]?selectionArgs,?String?sortOrder)?{
????????//?We?won't?bother?checking?the?validity?of?params?here,?but?you?should!

????????//?SQLiteQueryBuilder?is?the?helper?class?that?creates?the
????????//?proper?SQL?syntax?for?us.
????????SQLiteQueryBuilder?qBuilder?=?new?SQLiteQueryBuilder();

????????//?Set?the?table?we're?querying.
????????qBuilder.setTables(DATABASE_TABLE_NAME);

????????//?If?the?query?ends?in?a?specific?record?number,?we're
????????//?being?asked?for?a?specific?record,?so?set?the
????????//?WHERE?clause?in?our?query.
????????if((URI_MATCHER.match(uri))?==?SPECIFIC_MESSAGE){
????????????qBuilder.appendWhere("_id="?+?uri.getLastPathSegment());
????????????Log.i("TestContentProvider",?"_id="?+??uri.getLastPathSegment());
????????}


????????//?Make?the?query.
????????Cursor?c?=?qBuilder.query(mDb,
????????????????projection,
????????????????selection,
????????????????selectionArgs,
????????????????null,
????????????????null,
????????????????sortOrder);
????????Log.i("TestContentProvider",?"get?records");
????????c.setNotificationUri(getContext().getContentResolver(),?uri);
????????return?c;
????}

????/*
?????*?(non-Javadoc)
?????*?
?????*?@see?android.content.ContentProvider#update(android.net.Uri,
?????*?android.content.ContentValues,?java.lang.String,?java.lang.String[])
?????*/
????@Override
????public?int?update(Uri?uri,?ContentValues?values,?String?selection,
????????????String[]?selectionArgs)?{
????????//?NOTE?Argument?checking?code?omitted.?Check?your?parameters!
????????int?updateCount?=?mDb.update(DATABASE_TABLE_NAME,?values,?selection,?selectionArgs);

????????//?Notify?any?listeners?and?return?the?updated?row?count.
????????getContext().getContentResolver().notifyChange(uri,?null);
????????return?updateCount;
????}

}
配置文件如下：
????????<provider?android:name="TestContentProvider"
????????????android:authorities="test">
????????</provider>在客户端中可以使用如下方法进行调用：
????????????????ContentValues?values?=?new?ContentValues();
????????????????values.put(TestContentProvider.NAME,?"testname1");
????????????????values.put(TestContentProvider.VALUE,?"testvalu1e");
????????????????Uri?newAddUri?=?TestActivity.this.getContentResolver().insert(TestContentProvider.CONTENT_URI,?values);
????????????????Cursor?c?=?TestActivity.this.managedQuery(newAddUri,?new?String[]{TestContentProvider.NAME},?null,?null,?null);
????????????????Log.i("TestActivity",?""?+?c.getCount());
????????????????if(c.moveToNext())
????????????????{
????????????????????Log.i("TestActivity",?c.getString(0));
????????????????}上面的代码是先进行插入，然后进行查询并打印。就是如此简单，所有的应用如果需要都可以对外方便的提供数据接口，同时其他应用也可以很方便的进行调用。