Android 中自定义ContentProvider与ContentObserver的使用简单实例

2023-09-25 08:08:05 214

Android中自定义ContentProvider与ContentObserver的使用简单实例

示例说明:

该示例中一共包含两个工程。其中一个工程完成了自定义ContentProvider，另外一个工程用于测试该自定义ContentProvider且在该工程中使用了ContentObserver监听自定义ContentProvider的数据变化

以下代码为工程TestContentProvider

ContentProviderTest如下:

packagecn.testcontentprovider;
importandroid.content.ContentProvider;
importandroid.content.ContentUris;
importandroid.content.ContentValues;
importandroid.content.UriMatcher;
importandroid.database.Cursor;
importandroid.database.sqlite.SQLiteDatabase;
importandroid.net.Uri;
/**
*Demo描述:
*自定义ContentProvider的实现
*ContentProvider主要用于在不同的应用程序之间共享数据,这也是官方推荐的方式.
*
*注意事项:
*1在AndroidManifest.xml中注册ContentProvider时的属性
*android:exported="true"表示允许其他应用访问.
*2注意*和#这两个符号在Uri中的作用
*其中*表示匹配任意长度的字符
*其中#表示匹配任意长度的数据
*所以：
*一个能匹配所有表的Uri可以写成:
*content://cn.bs.testcontentprovider/*
*一个能匹配person表中任意一行的Uri可以写成:
*content://cn.bs.testcontentprovider/person/#
*
*/
publicclassContentProviderTestextendsContentProvider{
privateSQLiteDatabaseOpenHelpermSQLiteDatabaseOpenHelper;
privatefinalstaticStringAUTHORITY="cn.bs.testcontentprovider";
privatestaticUriMatchermUriMatcher;
privatestaticfinalintPERSON_DIR=0;
privatestaticfinalintPERSON=1;

/**
*利用静态代码块初始化UriMatcher
*在UriMatcher中包含了多个Uri,每个Uri代表一种操作
*当调用UriMatcher.match(Uriuri)方法时就会返回该uri对应的code;
*比如此处的PERSONS和PERSON
*/
static{
mUriMatcher=newUriMatcher(UriMatcher.NO_MATCH);
//该URI表示返回所有的person,其中PERSONS为该特定Uri的标识码
mUriMatcher.addURI(AUTHORITY,"person",PERSON_DIR);
//该URI表示返回某一个person,其中PERSON为该特定Uri的标识码
mUriMatcher.addURI(AUTHORITY,"person/#",PERSON);
}


/**
*在自定义ContentProvider中必须覆写getType(Uriuri)方法.
*该方法用于获取Uri对象所对应的MIME类型.
*
*一个Uri对应的MIME字符串遵守以下三点:
*1必须以vnd开头
*2如果该Uri对应的数据可能包含多条记录,那么返回字符串应该以"vnd.android.cursor.dir/"开头
*3如果该Uri对应的数据只包含一条记录,那么返回字符串应该以"vnd.android.cursor.item/"开头
*/
@Override
publicStringgetType(Uriuri){
switch(mUriMatcher.match(uri)){
casePERSON_DIR:
return"vnd.android.cursor.dir/"+AUTHORITY+".persons";
casePERSON:
return"vnd.android.cursor.item/"+AUTHORITY+".person";
default:
thrownewIllegalArgumentException("unknownuri"+uri.toString());
}
}


@Override
publicbooleanonCreate(){
mSQLiteDatabaseOpenHelper=newSQLiteDatabaseOpenHelper(getContext());
returntrue;
}


/**
*插入操作:
*插入操作只有一种可能:向一张表中插入
*返回结果为新增记录对应的Uri
*方法db.insert()返回结果为新增记录对应的主键值
*/
@Override
publicUriinsert(Uriuri,ContentValuesvalues){
SQLiteDatabasedb=mSQLiteDatabaseOpenHelper.getWritableDatabase();
switch(mUriMatcher.match(uri)){
casePERSON_DIR:
longnewId=db.insert("person","name,phone,salary",values);
//向外界通知该ContentProvider里的数据发生了变化,以便ContentObserver作出相应
getContext().getContentResolver().notifyChange(uri,null);
returnContentUris.withAppendedId(uri,newId);
default:
thrownewIllegalArgumentException("unknownuri"+uri.toString());
}
}

