Android之ContentProvider

Android程序的主要4部分：

1、Activiyt

2、BroadcastIntentReceiver

3、Service

4、ContentProvider

一个ContentProvider类实现了一组标准的方法接口，从而能够让其他的应用保存或读取此ContentProvider的各种数据类型。

下面列举一些常用的接口：

1、query(Uriuri,String[]projection,Stringselection,String[]selectionArgs,StringsortOrder):通过Uri进行查询，返回一个Cursor.

2、insert(Uriuri,ContentValuesvalues):将一组数据插入到Uri指定的地方。

3、update(Uriuri,ContentValuesvalues,Stringwhere,String[]selectionArgs):更新Uri指定位置的数据。

4、delete（Uriuri,Stringwhere,String[]selectionArgs）:删除指定Uri并且符合一定条件的数据。

ContentResolver

外界程序通过ContentResolver接口可以访问ContentProvider提供的数据，在Activity当中通过getContentResolver（）可以得到当前应用ContentResolver实例。其提供的接口与ContentProvider提供的接口对应：

1、query(Uriuri,String[]projection,Stringselection,String[]selectionArgs,StringsortOrder):通过Uri进行查询，返回一个Cursor.

2、insert(Uriuri,ContentValuesvalues):将一组数据插入到Uri指定的地方。

3、update(Uriuri,ContentValuesvalues,Stringwhere,String[]selectionArgs):更新Uri指定位置的数据。

4、delete（Uriuri,Stringwhere,String[]selectionArgs）:删除指定Uri并且符合一定条件的数据。

实例：

1.要为当前应用程序的私有数据定义URI，就需要专门定义个继承自ContentProvider的类，然后实现各个不同的操作所调用的方法。

1、PersonProvider

packagecn.class3g.db; importcn.class3g.service.DatabaseHelper; importandroid.content.ContentProvider; importandroid.content.ContentUris; importandroid.content.ContentValues; importandroid.content.UriMatcher; importandroid.database.Cursor; importandroid.database.sqlite.SQLiteDatabase; importandroid.net.Uri; publicclassPersonProviderextendsContentProvider{ privatestaticUriMatchermatcher=newUriMatcher(UriMatcher.NO_MATCH); privatestaticfinalintPERSONS=1; privatestaticfinalintPERSON=2; privateDatabaseHelperdbHelper; static{ matcher.addURI("cn.class3g.providers.personprovider","person",PERSONS); matcher.addURI("cn.class3g.providers.personprovider","person/#", PERSON); } publicbooleanonCreate(){ dbHelper=newDatabaseHelper(this.getContext()); returntrue; } //content://cn.itcast.provides.personprovider/person publicUriinsert(Uriuri,ContentValuesvalues){ SQLiteDatabasedb=dbHelper.getWritableDatabase(); longrowId; switch(matcher.match(uri)){ casePERSONS://向表中添加新纪录并返回其行号 rowId=db.insert("person","personid",values); returnContentUris.withAppendedId(uri,rowId); default: thrownewIllegalArgumentException("UnknowUri:"+uri); } } publicCursorquery(Uriuri,String[]projection,Stringselection, String[]selectionArgs,StringsortOrder){ SQLiteDatabasedb=dbHelper.getReadableDatabase(); switch(matcher.match(uri)){ casePERSONS: returndb.query("person",projection,selection,selectionArgs,null,null,sortOrder); casePERSON: longpersonid=ContentUris.parseId(uri); Stringwhere="personid="+personid; if(selection!=null&&!"".equals(selection)){ where=where+"and"+selection; } returndb.query("person",projection,where,selectionArgs,null,null,sortOrder); default: thrownewIllegalArgumentException("UnknownUri:"+uri); } } //content://cn.itcast.provides.personprovider/person更新表中的所有记录 //content://cn.itcast.provides.personprovider/person/10更新表中指定id的记录 publicintupdate(Uriuri,ContentValuesvalues,Stringselection, String[]selectionArgs){ SQLiteDatabasedb=dbHelper.getWritableDatabase(); intnum; switch(matcher.match(uri)){ casePERSONS://更新指定记录 num=db.update("person",values,selection,selectionArgs); break; casePERSON: longpersonid=ContentUris.parseId(uri); Stringwhere="personid="+personid; if(selection!=null){ where+="and"+selection; } num=db.update("person",values,where,selectionArgs); break; default: thrownewIllegalArgumentException("UnknowUri"+uri); } returnnum; } publicintdelete(Uriuri,Stringselection,String[]selectionArgs){ SQLiteDatabasedb=dbHelper.getWritableDatabase(); intnum=0; switch(matcher.match(uri)){ casePERSONS: num=db.delete("person",selection,selectionArgs); break; casePERSON: longpersonid=ContentUris.parseId(uri); Stringwhere="personid="+personid; if(selection!=null&&!"".equals(selection)){ where=where+"and"+selection; } num=db.delete("person",where,selectionArgs); break; default: thrownewIllegalArgumentException("UnknownUri:"+uri); } returnnum; } publicStringgetType(Uriuri){ switch(matcher.match(uri)){ casePERSONS: return"vnd.android.cursor.dir/person"; casePERSON: return"vnd.android.cursor.item/person"; default: thrownewIllegalArgumentException("UnknownUri:"+uri); } } }

2.在AndroidManifest中配置

<provider

android:authorities="cn.class3g.providers.personprovider"

android:name="PersonProvider">

</provider>

3.建立测试工程编写测试代码

publicclassAccessContentProviderTestextendsAndroidTestCase{

publicvoidtestSave()throwsThrowable{

ContentResolverresolver=this.getContext().getContentResolver();

UriinsertUri=Uri.parse("content://cn.class3g.providers.personprovider/person");

ContentValuesvalues=newContentValues();

values.put("name","laozhang");

values.put("age","50");

Uriuri=resolver.insert(insertUri,values);

Log.i("TAG",uri.toString());

}

publicvoidtestQuery()throwsThrowable{

ContentResolverresolver=this.getContext().getContentResolver();

Uriuri=Uri.parse("content://cn.class3g.providers.personprovider/person");

Cursorcursor=resolver.query(uri,null,null,null,"personidasc");

while(cursor.moveToNext()){

intpersonid=cursor.getInt(cursor.getColumnIndex("personid"));

Stringname=cursor.getString(cursor.getColumnIndex("name"));

Log.i("TAG","personid="+personid+",name="+name);

}

cursor.close();

}

publicvoidtestUpdate()throwsThrowable{

ContentResolvercontentResolver=

this.getContext().getContentResolver();

UriupdateUri=Uri.parse("content://cn.class3g.providers.personprovider/person/5");

ContentValuesvalues=newContentValues();

values.put("name","孙悟空");

contentResolver.update(updateUri,values,null,null);

}

publicvoidtestDelete()throwsThrowable{

ContentResolvercontentResolver=this.getContext().getContentResolver();

Uriuri=Uri.parse("content://cn.class3g.providers.personprovider/person/5");

contentResolver.delete(uri,null,null);

}

}