ContentResolver之前在介绍联系人的时候已经用过了,用于查询另一个程序的数据库,相对的,而ContentProvider就是把自己的数据库提供给其他程序查询。 ChatDataProvider:
package com.pocketdigi.provider;
import android.content.ContentProvider;
import android.content.ContentValues;
import android.content.UriMatcher;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.net.Uri;
import com.pocketdigi.db.DatabaseHelper;
public class ChatDataProvider extends ContentProvider {
@Override
public boolean onCreate() {
// TODO Auto-generated method stub
return false;
}
@Override
public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {
// TODO Auto-generated method stub
//查询未读总数
UriMatcher sMatcher = new UriMatcher(UriMatcher.NO_MATCH);
Cursor cursor=null;
//查询未读,匹配URI content://com.pocketdigi.provider/unread
sMatcher.addURI("com.pocketdigi.provider", "unread", 1);
switch(sMatcher.match(uri))
{
case 1:
DatabaseHelper dbHelper=new DatabaseHelper( this.getContext());
SQLiteDatabase db=dbHelper.getWritableDatabase();
cursor= db.rawQuery("select count(*) as count from message where readed=0;",null);
break;
}
return cursor;
}
@Override
public String getType(Uri uri) {
// TODO Auto-generated method stub
return null;
}
@Override
public Uri insert(Uri uri, ContentValues values) {
// TODO Auto-generated method stub
return null;
}
@Override
public int delete(Uri uri, String selection, String[] selectionArgs) {
// TODO Auto-generated method stub
return 0;
}
@Override
public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {
// TODO Auto-generated method stub
return 0;
}
}
功能简单,只能查询未读的消息数量,所以query里很多参数都忽略了,各个参数可以参考db.query的参数列表。 AndroidManifest.xml里注册Provider:
<provider
android:name="com.pocketdigi.provider.ChatDataProvider"
android:authorities="com.pocketdigi.provider" >
</provider>
另一个程序中的使用方法:
ContentResolver resolver=getContentResolver();
Uri uri=Uri.parse("content://com.pocketdigi.provider/unread");
Cursor cursor=resolver.query(uri, null, null, null, null);
if(cursor!=null)
{
cursor.moveToFirst();
int count=cursor.getInt(0);
updateUnReadCountUI(count);
}