尝试这个正则表达式，它将有助于验证输入只接受两个大写字母和7个数值的字符串：

^([A-Z]{2}\d{7})$

例如：

const App = () => {
  const [text, setText] = useState('');
  const [isValid, setIsValid] = useState();

  const handleChange = (event) => {
    const value = event.nativeEvent.text;
    const regex = /^[A-Z]{2}\d{7}$/;
    setText(value);
    if (regex.test(value)) {
      setIsValid(true);
    } else {
      setIsValid(false);
    }
  };

  return (
    <View>
      <TextInput
        placeholder="Enter two capital letters and 7 digits"
        onChange={handleChange}
        value={text}
      />
      {!isValid && <Text>Input string is not valid</Text>}
    </View>
  );
};