Android实验：contentprovider 实验+SQLite 数据库的实现

import android.content.ContentProvider;
import android.content.ContentValues;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.net.Uri;
 
public class MyContentProvider extends ContentProvider {
    private SQLiteDatabase db;
 
    private static final String DATABASE_NAME = "mydb.db";
    private static final int DATABASE_VERSION = 1;
    private static final String TABLE_NAME = "mytable";
 
    private static final String CREATE_TABLE_STMT =
        "CREATE TABLE " + TABLE_NAME + " (_id INTEGER PRIMARY KEY, name TEXT);";
 
    private static class DatabaseHelper extends SQLiteOpenHelper {
        DatabaseHelper(ContentProvider provider) {
            super(provider.getContext(), DATABASE_NAME, null, DATABASE_VERSION);
        }
 
        @Override
        public void onCreate(SQLiteDatabase db) {
            db.execSQL(CREATE_TABLE_STMT);
        }
 
        @Override
        public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
            // Implement schema migration logic if needed
        }
    }
 
    @Override
    public boolean onCreate() {
        DatabaseHelper helper = new DatabaseHelper(this);
        db = helper.getWritableDatabase();
        return (db == null) ? false : true;
    }
 
    @Override
    public Cursor query(Uri uri, String[] projection, String selection,
                        String[] selectionArgs, String sortOrder) {
        return db.query(TABLE_NAME, projection, selection, selectionArgs, null, null, sortOrder);
    }
 
    @Override
    public String getType(Uri uri) {
        // Implement if needed, or throw UnsupportedOperationException
        throw new UnsupportedOperationException("Not yet implemented");
    }
 
    @Override
    public Uri insert(Uri uri, ContentValues values) {
        long rowID = db.insert(TABLE_NAME, "", values);
        return Uri.parse(CONTENT_URI + "/" + rowID);
    }
 
    @Override
    public int delete(Uri uri, String selection, String[] selectionArgs) {
        return db.delete(TABLE_NAME, selection, selectionArgs);
    }
 
    @Override
    public