// 监听键盘
        this.keyboardWillShowListener = Keyboard.addListener('keyboardWillShow', this.keyboardDidShow);
        this.keyboardWillHideListener = Keyboard.addListener('keyboardWillHide', this.keyboardDidHide);

 //键盘弹起后执行
    keyboardDidShow = (e) => {
        console.log(e)
        this._scrollView.scrollTo({x: 0, y: e.startCoordinates.height, animated: true});
    }

    //键盘收起后执行
    keyboardDidHide = () => {
        this._scrollView.scrollTo({x: 0, y: 0, animated: true});
    }

 this.keyboardWillShowListener && this.keyboardWillShowListener.remove();
 this.keyboardWillHideListener && this.keyboardWillHideListener.remove();