HTTP POST: Mengirim Data ke API

Future<Produk> tambahProduk({required String nama, required int harga}) async {
  final uri = Uri.parse('https://api.contoh.id/produk');
  final response = await http.post(
    uri,
    headers: {'Content-Type': 'application/json'},
    body: jsonEncode({'nama': nama, 'harga': harga}),
  );

  if (response.statusCode == 201) {
    return Produk.fromJson(jsonDecode(response.body) as Map<String, dynamic>);
  }
  throw Exception('Gagal menambah produk: ${response.statusCode}');
}

class _TambahState extends State<Tambah> {
  bool _loading = false;
  final _namaController = TextEditingController();
  final _hargaController = TextEditingController();

  Future<void> _submit() async {
    if (_loading) return;
    setState(() => _loading = true);
    try {
      final produk = await tambahProduk(
        nama: _namaController.text.trim(),
        harga: int.tryParse(_hargaController.text) ?? 0,
      );
      if (!mounted) return;
      ScaffoldMessenger.of(context).showSnackBar(
        SnackBar(content: Text('${produk.nama} tersimpan')),
      );
      Navigator.pop(context, true);
    } catch (e) {
      if (!mounted) return;
      ScaffoldMessenger.of(context).showSnackBar(
        SnackBar(content: Text('Gagal: $e')),
      );
    } finally {
      if (mounted) setState(() => _loading = false);
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text('Tambah Produk')),
      body: Padding(
        padding: const EdgeInsets.all(16),
        child: Column(
          children: [
            TextField(controller: _namaController, decoration: const InputDecoration(labelText: 'Nama')),
            const SizedBox(height: 12),
            TextField(controller: _hargaController, decoration: const InputDecoration(labelText: 'Harga'), keyboardType: TextInputType.number),
            const SizedBox(height: 16),
            SizedBox(
              width: double.infinity,
              child: ElevatedButton(
                onPressed: _loading ? null : _submit,
                child: _loading
                    ? const SizedBox(height: 20, width: 20, child: CircularProgressIndicator(strokeWidth: 2))
                    : const Text('Simpan'),
              ),
            ),
          ],
        ),
      ),
    );
  }
}