工作中遇到了contentprovider数据共享机制,下面来总结一下:
一、ContentProvider简介
当应用继承ContentProvider类,并重写该类用于提供数据和存储数据的方法,就可以向其他应用共享其数据。虽然使用其他方法也可以对外共享数据,但数据访问方式会因数据存储的方式而不同,如:采用文件方式对外共享数据,需要进行文件操作读写数据;采用sharedpreferences共享数据,需要使用sharedpreferences API读写数据。而使用ContentProvider共享数据的好处是统一了数据访问方式。
二、Uri类简介
Uri代表了要操作的数据,Uri主要包含了两部分信息:1.需要操作的ContentProvider ,2.对ContentProvider中的什么数据进行操作,一个Uri由以下几部分组成:
1.scheme:ContentProvider(内容提供者)的scheme已经由Android所规定为:content://。
2.主机名(或Authority):用于唯一标识这个ContentProvider,外部调用者可以根据这个标识来找到它。
3.路径(path):可以用来表示我们要操作的数据,路径的构建应根据业务而定,如下:
• 要操作contact表中id为10的记录,可以构建这样的路径:/contact/10
• 要操作contact表中id为10的记录的name字段, contact/10/name
• 要操作contact表中的所有记录,可以构建这样的路径:/contact
要操作的数据不一定来自数据库,也可以是文件等他存储方式,如下:
要操作xml文件中contact节点下的name节点,可以构建这样的路径:/contact/name
如果要把一个字符串转换成Uri,可以使用Uri类中的parse()方法,如下:
Uri uri = Uri.parse("content://com.changcheng.provider.contactprovider/contact")
三、UriMatcher、ContentUrist和ContentResolver简介
因为Uri代表了要操作的数据,所以我们很经常需要解析Uri,并从Uri中获取数据。Android系统提供了两个用于操作Uri的工具类,分别为UriMatcher 和ContentUris 。掌握它们的使用,会便于我们的开发工作。
UriMatcher:用于匹配Uri,它的用法如下:
1.首先把你需要匹配Uri路径全部给注册上,如下:
//常量UriMatcher.NO_MATCH表示不匹配任何路径的返回码(-1)。
UriMatcher uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
//如果match()方法匹配content://com.changcheng.sqlite.provider.contactprovider/contact路径,返回匹配码为1
uriMatcher.addURI(“com.changcheng.sqlite.provider.contactprovider”, “contact”, 1);//添加需要匹配uri,如果匹配就会返回匹配码
//如果match()方法匹配 content://com.changcheng.sqlite.provider.contactprovider/contact/230路径,返回匹配码为2
uriMatcher.addURI(“com.changcheng.sqlite.provider.contactprovider”, “contact/#”, 2);//#号为通配符
2.注册完需要匹配的Uri后,就可以使用uriMatcher.match(uri)方法对输入的Uri进行匹配,如果匹配就返回匹配码,匹配码是调用addURI()方法传入的第三个参数,假设匹配content://com.changcheng.sqlite.provider.contactprovider/contact路径,返回的匹配码为1。
ContentUris:用于获取Uri路径后面的ID部分,它有两个比较实用的方法:
• withAppendedId(uri, id)用于为路径加上ID部分
• parseId(uri)方法用于从路径中获取ID部分
ContentResolver:当外部应用需要对ContentProvider中的数据进行添加、删除、修改和查询操作时,可以使用ContentResolver 类来完成,要获取ContentResolver 对象,可以使用Activity提供的getContentResolver()方法。 ContentResolver使用insert、delete、update、query方法,来操作数据。
四、ContentProvider示例程序
Manifest.xml中的代码:
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需要在
首先定义一个数据库的工具类:
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public
class
RuiXin {
public
static
final
String DBNAME =
"ruixinonlinedb"
;
public
static
final
String TNAME =
"ruixinonline"
;
public
static
final
int
VERSION =
3
;
public
static
String TID =
"tid"
;
public
static
final
String EMAIL =
"email"
;
public
static
final
String USERNAME =
"username"
;
public
static
final
String DATE =
"date"
;
public
static
final
String SEX =
"sex"
;
public
static
final
String AUTOHORITY =
"com.ruixin.login"
;
public
static
final
int
ITEM =
1
;
public
static
final
int
ITEM_ID =
2
;
public
static
final
String CONTENT_TYPE =
"vnd.android.cursor.dir/vnd.ruixin.login"
;
public
static
final
String CONTENT_ITEM_TYPE =
"vnd.android.cursor.item/vnd.ruixin.login"
;
public
static
final
Uri CONTENT_URI = Uri.parse(
"content://"
+ AUTOHORITY +
"/ruixinonline"
);
}
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public
class
DBlite
extends
SQLiteOpenHelper {
public
DBlite(Context context) {
super
(context, RuiXin.DBNAME,
null
, RuiXin.VERSION);
// TODO Auto-generated constructor stub
}
@Override
public
void
onCreate(SQLiteDatabase db) {
