Android中ContentProvider跟ContentResolver使用入门_Android

Android中ContentProvider和ContentResolver使用入门

在Android中，我们的应用有的时候需要对外提供数据接口，可以有如下几种方法：1）AIDL 2）Broadcast 3）ContentProvider。
使用AIDL需要我们编写AIDL接口以及实现，而且对方也要有相应的接口描述，有点麻烦；使用Broadcast，我们不需要任何接口描述，只要协议文档就可以了，但是有点不好就是，这种方式不直接而且是异步的；使用ContentProvider我们不需要接口描述，只需要知道协议，同时这种方式是同步的，使用方便。下面是ContentProvider实现：

/**

?*?

?*/

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?{

[email protected]

????????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?};

????????}

[email protected]

????????protected?String[]?dropDBTables()?{

????????????//?TODO?Auto-generated?method?stub

????????????return?null;

????????}

[email protected]

????????protected?String?getDatabaseName()?{

????????????//?TODO?Auto-generated?method?stub

????????????return?DATABASE_NAME;

????????}

[email protected]

????????protected?int?getDatabaseVersion()?{

????????????//?TODO?Auto-generated?method?stub

????????????return?DB_VERSION;

????????}

[email protected]

????????protected?String?getTag()?{

????????????//?TODO?Auto-generated?method?stub

????????????return?TestContentProvider.class.getSimpleName();

????????}

????}

????/**

?????*?

?????*/

????public?TestContentProvider()?{

????????//?TODO?Auto-generated?constructor?stub

????????

????}

????/*

?????*?(non-Javadoc)

?????*?

[email protected]#delete(android.net.Uri,

?????*?java.lang.String,?java.lang.String[])

?????*/

[email protected]

????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)

?????*?

[email protected]#getType(android.net.Uri)

?????*/

[email protected]

????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)

?????*?

[email protected]#insert(android.net.Uri,

?????*?android.content.ContentValues)

?????*/

[email protected]

????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)

?????*?

[email protected]#onCreate()

?????*/

[email protected]

????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)

?????*?

[email protected]#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,

????????????????sortOrder);

????????Log.i("TestContentProvider",?"get?records");

????????c.setNotificationUri(getContext().getContentResolver(),?uri);

????????return?c;

????}

????/*

?????*?(non-Javadoc)

?????*?

[email protected]#update(android.net.Uri,

?????*?android.content.ContentValues,?java.lang.String,?java.lang.String[])

?????*/

[email protected]

????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。