Android中ContentProvider和ContentResolver详解

2024-02-25 07:21:05 51

Android中ContentProvider和ContentResolver详解

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）AIDL2）Broadcast3）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：

packagecom.backgroundservice;

importandroid.content.ContentProvider;
importandroid.content.ContentValues;
importandroid.content.UriMatcher;
importandroid.database.Cursor;
importandroid.database.sqlite.SQLiteDatabase;
importandroid.database.sqlite.SQLiteQueryBuilder;
importandroid.NET.Uri;
importandroid.util.Log;

/**
*TODO
*
*@authorzengpeng
*@version1.0CreateAt:2010-3-18下午02:52:40
*/
publicclassTestContentProviderextendsContentProvider{
privateSQLiteDatabasemDb;
privateDatabaseHelpermDbHelper=null;
privatestaticfinalStringDATABASE_NAME="rssitems.db";
privatestaticfinalStringDATABASE_TABLE_NAME="rssItems";
privatestaticfinalintDB_VERSION=1;
privatestaticfinalintALL_MESSAGES=1;
privatestaticfinalintSPECIFIC_MESSAGE=2;

//SetupourURLmatcherstohelpusdeterminewhatan
//incomingURIparameteris.
privatestaticfinalUriMatcherURI_MATCHER;
static{
URI_MATCHER=newUriMatcher(UriMatcher.NO_MATCH);
URI_MATCHER.addURI("test","item",ALL_MESSAGES);
URI_MATCHER.addURI("test","item/#",SPECIFIC_MESSAGE);
}

//Here'sthepublicURIusedtoqueryforRSSitems.
publicstaticfinalUriCONTENT_URI=Uri
.parse("content://test/item");

//Hereareourcolumnnameconstants,usedtoqueryforfieldvalues.

publicstaticfinalStringID="_id";
publicstaticfinalStringNAME="NAME";
publicstaticfinalStringVALUE="VALUE";
publicstaticfinalStringDEFAULT_SORT_ORDER=ID+"DESC";

privatestaticclassDatabaseHelperextendsAbstractDatabaseHelper{

@Override
protectedString[]createDBTables(){
//TODOAuto-generatedmethodstub
Stringsql="CREATETABLE"+DATABASE_TABLE_NAME+"("+ID
+"INTEGERPRIMARYKEYAUTOINCREMENT,"+NAME+"TEXT,"
+VALUE+"TEXT);";
returnnewString[]{sql};
}

@Override
protectedString[]dropDBTables(){
//TODOAuto-generatedmethodstub
returnnull;
}

@Override
protectedStringgetDatabaseName(){
//TODOAuto-generatedmethodstub
returnDATABASE_NAME;
}

@Override
protectedintgetDatabaseVersion(){
//TODOAuto-generatedmethodstub
returnDB_VERSION;
}

@Override
protectedStringgetTag(){
//TODOAuto-generatedmethodstub
returnTestContentProvider.class.getSimpleName();}

}

/**
*
*/
publicTestContentProvider(){
//TODOAuto-generatedconstructorstub

}

/*
*(non-Javadoc)
*
*@seeandroid.content.ContentProvider#delete(android.Net.Uri,
*Java.lang.String,java.lang.String[])
*/
@Override
publicintdelete(Uriuri,Stringselection,String[]selectionArgs){
//NOTEArgumentcheckingcodeomitted.Checkyourparameters!
introwCount=mDb.delete(DATABASE_TABLE_NAME,selection,selectionArgs);

//Notifyanylistenersandreturnthedeletedrowcount.
getContext().getContentResolver().notifyChange(uri,null);
returnrowCount;
}

/*
*(non-Javadoc)
*
*@seeandroid.content.ContentProvider#getType(android.net.Uri)
*/
@Override
publicStringgetType(Uriuri){
switch(URI_MATCHER.match(uri)){
caseALL_MESSAGES:
return"vnd.android.cursor.dir/rssitem";//Listofitems.
caseSPECIFIC_MESSAGE:
return"vnd.android.cursor.item/rssitem";//Specificitem.
default:
returnnull;
}
}