// TODO Auto-generated method stub
db.execSQL(
"create table "
+RuiXin.TNAME+
"("
+
RuiXin.TID+
" integer primary key autoincrement not null,"
+
RuiXin.EMAIL+
" text not null,"
+
RuiXin.USERNAME+
" text not null,"
+
RuiXin.DATE+
" interger not null,"
+
RuiXin.SEX+
" text not null);"
);
}
@Override
public
void
onUpgrade(SQLiteDatabase db,
int
oldVersion,
int
newVersion) {
// TODO Auto-generated method stub
}
public
void
add(String email,String username,String date,String sex){
SQLiteDatabase db = getWritableDatabase();
ContentValues values =
new
ContentValues();
values.put(RuiXin.EMAIL, email);
values.put(RuiXin.USERNAME, username);
values.put(RuiXin.DATE, date);
values.put(RuiXin.SEX, sex);
db.insert(RuiXin.TNAME,
""
,values);
}
}
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public
class
MyProvider
extends
ContentProvider{
DBlite dBlite;
SQLiteDatabase db;
private
static
final
UriMatcher sMatcher;
static
{
sMatcher =
new
UriMatcher(UriMatcher.NO_MATCH);
sMatcher.addURI(RuiXin.AUTOHORITY,RuiXin.TNAME, RuiXin.ITEM);
sMatcher.addURI(RuiXin.AUTOHORITY, RuiXin.TNAME+
"/#"
, RuiXin.ITEM_ID);
}
@Override
public
int
delete(Uri uri, String selection, String[] selectionArgs) {
// TODO Auto-generated method stub
db = dBlite.getWritableDatabase();
int
count =
0
;
switch
(sMatcher.match(uri)) {
case
RuiXin.ITEM:
count = db.delete(RuiXin.TNAME,selection, selectionArgs);
break
;
case
RuiXin.ITEM_ID:
String id = uri.getPathSegments().get(
1
);
count = db.delete(RuiXin.TID, RuiXin.TID+
"="
+id+(!TextUtils.isEmpty(RuiXin.TID=
"?"
)?
"AND("
+selection+
')'
:
""
), selectionArgs);
break
;
default
:
throw
new
IllegalArgumentException(
"Unknown URI"
+uri);
}
getContext().getContentResolver().notifyChange(uri,
null
);
return
count;
}
@Override
public
String getType(Uri uri) {
// TODO Auto-generated method stub
switch
(sMatcher.match(uri)) {
case
RuiXin.ITEM:
return
RuiXin.CONTENT_TYPE;
case
RuiXin.ITEM_ID:
return
RuiXin.CONTENT_ITEM_TYPE;
default
:
throw
new
IllegalArgumentException(
"Unknown URI"
+uri);
}
}
@Override
public
Uri insert(Uri uri, ContentValues values) {
// TODO Auto-generated method stub
db = dBlite.getWritableDatabase();
long
rowId;
if
(sMatcher.match(uri)!=RuiXin.ITEM){
throw
new
IllegalArgumentException(
"Unknown URI"
+uri);
}
rowId = db.insert(RuiXin.TNAME,RuiXin.TID,values);
if
(rowId>
0
){
Uri noteUri=ContentUris.withAppendedId(RuiXin.CONTENT_URI, rowId);
getContext().getContentResolver().notifyChange(noteUri,
null
);
return
noteUri;
}
throw
new
IllegalArgumentException(
"Unknown URI"
+uri);
}
@Override
public
boolean
onCreate() {
// TODO Auto-generated method stub
this
.dBlite =
new
DBlite(
this
.getContext());
// db = dBlite.getWritableDatabase();
// return (db == null)?false:true;
return
true
;
}
@Override
public
Cursor query(Uri uri, String[] projection, String selection,
String[] selectionArgs, String sortOrder) {
// TODO Auto-generated method stub
db = dBlite.getWritableDatabase();
Cursor c;
Log.d(
"-------"
, String.valueOf(sMatcher.match(uri)));
switch
(sMatcher.match(uri)) {
case
RuiXin.ITEM:
c = db.query(RuiXin.TNAME, projection, selection, selectionArgs,
null
,
null
,
null
);
break
;
case
RuiXin.ITEM_ID:
String id = uri.getPathSegments().get(
1
);
c = db.query(RuiXin.TNAME, projection, RuiXin.TID+
"="
+id+(!TextUtils.isEmpty(selection)?