/**
*更新操作:
*更新操作有两种可能:更新一张表或者更新某条数据
*在更新某条数据时原理类似于查询某条数据,见下.
*/
@Override
publicintupdate(Uriuri,ContentValuesvalues,Stringselection,String[]selectionArgs){
SQLiteDatabasedb=mSQLiteDatabaseOpenHelper.getWritableDatabase();
intupdatedNum=0;
switch(mUriMatcher.match(uri)){
//更新表
casePERSON_DIR:
updatedNum=db.update("person",values,selection,selectionArgs);
break;
//按照id更新某条数据
casePERSON:
longid=ContentUris.parseId(uri);
Stringwhere="personid="+id;
if(selection!=null&&!"".equals(selection.trim())){
where=selection+"and"+where;
}
updatedNum=db.update("person",values,where,selectionArgs);
break;
default:
thrownewIllegalArgumentException("unknownuri"+uri.toString());
}
//向外界通知该ContentProvider里的数据发生了变化,以便ContentObserver作出相应
getContext().getContentResolver().notifyChange(uri,null);
returnupdatedNum;
}

/**
*删除操作:
*删除操作有两种可能:删除一张表或者删除某条数据
*在删除某条数据时原理类似于查询某条数据,见下.
*/
@Override
publicintdelete(Uriuri,Stringselection,String[]selectionArgs){
SQLiteDatabasedb=mSQLiteDatabaseOpenHelper.getWritableDatabase();
intdeletedNum=0;
switch(mUriMatcher.match(uri)){
//删除表
casePERSON_DIR:
deletedNum=db.delete("person",selection,selectionArgs);
break;
//按照id删除某条数据
casePERSON:
longid=ContentUris.parseId(uri);
Stringwhere="personid="+id;
if(selection!=null&&!"".equals(selection.trim())){
where=selection+"and"+where;
}
deletedNum=db.delete("person",where,selectionArgs);
break;
default:
thrownewIllegalArgumentException("unknownuri"+uri.toString());
}
//向外界通知该ContentProvider里的数据发生了变化,以便ContentObserver作出相应
getContext().getContentResolver().notifyChange(uri,null);
returndeletedNum;
}

/**
*查询操作:
*查询操作有两种可能:查询一张表或者查询某条数据
*
*注意事项:
*在查询某条数据时要注意--因为此处是按照personid来查询
*某条数据,但是同时可能还有其他限制.例如:
*要求personid为2且name为xiaoming1
*所以在查询时分为两步:
*第一步:
*解析出personid放入where查询条件
*第二步:
*判断是否有其他限制(如name),若有则将其组拼到where查询条件.
*
*详细代码见下.
*/
@Override
publicCursorquery(Uriuri,String[]projection,Stringselection,String[]selectionArgs,StringsortOrder){
SQLiteDatabasedb=mSQLiteDatabaseOpenHelper.getWritableDatabase();
Cursorcursor=null;
switch(mUriMatcher.match(uri)){
//查询表
casePERSON_DIR:
cursor=db.query("person",projection,selection,selectionArgs,null,null,sortOrder);
break;
//按照id查询某条数据
casePERSON:
//第一步:
longid=ContentUris.parseId(uri);
Stringwhere="personid="+id;
//第二步:
if(selection!=null&&!"".equals(selection.trim())){
where=selection+"and"+where;
}
cursor=db.query("person",projection,where,selectionArgs,null,null,sortOrder);
break;
default:
thrownewIllegalArgumentException("unknownuri"+uri.toString());
}
returncursor;
}


}

SQLiteDatabaseOpenHelper如下:

packagecn.testcontentprovider;
importandroid.content.Context;
importandroid.database.sqlite.SQLiteDatabase;
importandroid.database.sqlite.SQLiteOpenHelper;
publicclassSQLiteDatabaseOpenHelperextendsSQLiteOpenHelper{
publicSQLiteDatabaseOpenHelper(Contextcontext){
super(context,"contentprovidertest.db",null,1);
}

@Override
publicvoidonCreate(SQLiteDatabasedb){
db.execSQL("createtableperson(personidintegerprimarykeyautoincrement,namevarchar(20),phonevarchar(12),salaryInteger(12))");
}

//当数据库版本号发生变化时调用该方法
@Override
publicvoidonUpgrade(SQLiteDatabasedb,intarg1,intarg2){
//db.execSQL("ALTERTABLEpersonADDphonevarchar(12)NULL");
//db.execSQL("ALTERTABLEpersonADDsalaryIntegerNULL");
}

