java - 无法从 SQLite 数据库填充我的 Activity (DrinkActivity)

Question

我不知道我错过了什么，我无法从我的数据库中填充我的 DrinkActivity!

这是我的 SQLiteOpenHelper 类:

public class StarbuzzDatabaseHelper extends SQLiteOpenHelper {

    private static final String DB_NAME = "starbuzz"; // the name of our database
    private static final int DB_VERSION = 2; // the version of the database

    StarbuzzDatabaseHelper(Context context) {
        super(context, DB_NAME, null, DB_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        updateMyDatabase(db, 0, DB_VERSION);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        updateMyDatabase(db, oldVersion, newVersion);
    }

    private static void insertDrink(SQLiteDatabase db, String name, String description,
                                    int resourceId) {
        ContentValues drinkValues = new ContentValues();
        drinkValues.put("NAME", name);
        drinkValues.put("DESCRIPTION", description);
        drinkValues.put("IMAGE_RESOURCE_ID", resourceId);
        db.insert("DRINK", null, drinkValues);
    }

    private void updateMyDatabase(SQLiteDatabase db, int oldVersion, int newVersion) {
        if (oldVersion < 1) {
            db.execSQL("CREATE TABLE DRINK (_id INTEGER PRIMARY KEY AUTOINCREMENT, "
                    + "NAME TEXT, "
                    + "DESCRIPTION TEXT, "
                    + "IMAGE_RESOURCE_ID INTEGER);");
            insertDrink(db, "Latte", "Espresso and steamed milk", R.drawable.latte);
            insertDrink(db, "Cappuccino", "Espresso, hot milk and steamed-milk foam",
                    R.drawable.cappuccino);
            insertDrink(db, "Filter", "Our best drip coffee", R.drawable.filter);
        }
        if (oldVersion < 2) {
            db.execSQL("ALTER TABLE DRINK ADD COLUMN FAVORITE NUMERIC;");
        }
    }
}

和导致 DrinkActivity 的其他 Activity (DrinkCategoryActivity) 在这里:

public class DrinkCategoryActivity extends AppCompatActivity {

    private SQLiteDatabase db;
    private Cursor cursor;

    @Override
    protected void onCreate(Bundle savedInstanceState){
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_drink_category);
        SQLiteOpenHelper starbuzzDatabaseHelper = new StarbuzzDatabaseHelper(this);
        ListView listDrinks = findViewById(R.id.list_drinks);

        try {
            db = starbuzzDatabaseHelper.getReadableDatabase();
            cursor = db.query("DRINK",
                    new String[]{"_id", "NAME"},
                    null, null, null, null, null);
            SimpleCursorAdapter listAdapter = new SimpleCursorAdapter(this,
                    android.R.layout.simple_list_item_1,
                    cursor,
                    new String[]{"NAME"},
                    new int[]{android.R.id.text1},
                    0);
            listDrinks.setAdapter(listAdapter);
        } catch(SQLiteException e) {
            Toast toast = Toast.makeText(this, "Database unavailable", Toast.LENGTH_SHORT);
            toast.show();
        }

        AdapterView.OnItemClickListener itemClickListener =
                new AdapterView.OnItemClickListener(){
                    @Override
                    public void onItemClick(AdapterView<?> listDrinks,
                                            View itemView,
                                            int position,
                                            long id) {
                        //Pass the drink the user clicks on to DrinkActivity
                        Intent intent = new Intent(DrinkCategoryActivity.this,
                                DrinkActivity.class);
                        intent.putExtra(DrinkActivity.EXTRA_DRINK_ID, (int) id);
                        startActivity(intent);
                    }
                };
        listDrinks.setOnItemClickListener(itemClickListener);

    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        cursor.close();
        db.close();
    }
}

最后是DrinkActivity:

public class DrinkActivity extends Activity {


    public static final String EXTRA_DRINK_ID = "drinkId";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_drink);

        int drinkId = Objects.requireNonNull(getIntent().getExtras()).getInt("EXTRA_DRINK_ID");

        SQLiteOpenHelper starbuzzDatabaseHelper = new StarbuzzDatabaseHelper(this);
        try {
            SQLiteDatabase db = starbuzzDatabaseHelper.getReadableDatabase();
            Cursor cursor = db.query ("DRINK",
                    new String[] {"NAME", "DESCRIPTION", "IMAGE_RESOURCE_ID"},
                    "_id = ?",
                    new String[] {Integer.toString(drinkId)},
                    null, null,null);
            if (cursor.moveToFirst()) {
                //Get the drink details from the cursor
                String nameText = cursor.getString(0);
                String descriptionText = cursor.getString(1);
                int photoId = cursor.getInt(2);

                //Populate the drink name
                TextView name = findViewById(R.id.name1);
                name.setText(nameText);

                //Populate the drink description
                TextView description = findViewById(R.id.description1);
                description.setText(descriptionText);

                //Populate the drink image
                ImageView photo = findViewById(R.id.photo1);
                photo.setImageResource(photoId);
                photo.setContentDescription(nameText);
            }

            cursor.close();
            db.close();


        } catch (SQLException e) {
            Toast.makeText(this, "Database unavailable", Toast.LENGTH_LONG).show();
        }
    }
}

Answer 1

首先 DATABASE_NAME 应该是 name.db，您缺少文件的扩展名。

引用: https://developer.android.com/training/data-storage/sqlite

---

另一个重要的事情是如何从 Intent 中检索数据，你不应该使用:

getIntent().getExtras()).getInt("EXTRA_DRINK_ID")

相反，一旦您有了 Intent ，就可以通过这种方式直接提取数据:

Intent intent = getIntent();
int extraId = intent.getExtraInt(DrinkActivity.EXTRA_DRINK_ID);