我的应用中有一个内容提供商，我真的不喜欢它:-)。在阅读了诸如the official one和this unofficial one等文章之后创建了提供者。
我真正不喜欢的是提供程序类中的重复数量（请参阅下面的非常简化的代码）。即使是两个（或四个，这取决于你如何计算）内容类型，代码也太多了。
我考虑过另一条路线：内容提供商的原始SQL查询，但不确定这是否会变得更优雅。
请建议更好的方法来创建Android内容提供商，然后是下面代码中的内容提供商。
public abstract class BaseProvider extends ContentProvider
{
protected DatabaseHelper m_helper;
protected static class DatabaseHelper extends SQLiteOpenHelper
{
private static final String DATABASE_NAME = "my.db";
private static final int DATABASE_VERSION = 4;
public DatabaseHelper(Context context)
{
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db)
{
FolderTable.onCreate(db);
TrackTable.onCreate(db);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)
{
FolderTable.onUpgrade(db, oldVersion, newVersion);
TrackTable.onUpgrade(db, oldVersion, newVersion);
}
}
@Override
public boolean onCreate()
{
m_helper = new DatabaseHelper(getContext());
return true;
}
// ...
}
public class MyProvider extends BaseProvider
{
private static final UriMatcher sURIMatcher = new UriMatcher(UriMatcher.NO_MATCH);
private static final int FOLDERS = 10;
private static final int FOLDER_ID = 20;
private static final int TRACKS = 30;
private static final int TRACK_ID = 40;
private static final String FOLDERS_BASE_PATH = "folders";
private static final String TRACKS_BASE_PATH = "tracks";
public static final String AUTHORITY = ".contentprovider.MyProvider";
private static final String CONTENT_URI_BASE = "content://" + AUTHORITY + "/";
public static final Uri FOLDERS_CONTENT_URI = Uri.parse(CONTENT_URI_BASE + FOLDERS_BASE_PATH);
public static final Uri TRACKS_CONTENT_URI = Uri.parse(CONTENT_URI_BASE + TRACKS_BASE_PATH);
static
{
sURIMatcher.addURI(AUTHORITY, FOLDERS_BASE_PATH, FOLDERS);
sURIMatcher.addURI(AUTHORITY, FOLDERS_BASE_PATH + "/#", FOLDER_ID);
sURIMatcher.addURI(AUTHORITY, TRACKS_BASE_PATH, TRACKS);
sURIMatcher.addURI(AUTHORITY, TRACKS_BASE_PATH + "/#", TRACK_ID);
}
@Override
public Cursor query(Uri uri, String[] projection, String selection,
String[] selectionArgs, String sortOrder)
{
SQLiteQueryBuilder queryBuilder = new SQLiteQueryBuilder();
int uriType = sURIMatcher.match(uri);
switch (uriType)
{
case FOLDERS:
queryBuilder.setTables(getTablesForFolders());
break;
case FOLDER_ID:
queryBuilder.setTables(FolderTable.TABLE_NAME);
queryBuilder.appendWhere(FolderTable.COLUMN_ID + "=" + uri.getLastPathSegment());
break;
case TRACKS:
queryBuilder.setTables(getTablesForTracks());
break;
case TRACK_ID:
queryBuilder.setTables(TrackTable.TABLE_NAME);
queryBuilder.appendWhere(TrackTable.COLUMN_ID + "=" + uri.getLastPathSegment());
break;
default:
throw new IllegalArgumentException("Unknown URI: " + uri);
}
SQLiteDatabase db = m_helper.getWritableDatabase();
if (db == null)
return null;
Cursor cursor = queryBuilder.query(db, projection, selection, selectionArgs, null, null, sortOrder);
if (cursor == null)
return null;
setNotificationUri(cursor, uri);
return cursor;
}
// ....
