componentWillUnmount() {
    this.keyboardDidShowListener.remove();
    this.keyboardDidHideListener.remove();
}

componentWillMount() {
    this.keyboardDidShowListener = Keyboard.addListener(‘keyboardDidShow‘, this._keyboardDidShow.bind(this));
    this.keyboardDidHideListener = Keyboard.addListener(‘keyboardDidHide‘, this._keyboardDidHide.bind(this));
}

_keyboardDidShow(e) {
    async function run(self) {
        await  self.setState({
            keyboardHeight: e.endCoordinates.height
        });
        self.refs.scroll.scrollTo({
            x: 0, y: self.state.keyboardHeight, animated: true
        })
    }

    run(this);
}

_keyboardDidHide(e) {
    this.setState({
        keyboardHeight: 0
    })
}

react native獲取鍵盤高度