Android自助餐之内容提供者ContentProvider使用

Android自助餐之内容提供者ContentProvider使用

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创建提供者Module

此例中Module为SampleOfContentProvider

1. 创建Provider类
   此例中类名InfoProvider
2. 在Manifest中声明
   
<provider
android:exported="true"
android:authorities="com.xmh.sampleofcontentprovider"
android:name="com.xmh.sampleofcontentprovider.InfoProvider">
</provider>

3. 明确URI
   定义静态字符串URI_PROVIDER="com.xmh.sampleofcontentprovider"作为访问URI。
4. 在静态代码块中初始化Uri匹配器
   
matcher= new UriMatcher(UriMatcher.NO_MATCH);
matcher.addURI(URI_PROVIDER,"insert",INSERT);
matcher.addURI(URI_PROVIDER,"delete",DELETE);
matcher.addURI(URI_PROVIDER,"update",UPDATE);
matcher.addURI(URI_PROVIDER,"query",QUERY);
matcher.addURI(URI_PROVIDER,"query/#",QUERY_ONE);

5. 在onCreate时初始化数据库操作对象
   
database= getContext().openOrCreateDatabase(SQL_NAME, Context.MODE_PRIVATE, null);
database.execSQL("create table if not exists "+TABLE_NAME+"(id varchar(10),name varchar(10),age int)");
database.execSQL("INSERT INTO "+TABLE_NAME+" VALUES ('001','aa', 10)");
database.execSQL("INSERT INTO "+TABLE_NAME+" VALUES ('002','bb', 20)");
//此处临时创建一个数据库

6. 重写query方法
   
//匹配URI
if(matcher.match(uri)==QUERY){
//执行查询语句并返回游标
Cursor cursor = database.query(TABLE_NAME, projection, selection, selectionArgs, null, null, sortOrder);
//因为游标还要使用，注意不要关闭数据库
return cursor;
}else if(matcher.match(uri)==QUERY_ONE){
//根据age查询一条数据
long age= ContentUris.parseId(uri);
Cursor cursor = database.query(TABLE_NAME, projection, "age=?", new String[]{age + ""}, null, null, sortOrder);
return cursor;
}else {
Log.e("xmh","query-error:"+uri);
}
return null;

7. 重写insert方法
   
//匹配URI
if(matcher.match(uri)==INSERT){
database.insert(TABLE_NAME,null,values);
}else {
Log.e("xmh","insert-error:"+uri);
}
return null;

8. 重写delete方法
   
//匹配URI
if(matcher.match(uri)==DELETE){
//执行删除并返回受影响行数
return database.delete(TABLE_NAME, selection, selectionArgs);
}else {
Log.e("xmh","delete-error:"+uri);
}
return 0;

9. 重写update方法
   
//匹配UIR
if(matcher.match(uri)==UPDATE){
//执行修改并返回受影响行数
return database.update(TABLE_NAME,values,selection,selectionArgs);
}else {
Log.e("xmh","update-error:"+uri);
}
return 0;

10. 重写getType方法
    
if(matcher.match(uri)==QUERY){
//dir表示一组数据
return "vnd.android.cursor.dir/beanname";
}else if(matcher.match(uri)==QUERY_ONE){
//item表示一项数据
return "vnd.android.cursor.item/beanname";
}else{
Log.e("xmh","type-error:"+uri);
}
return null;


创建内容使用者Module

此例中Module为SampleOfContentProviderOther，以下方法均在Activity中测试
1. 查询数据

//得到内容提供中间件
ContentResolver resolver = getContentResolver();
//生成URI
Uri uri=Uri.parse("content://com.xmh.sampleofcontentprovider/query");
//请求获取游标
Cursor cursor = resolver.query(uri, null, null, null, null);
//处理查询结果
while(cursor.moveToNext()){
String id=cursor.getString(cursor.getColumnIndex("id"));
String name=cursor.getString(cursor.getColumnIndex("name"));
int age = cursor.getInt(cursor.getColumnIndex("age"));
Log.e("xmh","id="+id+",name="+name+"age="+age);
}
//关闭游标
cursor.close();

1. 删除数据

//得到内容提供中间件
ContentResolver resolver = getContentResolver();
//生成URI
Uri uri=Uri.parse("content://com.xmh.sampleofcontentprovider/delete");
//请求删除
int delete = resolver.delete(uri, "id = ?", new String[]{"001"});

1. 更新数据

//得到内容提供中间件
ContentResolver resolver=getContentResolver();
//生成URI
Uri uri=Uri.parse("content://com.xmh.sampleofcontentprovider/update");
//请求修改
ContentValues contentValues = new ContentValues();
contentValues.put("age",50);
int count=resolver.update(uri, contentValues, "id=?", new String[]{"002"});

1. 插入数据

//得到中间件
ContentResolver resolver=getContentResolver();
//生成URI
Uri uri=Uri.parse("content://com.xmh.sampleofcontentprovider/insert");
//请求插入数据
ContentValues contentValues = new ContentValues();
contentValues.put("name", "beda");
resolver.insert(uri, contentValues);

1. 查询单条数据

//得到中间件
ContentResolver resolver=getContentResolver();
//生成URI
Uri uri=Uri.parse("content://com.xmh.sampleofcontentprovider/query/10");
//请求获取游标
Cursor cursor = resolver.query(uri, null, null, null, null);
//处理查询结果
while(cursor.moveToNext()){
String id=cursor.getString(cursor.getColumnIndex("id"));
String name=cursor.getString(cursor.getColumnIndex("name"));
int age = cursor.getInt(cursor.getColumnIndex("age"));
Log.e("xmh","id="+id+",name="+name+"age="+age);
textView.setText("id="+id+",name="+name+",age="+age);
}
//关闭游标
cursor.close();