ContentProvider的有多个表多个、ContentProvider

2023-09-06 00:22:25 作者：软软

我想实现一个的ContentProvider 的操纵多个表。以下是我试过到目前为止。我写了一个Java 接口的再presents CRUD操作，每个表应在其CRUD类中实现。

I want to implement a ContentProvider that manipulates multiple tables. Here is what I tried so far. I wrote a Java Interface that represents the CRUD operations that every table should implement in its CRUD class.

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);
}

然后我写了摘要 类定义了一个静态 UriMatcher 为的ContentProvider 让每个扩展类这个类应该增加其乌里标识，并规定在接口中的每个方法的实现。

Then I wrote an abstract class that defines a static UriMatcher for the ContentProvider so each class that extends this class should add its Uri that identifies it and provide an implementation for each method in interface.

类看起来是这样的：

public abstract class  ApplicationCRUD  implements CRUDHandler{

    public static final UriMatcher sUriMatcher;

    static {
        sUriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
    }
}

另外，我创建了一个类的每个扩展这个类，并添加了乌里的表 UriMatcher 从抽象类。

Further, I created a class for each table that extends this class and adds its Uri's to the UriMatcher from the abstract class.

下面是一个例子：

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;
    }

}

现在我的的ContentProvider 是这样的：

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);
        }
    }

现在我使用的是 SQLiteOpenHelper 作为私有类的的ContentProvider 而我在的ContentProvider 定义它的一个实例。我应该修改接口，并提供该对象依赖注入来让每个功能使用它来访问数据库的每个CRUD方法？我也想知道你怎么想这个方法：是不是不够好？这会让事情，我试图做有效的？我可以做的修改，以改善这种设计？

Now I am using the SQLiteOpenHelper as a private class in the ContentProvider and I define an instance of it in my ContentProvider. Should I modify the interface and supply each CRUD method that object Dependency Injection to let each function use it to access the database? I also want to know what you think about this approach: Is it good enough? Does it make the thing I am trying to do efficiently? What modification can I do to improve this design?

ContentProvider的有多个表多个、ContentProvider

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