}
答案 0 :(得分：-1)
使用不同的类来实现ContentProvider和DatabaseHelper。看到的例子不是你的例子不同的东西，但你会通过看到它来获得想法。
DatabaseHelper.java
public class DatabaseHelper extends SQLiteOpenHelper{
private static final String name="mybooks.sdb";
private static final int version=1;
private static final CursorFactory factory=null;
public DatabaseHelper(Context context)
{
super(context,name,factory,version);
}
@Override
public void onCreate(SQLiteDatabase database) {
// TODO Auto-generated method stub
database.execSQL("create table mybooks(code INTEGER PRIMARY KEY AUTOINCREMENT,name TEXT,author TEXT)");
}
@Override
public void onUpgrade(SQLiteDatabase arg0, int arg1, int arg2) {
// TODO Auto-generated method stub
}
public long insert(ContentValues contentValues)
{
long x;
SQLiteDatabase database=this.getWritableDatabase();
x=database.insert("mybooks",null, contentValues);
database.close();
return x;
}
public Cursor query(String[] columns,String whereClause,String[] replaceQuestionMarksWith,String orderBy)
{
SQLiteDatabase database=this.getReadableDatabase();
return database.query("mybooks", columns, whereClause, replaceQuestionMarksWith, null, null, orderBy);
}
public int update(ContentValues contentValues,String whereClause,String[] replaceQuestionMarksWith)
{
SQLiteDatabase database=this.getWritableDatabase();
int numberOfRecordsUpdated=database.update("mybooks", contentValues, whereClause, replaceQuestionMarksWith);
database.close();
return numberOfRecordsUpdated;
}
public int delete(String whereClause,String[] replaceQuestionMarksWith)
{
SQLiteDatabase database=this.getWritableDatabase();
int numberOfRecordsDeleted=database.delete("mybooks", whereClause, replaceQuestionMarksWith);
database.close();
return numberOfRecordsDeleted;
}
}
和ContentProvider.java为
public class MyBookProvider extends ContentProvider{
private DatabaseHelper databaseHelper;
private static final UriMatcher uriMatcher;
private static final int INCOMING_BOOK_COLLECTION_URI_INDICATOR = 1;
private static final int INCOMING_ONE_BOOK_URI_INDICATOR = 2;
static {
uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
uriMatcher.addURI(LibraryContentProviderMetaData.AUTHORITY, "books",INCOMING_BOOK_COLLECTION_URI_INDICATOR);
uriMatcher.addURI(LibraryContentProviderMetaData.AUTHORITY, "books/#",INCOMING_ONE_BOOK_URI_INDICATOR);
}
@Override
public String getType(Uri uri)
{
String mimeType;
switch(uriMatcher.match(uri))
{
case INCOMING_BOOK_COLLECTION_URI_INDICATOR:
mimeType=LibraryContentProviderMetaData.CONTENT_TYPE;
break;
case INCOMING_ONE_BOOK_URI_INDICATOR:
mimeType=LibraryContentProviderMetaData.CONTENT_ITEM_TYPE;
break;
default:throw new IllegalArgumentException("Invalid URI"+uri);
}
return mimeType;
}
@Override
public Uri insert(Uri uri, ContentValues contentValues) {
// TODO Auto-generated method stub
if (uriMatcher.match(uri) != INCOMING_BOOK_COLLECTION_URI_INDICATOR)
{
throw new IllegalArgumentException("Invalid URI " + uri);
}
long x = databaseHelper.insert(contentValues);
return Uri.parse("content//com.lib.mybooks.MyBookProvider/books/" + x);
}
@Override
public boolean onCreate() {
databaseHelper = new DatabaseHelper(getContext());
return true;
}
@Override
public Cursor query(Uri uri, String[] columns, String whereClause,String[] replaceQuestionMarksWith, String orderBy)
{
switch (uriMatcher.match(uri))
{
case INCOMING_BOOK_COLLECTION_URI_INDICATOR:break;
case INCOMING_ONE_BOOK_URI_INDICATOR:whereClause = "code=?";
replaceQuestionMarksWith = new String[] { uri.getPathSegments().get(1) };
break;
default:throw new IllegalArgumentException("Invalid URI " + uri);
}
Cursor cursor = databaseHelper.query(columns, whereClause,replaceQuestionMarksWith, orderBy);
return cursor;
}
@Override
public int update(Uri uri, ContentValues contentValues, String whereClause, String[] replaceQuestionMarksWith)
{
if(uriMatcher.match(uri)!=INCOMING_BOOK_COLLECTION_URI_INDICATOR)
{
throw new IllegalArgumentException("Invalid URI "+uri);
}
return databaseHelper.update(contentValues, whereClause,replaceQuestionMarksWith);
}
@Override
public int delete(Uri uri, String whereClause, String[] replaceQuestionMarksWith)
{
if(uriMatcher.match(uri)!=INCOMING_BOOK_COLLECTION_URI_INDICATOR)
{
throw new IllegalArgumentException("Invalid URI "+uri);
}
return databaseHelper.delete(whereClause, replaceQuestionMarksWith);
}
}