}

MainActivity如下:
[java]viewplaincopy
packagecn.testcontentprovider;
importandroid.app.Activity;
importandroid.os.Bundle;
publicclassMainActivityextendsActivity{
@Override
protectedvoidonCreate(BundlesavedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
}

}

AndroidManifest.xml如下:

main.xml如下:

以下代码为工程TestBaidu

MainActivity如下:

packagecn.testbaidu;
importandroid.net.Uri;
importandroid.os.Bundle;
importandroid.os.Handler;
importandroid.view.View;
importandroid.view.View.OnClickListener;
importandroid.widget.Button;
importandroid.app.Activity;
importandroid.content.ContentResolver;
importandroid.content.ContentValues;
importandroid.database.ContentObserver;
importandroid.database.Cursor;
/**
*Demo描述:
*应用A(TestBaidu)调用另外一个应用(TestContentProvider)中的自定义ContentProvider,即:
*1自定义ContentProvider的使用
*2其它应用调用该ContentProvider
*3ContentObserver的使用
*
*备注说明:
*1该例子在以前版本的基础上整理了代码
*2该例子在以前版本的基础上融合了ContentObserver的使用
*利用ContentObserver随时监听ContentProvider的数据变化.
*为实现该功能需要在自定义的ContentProvider的insert(),update(),delete()
*方法中调用getContext().getContentResolver().notifyChange(uri,null);
*向外界通知该ContentProvider里的数据发生了变化,以便ContentObserver作出相应
*
*测试方法:
*1依次测试ContentProvider的增查删改(注意该顺序)!!
*2其它应用查询该ContentProvider的数据
*
*/
publicclassMainActivityextendsActivity{
privateButtonmAddButton;
privateButtonmDeleteButton;
privateButtonmUpdateButton;
privateButtonmQueryButton;
privateButtonmTypeButton;
privatelonglastTime=0;
privateContentResolvermContentResolver;
privateContentObserverSubClassmContentObserverSubClass;
@Override
protectedvoidonCreate(BundlesavedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
init();
initContentObserver();
}

privatevoidinit(){
mContentResolver=this.getContentResolver();

mAddButton=(Button)findViewById(R.id.addButton);
mAddButton.setOnClickListener(newClickListenerImpl());

mDeleteButton=(Button)findViewById(R.id.deleteButton);
mDeleteButton.setOnClickListener(newClickListenerImpl());

mUpdateButton=(Button)findViewById(R.id.updateButton);
mUpdateButton.setOnClickListener(newClickListenerImpl());

mQueryButton=(Button)findViewById(R.id.queryButton);
mQueryButton.setOnClickListener(newClickListenerImpl());

mTypeButton=(Button)findViewById(R.id.typeButton);
mTypeButton.setOnClickListener(newClickListenerImpl());

}



//注册一个针对ContentProvider的ContentObserver用来观察内容提供者的数据变化
privatevoidinitContentObserver(){
Uriuri=Uri.parse("content://cn.bs.testcontentprovider/person");
mContentObserverSubClass=newContentObserverSubClass(newHandler());
this.getContentResolver().registerContentObserver(uri,true,mContentObserverSubClass);
}

@Override
protectedvoidonDestroy(){
super.onDestroy();
if(mContentObserverSubClass!=null){
this.getContentResolver().unregisterContentObserver(mContentObserverSubClass);
}
}




//自定义一个内容观察者ContentObserver
privateclassContentObserverSubClassextendsContentObserver{

publicContentObserverSubClass(Handlerhandler){
super(handler);
}

//采用时间戳避免多次调用onChange()
@Override
publicvoidonChange(booleanselfChange){
super.onChange(selfChange);
System.out.println("ContentObserveronChange()selfChange="+selfChange);
if(System.currentTimeMillis()-lastTime>2000){
ContentResolverresolver=getContentResolver();
Uriuri=Uri.parse("content://cn.bs.testcontentprovider/person");
//获取最新的一条数据
Cursorcursor=resolver.query(uri,null,null,null,"personiddesclimit1");
while(cursor.moveToNext()){
intpersonid=cursor.getInt(cursor.getColumnIndex("personid"));
System.out.println("内容提供者中的数据发生变化,现数据中第一条数据的personid="+personid);
}
cursor.close();
lastTime=System.currentTimeMillis();
}else{
System.out.println("时间间隔过短,忽略此次更新");
}


