我想实施一个ContentProvider操作多个表。这是我到目前为止所尝试的。我写了一个JavaInterface表示每个表应在其 CRUD 类中实现的 CRUD 操作。
public interface CRUDHandler {
//UPDATE
int update(Uri uri, ContentValues values, String selection,String[] selectionArgs);
//READ
Cursor query(Uri uri, String[] projection, String selection,String[] selectionArgs, String sortOrder) ;
//CREATE
Uri insert(Uri uri, ContentValues values);
//DELETE
int delete(Uri uri, String selection, String[] selectionArgs);
//get Mime type
String getType(Uri uri);
}
然后我写了一个abstract class定义了一个静态的UriMatcher为了ContentProvider所以每个班级extends这个类应该添加它的Uri它标识它并为接口中的每个方法提供实现。
该类看起来像这样：
public abstract class ApplicationCRUD implements CRUDHandler{
public static final UriMatcher sUriMatcher;
static {
sUriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
}
}
此外，我为每个表创建了一个类extends这个类并添加了它的Uri到UriMatcher来自抽象类。
这是一个例子：
public class Table1CRUD extends ApplicationCRUD {
//Setup Projection Map for Table1
private static HashMap<String , String>sTable1ProjectionMap;
static {
sTable1ProjectionMap.put(ApplicationProviderMetaData.Table1MetaData._ID, ApplicationProviderMetaData.Table1MetaData.TABLE_NAME+"."+ApplicationProviderMetaData.Table1MetaData._ID);
sTable1ProjectionMap.put(ApplicationProviderMetaData.Table1MetaData.COL1, ApplicationProviderMetaData.Table1MetaData.TABLE_NAME+"."+ApplicationProviderMetaData.Table1MetaData.COL1);
sTable1ProjectionMap.put(ApplicationProviderMetaData.Table1MetaData.COL2, ApplicationProviderMetaData.Table1MetaData.TABLE_NAME+"."+ApplicationProviderMetaData.Table1MetaData.COL2);
}
public static final int INCOMING_SINGLE_URI_INDICATOR = 5;
public static final int INCOMING_COLLECTION_URI_INIDICATOR = 6;
static {
//standard URI
sUriMatcher.addURI(ApplicationProviderMetaData.AUTHORITY, "t1", INCOMING_COLLECTION_URI_INIDICATOR);
sUriMatcher.addURI(ApplicationProviderMetaData.AUTHORITY, "t1/#", INCOMING_SINGLE_URI_INDICATOR);
//here add your custom URI
}
@Override
public int update(Uri uri, ContentValues values, String selection,
String[] selectionArgs) {
// TODO Auto-generated method stub
return 0;
}
@Override
public Cursor query(Uri uri, String[] projection, String selection,
String[] selectionArgs, String sortOrder) {
// 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 String getType(Uri uri) {
// TODO Auto-generated method stub
return null;
}
}
Now my ContentProvider看起来像这样：
public class ApplicationProvider extends ContentProvider{
//Define TAG FOR EACH CLASS FOR DEBUGGING
private static final String TAG = "ApplicationProvider";
// Application CRUD Handlers use to support multiple tables inside the content provider
private static Table1CRUD table1CRUD;
private static Table2CRUD table2CRUD;
static {
table1CRUD = new Table1CRUD();
table2CRUD= new Table2CRUD();
}
@Override
public int delete(Uri uri, String selection, String[] selectionArgs) {
int uriMatchResult = ApplicationCRUD.sUriMatcher.match(uri);
//case Table1
if(uriMatchResult == Table1CRUD.INCOMING_COLLECTION_URI_INIDICATOR ||uriMatchResult == Table1CRUD.INCOMING_SINGLE_URI_INDICATOR )
{
return table1CRUD.delete(uri, selection, selectionArgs);
}
case Table2
else if(uriMatchResult == Table2.INCOMING_COLLECTION_URI_INDICATOR|| uriMatchResult ==Table2.INCOMING_SINGLE_URI_INDICATOR){
return table2CRUD.delete(uri, selection, selectionArgs);
}
else{
throw new IllegalArgumentException("Unknown Uri "+uri);
}
}
现在我正在使用SQLiteOpenHelper作为私人课程ContentProvider我在我的中定义了它的一个实例ContentProvider。我是否应该修改接口并提供该对象的每个 CRUD 方法Dependency Injection让每个函数都用它来访问数据库？我还想知道您对这种方法的看法：它足够好吗？它能让我想做的事情变得高效吗？我可以做哪些修改来改进这个设计？
