Android Studio SQLite实现收藏功能

实现收藏功能，需要使用Android Studio中内置的SQLite数据库来存储用户收藏的数据。下面是一个简单的实现步骤：

1. 创建数据库表

在SQLite数据库中创建一个收藏表，其中包含收藏的id、名称、描述和图片等字段。可以使用以下代码创建表：

public class DBHelper extends SQLiteOpenHelper {

    private static final int DB_VERSION = 1;
    private static final String DB_NAME = "my_database";
    private static final String TABLE_NAME = "favorites";

    private static final String KEY_ID = "id";
    private static final String KEY_NAME = "name";
    private static final String KEY_DESCRIPTION = "description";
    private static final String KEY_IMAGE = "image";

    private static final String CREATE_TABLE = "CREATE TABLE " + TABLE_NAME + " ("
            + KEY_ID + " INTEGER PRIMARY KEY,"
            + KEY_NAME + " TEXT,"
            + KEY_DESCRIPTION + " TEXT,"
            + KEY_IMAGE + " BLOB"
            + ")";

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

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL(CREATE_TABLE);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME);
        onCreate(db);
    }
}

2. 实现添加收藏

在用户点击“添加收藏”按钮时，将用户收藏数据插入到SQLite数据库中。可以使用以下代码实现：

public class FavoritesActivity extends AppCompatActivity {

    private EditText mNameEditText;
    private EditText mDescriptionEditText;
    private ImageView mImageView;

    private byte[] mImageBytes;

    private DBHelper mDBHelper;

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

        mNameEditText = findViewById(R.id.name_edit_text);
        mDescriptionEditText = findViewById(R.id.description_edit_text);
        mImageView = findViewById(R.id.image_view);

        mDBHelper = new DBHelper(this);
    }

    public void onAddFavoriteClick(View view) {
        String name = mNameEditText.getText().toString();
        String description = mDescriptionEditText.getText().toString();

        // 插入数据到数据库中
        SQLiteDatabase db = mDBHelper.getWritableDatabase();
        ContentValues values = new ContentValues();
        values.put(DBHelper.KEY_NAME, name);
        values.put(DBHelper.KEY_DESCRIPTION, description);
        values.put(DBHelper.KEY_IMAGE, mImageBytes);
        db.insert(DBHelper.TABLE_NAME, null, values);

        Toast.makeText(this, "添加成功", Toast.LENGTH_SHORT).show();
        finish();
    }

    public void onImageClick(View view) {
        // 选择图片
        Intent intent = new Intent(Intent.ACTION_PICK, MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
        startActivityForResult(intent, 1);
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);

        if (requestCode == 1 && resultCode == RESULT_OK && data != null) {
            // 获取选择的图片
            Uri uri = data.getData();
            try {
                Bitmap bitmap = MediaStore.Images.Media.getBitmap(getContentResolver(), uri);
                mImageView.setImageBitmap(bitmap);

                // 将图片转换为字节数组
                ByteArrayOutputStream baos = new ByteArrayOutputStream();
                bitmap.compress(Bitmap.CompressFormat.PNG, 100, baos);
                mImageBytes = baos.toByteArray();

            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

3. 实现查询收藏

在用户进入“我的收藏”页面时，从SQLite数据库中查询出所有收藏的数据并显示到RecyclerView中。可以使用以下代码实现：

public class MyFavoritesActivity extends AppCompatActivity {

    private RecyclerView mRecyclerView;
    private FavoritesAdapter mAdapter;

    private List<FavoriteItem> mFavoriteItems = new ArrayList<>();

    private DBHelper mDBHelper;

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

        mRecyclerView = findViewById(R.id.recycler_view);
        mAdapter = new FavoritesAdapter(mFavoriteItems);
        mRecyclerView.setLayoutManager(new LinearLayoutManager(this));
        mRecyclerView.setAdapter(mAdapter);

        mDBHelper = new DBHelper(this);

        // 查询数据库中的数据
        SQLiteDatabase db = mDBHelper.getReadableDatabase();
        Cursor cursor = db.query(DBHelper.TABLE_NAME, null, null, null, null, null, null);
        if (cursor.moveToFirst()) {
            do {
                int id = cursor.getInt(cursor.getColumnIndex(DBHelper.KEY_ID));
                String name = cursor.getString(cursor.getColumnIndex(DBHelper.KEY_NAME));
                String description = cursor.getString(cursor.getColumnIndex(DBHelper.KEY_DESCRIPTION));
                byte[] imageBytes = cursor.getBlob(cursor.getColumnIndex(DBHelper.KEY_IMAGE));

                // 将查询到的数据添加到列表中
                FavoriteItem item = new FavoriteItem(id, name, description, imageBytes);
                mFavoriteItems.add(item);

            } while (cursor.moveToNext());
        }

        mAdapter.notifyDataSetChanged();
    }

    private class FavoritesAdapter extends RecyclerView.Adapter<FavoritesAdapter.ViewHolder> {

        private List<FavoriteItem> mItems;

        public FavoritesAdapter(List<FavoriteItem> items) {
            mItems = items;
        }

        @NonNull
        @Override
        public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
            View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_favorite, parent, false);
            return new ViewHolder(view);
        }

        @Override
        public void onBindViewHolder(@NonNull ViewHolder holder, int position) {
            FavoriteItem item = mItems.get(position);
            holder.mNameTextView.setText(item.getName());
            holder.mDescriptionTextView.setText(item.getDescription());

            if (item.getImageBytes() != null) {
                Bitmap bitmap = BitmapFactory.decodeByteArray(item.getImageBytes(), 0, item.getImageBytes().length);
                holder.mImageView.setImageBitmap(bitmap);
            }
        }

        @Override
        public int getItemCount() {
            return mItems.size();
        }

        public class ViewHolder extends RecyclerView.ViewHolder {

            private TextView mNameTextView;
            private TextView mDescriptionTextView;
            private ImageView mImageView;

            public ViewHolder(@NonNull View itemView) {
                super(itemView);

                mNameTextView = itemView.findViewById(R.id.name_text_view);
                mDescriptionTextView = itemView.findViewById(R.id.description_text_view);
                mImageView = itemView.findViewById(R.id.image_view);
            }
        }
    }
}

以上就是使用Android Studio内置的SQLite数据库实现收藏功能的步骤。