1、安卓高级应用 多媒体和Service第六章 安卓高级应用在Android中,熟练使用4大组件,对理解Andriod程序,开发高级功能有着至关重要的作用。本章将会逐一讲解Activity以外的3大组件:ContentProvider,BroadcastReceiver和Service的原理及应用,并且介绍以它们为基础开发的多媒体和电话短信等系统应用。6.1 ContentProvider6.1.1 ContentProvider简介ContentProvider是Android的四大组件之一,用于保存和检索数据,是Android系统中不同应用程序之间共享数据的接口。Android系统中对一些常见
2、的公用数据提供了ContentProvider接口,例如视频,音频,图像,个人通信信息等,都定义在android.provider包下。若开发着想将自己的程序的数据公开给其他应用程序使用,有两种方法:一种是定义自己的ContentProvider子类,另一种是将当前的数据添加到已有的ContentProvider中,我们下面主要讨论第一种情况。6.1.2 使用ContentProvider实现通过ContentProvider对外共享数据,需要2个步骤:1)继承ContentProvider并重写下面方法public class MyProvider extends ContentProvid
3、er public boolean onCreate() public Uri insert(Uri uri, ContentValues values) public int delete(Uri uri, String selection, String selectionArgs) public int update(Uri uri, ContentValues values, String selection, String selectionArgs) public Cursor query(Uri uri, String projection, String selection,
4、String selectionArgs, String sortOrder) public String getType(Uri uri) 这其中除了常用的增删改查方法外,onCreate方法用于启动时初始化ContentProvider,getType方法用于返回Uri指定的ContentProvider中的数据的MIME类型。2)在Manifest文件中注册Provider 为了能让其他应用找到该ContentProvider,ContentProvider采用了authorities(主机名/域名)对它进行唯一标识,你可以把 ContentProvider看作是一个网站,authori
5、ties 就是他的域名。URI介绍ContentProvider通过URI来共享数据。URI是一个通用资源标识符,它的构成如图6-1所示:图6-1 URI的组成从上图可见,一般URI由4部分构成:1) sheme:无法改变的标准前缀2) 主机名或authority:ContentProvider的唯一标示,在Manifes中声明3) 路径:可以理解为要操作的数据中表的名字4) ID:需要获取的记录的ID,如果没有则表示返回全部记录UriMatcherAndroid系统提供了UriMatcher类来对URI进行匹配。使用步骤如下:1) 首先创建UriMatcher类2) 然后通过addURI方法
6、增加需要匹配的路径,并给每个路径标记一个匹配码3) 最后通过match方法进行匹配,返回匹配码代码片段如下: private static UriMatcher matcher = new UriMatcher(UriMatcher.NO_MATCH); private static final int CONTACTS = 1;/ 匹配码1 private static final int CONTACT = 2;/ 匹配码2 private static final String TABLENAME = person; static matcher.addURI(com.spl.mypro
7、vider, person, CONTACTS); matcher.addURI(com.spl.myprovider, person/#, CONTACT); Override public int delete(Uri uri, String selection, String selectionArgs) switch (matcher.match(uri) case CONTACTS: / 执行相应操作 case CONTACT: / 执行相应操作 default: throw new IllegalArgumentException(URI + uri + 无法解析!); 上面代码中
8、出现的“#”为通配符,代表任意数字,另外还可以使用通配符“*”来代表任意文本。ContentResolver介绍其他应用程序要想访问ContentProvider中的数据,就需要通过ContentResolver对象。ContantResolver提供的方法和ContentProvider相对应,也有增删改查这4个方法。每个Activity都有一个ContentResolver对象,可以通过getContentResolver方法获取到。下面的实例展示了如何使用ContentProvider共享数据,以及如何让其他应用获取到ContentProvider中的数据。该实例有两个应用组成:第1个应
9、用SQLiteDemo本质上是一个数据库应用,它维护一个数据表person,并通过MyProvider类对外共享了这张表的数据;第2个应用ContentResolverDemo只包含一个Activity,通过ContentResolver来访问person表中的数据。SQLiteDemo中的MyProvider.java的代码如下:package spl.db.contentprovider;import spl.db.DBHelper;import android.content.ContentProvider;import android.content.ContentUris;impor
10、t android.content.ContentValues;import android.database.Cursor;import android.database.sqlite.SQLiteDatabase;import .Uri;import android.content.UriMatcher;public class MyProvider extends ContentProvider private DBHelper helper; private static UriMatcher matcher = new UriMatcher(UriMatcher.NO_MATCH);
11、 private static final int CONTACTS = 1;/ 匹配码1 private static final int CONTACT = 2;/ 匹配码2 private static final String TABLENAME = person; static matcher.addURI(com.spl.myprovider, person, CONTACTS); matcher.addURI(com.spl.myprovider, person/#, CONTACT); Override public boolean onCreate() helper = ne
12、w DBHelper(getContext(); return true; Override public Uri insert(Uri uri, ContentValues values) SQLiteDatabase sqLiteDatabase = helper.getWritableDatabase(); switch (matcher.match(uri) case CONTACTS: long id = sqLiteDatabase.insert(TABLENAME, name, values); Uri insertUri = ContentUris.withAppendedId
13、(uri, id); return insertUri; default: throw new IllegalArgumentException(URI + uri + 无法解析!); Override public int delete(Uri uri, String selection, String selectionArgs) SQLiteDatabase sqLiteDatabase = helper.getWritableDatabase(); int rowNum = 0; switch (matcher.match(uri) case CONTACTS: rowNum = sq
14、LiteDatabase.delete(TABLENAME, selection, selectionArgs); return rowNum; case CONTACT: long id = ContentUris.parseId(uri); String whereClause = _id= + id; if (selection != null) whereClause += and + selection; rowNum = sqLiteDatabase.delete(TABLENAME, whereClause, selectionArgs); return rowNum; defa
