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POContentProvider with multiple tables
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copied!<p>I want to implement a <code>ContentProvider</code> that manipulates multiple tables. Here is what I tried so far. I wrote a Java <code>Interface</code> that represents the CRUD operations that every table should implement in its CRUD class. </p> <pre><code>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); } </code></pre> <p>Then I wrote an <code>abstract</code> <code>class</code> that defines a static <code>UriMatcher</code> for the <code>ContentProvider</code> so each class that <code>extends</code> this class should add its <code>Uri</code> that identifies it and provide an implementation for each method in interface.</p> <p>The class looks like this:</p> <pre><code>public abstract class ApplicationCRUD implements CRUDHandler{ public static final UriMatcher sUriMatcher; static { sUriMatcher = new UriMatcher(UriMatcher.NO_MATCH); } } </code></pre> <p>Further, I created a class for each table that <code>extends</code> this class and adds its <code>Uri</code>'s to the <code>UriMatcher</code> from the abstract class.</p> <p>Here is an example:</p> <pre><code>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; } } </code></pre> <p>Now my <code>ContentProvider</code> looks like this: </p> <pre><code>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); } } </code></pre> <p>Now I am using the <code>SQLiteOpenHelper</code> as a private class in the <code>ContentProvider</code> and I define an instance of it in my <code>ContentProvider</code>. Should I modify the interface and supply each CRUD method that object <code>Dependency Injection</code> 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?</p>

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