}

@Override
publicbooleandeliverSelfNotifications(){
returntrue;
}

}





privateclassClickListenerImplimplementsOnClickListener{
@Override
publicvoidonClick(Viewv){
switch(v.getId()){
caseR.id.addButton:
Personperson=null;
for(inti=0;i<5;i++){
person=newPerson("xiaoming"+i,"9527"+i,(8888+i));
testInsert(person);
}
break;
caseR.id.deleteButton:
testDelete(1);
break;
caseR.id.updateButton:
testUpdate(3);
break;
caseR.id.queryButton:
//查询表
//queryFromContentProvider(-1);

//查询personid=2的数据
testQuery(2);
break;
caseR.id.typeButton:
testType();
break;
default:
break;
}

}

}
privatevoidtestInsert(Personperson){
ContentValuescontentValues=newContentValues();
contentValues.put("name",person.getName());
contentValues.put("phone",person.getPhone());
contentValues.put("salary",person.getSalary());
UriinsertUri=Uri.parse("content://cn.bs.testcontentprovider/person");
UrireturnUri=mContentResolver.insert(insertUri,contentValues);
System.out.println("新增数据:returnUri="+returnUri);
}

privatevoidtestDelete(intindex){
Uriuri=Uri.parse("content://cn.bs.testcontentprovider/person/"+String.valueOf(index));
mContentResolver.delete(uri,null,null);
}

privatevoidtestUpdate(intindex){
Uriuri=Uri.parse("content://cn.bs.testcontentprovider/person/"+String.valueOf(index));
ContentValuesvalues=newContentValues();
values.put("name","hanmeimei");
values.put("phone","1234");
values.put("salary",333);
mContentResolver.update(uri,values,null,null);
}

privatevoidtestQuery(intindex){
Uriuri=null;
if(index<=0){
//查询表
uri=Uri.parse("content://cn.bs.testcontentprovider/person");
}else{
//按照id查询某条数据
uri=Uri.parse("content://cn.bs.testcontentprovider/person/"+String.valueOf(index));
}

//对应上面的:查询表
//Cursorcursor=mContentResolver.query(uri,null,null,null,null);

//对应上面的:查询personid=2的数据
//注意:因为name是varchar字段的,所以应该写作"name='xiaoming1'"
//若写成"name=xiaoming1"查询时会报错
Cursorcursor=mContentResolver.query(uri,null,"name='xiaoming1'",null,null);

while(cursor.moveToNext()){
intpersonid=cursor.getInt(cursor.getColumnIndex("personid"));
Stringname=cursor.getString(cursor.getColumnIndex("name"));
Stringphone=cursor.getString(cursor.getColumnIndex("phone"));
intsalary=cursor.getInt(cursor.getColumnIndex("salary"));
System.out.println("查询得到:personid="+personid+",name="+name+",phone="+phone+",salary="+salary);
}
cursor.close();
}

privatevoidtestType(){
UridirUri=Uri.parse("content://cn.bs.testcontentprovider/person");
StringdirType=mContentResolver.getType(dirUri);
System.out.println("dirType:"+dirType);

UriitemUri=Uri.parse("content://cn.bs.testcontentprovider/person/3");
StringitemType=mContentResolver.getType(itemUri);
System.out.println("itemType:"+itemType);
}

}

Person如下:

packagecn.testbaidu;

publicclassPerson{
privateIntegerid;
privateStringname;
privateStringphone;
privateIntegersalary;
publicPerson(Stringname,Stringphone,Integersalary){
this.name=name;
this.phone=phone;
this.salary=salary;
}
publicPerson(Integerid,Stringname,Stringphone,Integersalary){
this.id=id;
this.name=name;
this.phone=phone;
this.salary=salary;
}
publicIntegergetId(){
returnid;
}
publicvoidsetId(Integerid){
this.id=id;
}
publicStringgetName(){
returnname;
}
publicvoidsetName(Stringname){
this.name=name;
}
publicStringgetPhone(){
returnphone;
}
publicvoidsetPhone(Stringphone){
this.phone=phone;
}
publicIntegergetSalary(){
returnsalary;
}
publicvoidsetSalary(Integersalary){
this.salary=salary;
}
@Override
publicStringtoString(){
return"Person[id="+id+",name="+name+",phone="+phone+",salary="+salary+"]";
}



}

main.xml如下:

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Android 中自定义ContentProvider与ContentObserver的使用简单实例

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