/*
*(non-Javadoc)
*
*@seeandroid.content.ContentProvider#insert(android.net.Uri,
*android.content.ContentValues)
*/
@Override
publicUriinsert(Uriuri,ContentValuesvalues){
//NOTEArgumentcheckingcodeomitted.Checkyourparameters!Checkthat
//yourrowadditionrequestsucceeded!
longrowId=-1;
rowId=mDb.insert(DATABASE_TABLE_NAME,NAME,values);
UrinewUri=Uri.withAppendedPath(CONTENT_URI,""+rowId);
Log.i("TestContentProvider","savedarecord"+rowId+""+newUri);
//NotifyanylistenersandreturntheURIofthenewrow.
getContext().getContentResolver().notifyChange(CONTENT_URI,null);
returnnewUri;
}

/*
*(non-Javadoc)
*
*@seeandroid.content.ContentProvider#onCreate()
*/
@Override
publicbooleanonCreate(){
//TODOAuto-generatedmethodstub
try
{
mDbHelper=newDatabaseHelper();
mDbHelper.open(getContext());
mDb=mDbHelper.getMDb();
}catch(Exceptione){
e.printStackTrace();
}
returntrue;
}

/*
*(non-Javadoc)
*
*@seeandroid.content.ContentProvider#query(android.net.Uri,
*java.lang.String[],java.lang.String,java.lang.String[],
*java.lang.String)
*/
publicCursorquery(Uriuri,String[]projection,Stringselection,
String[]selectionArgs,StringsortOrder){
//Wewon'tbothercheckingthevalidityofparamshere,butyoushould!

//SQLiteQueryBuilderisthehelperclassthatcreatesthe
//properSQLsyntaxforus.
SQLiteQueryBuilderqBuilder=newSQLiteQueryBuilder();

//Setthetablewe'requerying.
qBuilder.setTables(DATABASE_TABLE_NAME);

//Ifthequeryendsinaspecificrecordnumber,we're
//beingaskedforaspecificrecord,sosetthe

//WHEREclauseinourquery.
if((URI_MATCHER.match(uri))==SPECIFIC_MESSAGE){
qBuilder.appendWhere("_id="+uri.getLastPathSegment());
Log.i("TestContentProvider","_id="+uri.getLastPathSegment());
}


//Makethequery.
Cursorc=qBuilder.query(mDb,
projection,
selection,
selectionArgs,
null,
null,
sortOrder);
Log.i("TestContentProvider","getrecords");
c.setNotificationUri(getContext().getContentResolver(),uri);
returnc;
}

/*
*(non-Javadoc)
*
*@seeandroid.content.ContentProvider#update(android.net.Uri,
*android.content.ContentValues,java.lang.String,java.lang.String[])
*/
@Override
publicintupdate(Uriuri,ContentValuesvalues,Stringselection,
String[]selectionArgs){
//NOTEArgumentcheckingcodeomitted.Checkyourparameters!
intupdateCount=mDb.update(DATABASE_TABLE_NAME,values,selection,selectionArgs);

//Notifyanylistenersandreturntheupdatedrowcount.
getContext().getContentResolver().notifyChange(uri,null);
returnupdateCount;
}

}

配文件如下：

在客户端中可以使用如下方法进行调用：

ContentValuesvalues=newContentValues();
values.put(TestContentProvider.NAME,"testname1");
values.put(TestContentProvider.VALUE,"testvalu1e");
UrinewAddUri=TestActivity.this.getContentResolver().insert(TestContentProvider.CONTENT_URI,values);
Cursorc=TestActivity.this.managedQuery(newAddUri,newString[]{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。

感谢阅读，希望能帮助到大家，谢谢大家对本站的支持！

Android中ContentProvider和ContentResolver详解

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