"AND("
+selection+
')'
:
""
),selectionArgs,
null
,
null
, sortOrder);
break
;
default
:
Log.d(
"!!!!!!"
,
"Unknown URI"
+uri);
throw
new
IllegalArgumentException(
"Unknown URI"
+uri);
}
c.setNotificationUri(getContext().getContentResolver(), uri);
return
c;
}
@Override
public
int
update(Uri uri, ContentValues values, String selection,
String[] selectionArgs) {
// TODO Auto-generated method stub
return
0
;
}
}
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public
class
TestWebviewDemo
extends
Activity {
/** Called when the activity is first created. */
private
DBlite dBlite1 =
new
DBlite(
this
);;
private
ContentResolver contentResolver;
public
void
onCreate(Bundle savedInstanceState) {
super
.onCreate(savedInstanceState);
setContentView(R.layout.main);
//先对数据库进行添加数据
dBlite1.add("[email protected]", "a", "2012.9.17", "男");
//通过contentResolver进行查找
contentResolver = TestWebviewDemo.
this
.getContentResolver();
Cursor cursor = contentResolver.query(
RuiXin.CONTENT_URI,
new
String[] {
RuiXin.EMAIL, RuiXin.USERNAME,
RuiXin.DATE,RuiXin.SEX },
null
,
null
,
null
);
while
(cursor.moveToNext()) {
Toast.makeText(
TestWebviewDemo.
this
,
cursor.getString(cursor.getColumnIndex(RuiXin.EMAIL))
+
" "
+ cursor.getString(cursor.getColumnIndex(RuiXin.USERNAME))
+
" "
+ cursor.getString(cursor.getColumnIndex(RuiXin.DATE))
+
" "
+ cursor.getString(cursor.getColumnIndex(RuiXin.SEX)),
Toast.LENGTH_SHORT).show();
}
startManagingCursor(cursor);
//查找后关闭游标
}
}
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public
class
Test
extends
Activity {
/** Called when the activity is first created. */
private
ContentResolver contentResolver;
public
void
onCreate(Bundle savedInstanceState) {
super
.onCreate(savedInstanceState);
setContentView(R.layout.main);
//通过contentResolver进行查找
contentResolver = TestWebviewDemo.
this
.getContentResolver();
Cursor cursor = contentResolver.query(
RuiXin.CONTENT_URI,
new
String[] {
RuiXin.EMAIL, RuiXin.USERNAME,
RuiXin.DATE,RuiXin.SEX },
null
,
null
,
null
);
while
(cursor.moveToNext()) {
Toast.makeText(TestWebviewDemo.
this
,
cursor.getString(cursor.getColumnIndex(RuiXin.EMAIL))
+
" "
+ cursor.getString(cursor.getColumnIndex(RuiXin.USERNAME))
+
" "
+ cursor.getString(cursor.getColumnIndex(RuiXin.DATE))
+
" "
+ cursor.getString(cursor.getColumnIndex(RuiXin.SEX)),
Toast.LENGTH_SHORT).show();
}
startManagingCursor(cursor);
//查找后关闭游标
}
}
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