15、ult: throw new IllegalArgumentException(URI + uri + 无法解析!); Override public int update(Uri uri, ContentValues values, String selection, String selectionArgs) SQLiteDatabase sqLiteDatabase = helper.getWritableDatabase(); int rowNum = 0; switch (matcher.match(uri) case CONTACTS: rowNum = sqLiteDatabas
16、e.update(TABLENAME, values, selection, selectionArgs); return rowNum; case CONTACT: long id = ContentUris.parseId(uri); String whereClause = _id= + id; if (selection != null) whereClause += and + selection; rowNum = sqLiteDatabase.update(TABLENAME, values, whereClause, selectionArgs); return rowNum;
17、 default: throw new IllegalArgumentException(URI + uri + 无法解析!); Override public Cursor query(Uri uri, String projection, String selection, String selectionArgs, String sortOrder) SQLiteDatabase db = helper.getReadableDatabase(); switch (matcher.match(uri) case CONTACTS: return db.query(TABLENAME, p
18、rojection, selection, selectionArgs, null, null, sortOrder); case CONTACT: long id = ContentUris.parseId(uri); String whereClause = _id= + id; if (selection != null) whereClause += and + selection; return db.query(TABLENAME, projection, whereClause, selectionArgs, null, null, sortOrder); default: th
19、row new IllegalArgumentException(URI + uri + 无法解析!); Override public String getType(Uri uri) switch (matcher.match(uri) case CONTACTS: return vnd.android.cursor.dir/person; case CONTACT: return vnd.android.cursor.item/person; default: throw new IllegalArgumentException(URI + uri + 无法解析!); SQLiteDemo
20、中的DBHelper.java的代码如下:package spl.db;import android.content.Context;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteOpenHelper;public class DBHelper extends SQLiteOpenHelper private static final String DATABASE_NAME = contactinfo.db; private static final int VERSION
21、 = 1; public DBHelper(Context context) super(context, DATABASE_NAME, null, VERSION); / TODO Auto-generated constructor stub Override public void onCreate(SQLiteDatabase db) / TODO Auto-generated method stub db.execSQL(CREATE TABLE person(_id INTEGER PRIMARY KEY autoincrement,name varchar(20),age INT
22、EGER); Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) / TODO Auto-generated method stub SQLiteDemo的Manifest文件中有关Provider注册的代码如下: ContentResolverDemo中的主Activity代码如下package .jbit.activity;import android.app.Activity;import android.content.ContentResolver;import andro
23、id.content.ContentUris;import android.content.ContentValues;import android.database.Cursor;import .Uri;import android.os.Bundle;import android.view.View;import android.widget.ListView;import android.widget.SimpleCursorAdapter;public class ResolverActivity extends Activity /* Called when the activity
24、 is first created. */ Override public void onCreate(Bundle savedInstanceState) super.onCreate(savedInstanceState); setContentView(R.layout.main); public void BtnOnClick(View view) ContentResolver resolver = this.getContentResolver(); Uri uri = Uri.parse(content:/com.spl.myprovider/person); switch (v
25、iew.getId() / 增加一条记录 case R.id.button1: ContentValues values = new ContentValues(); values.put(name, lilei); values.put(age, 13); resolver.insert(uri, values); break; / 删除一条记录 case R.id.button2: Uri deleteIdUri = ContentUris.withAppendedId(uri,11); resolver.delete(deleteIdUri, null, null); break; /
26、修改一条记录 case R.id.button3: ContentValues values = new ContentValues(); values.put(name, wanggang); Uri updateUri = ContentUris.withAppendedId(uri, 5); resolver.update(updateUri, values, null, null); break; / 查询并显示所有记录 case R.id.button4: Cursor cursor = resolver.query(uri, null, null, null, null); Sim
27、pleCursorAdapter adapter = new SimpleCursorAdapter( this, R.layout.dataview_layout, cursor, new String _id,name, age, new int R.id.contact_id, R.id.contact_name, R.id.contact_age); ListView listView = (ListView) findViewById(R.id.listView1); listView.setAdapter(adapter); break; ContentResolverDemo中的main.xml代码如下 Button android:id=+id/button2 android:layout_width=match_parent android:layout_height=wrap_content android:text=删除一条记录 android:textSize=20sp
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