使用Bootstrap 4在React中進行下拉

Question

當我單擊導航欄中的單個下拉菜單鏈接時，也會顯示或顯示所有下拉菜單鏈接。 如何通過僅顯示一個下拉菜單鏈接來解決此問題？

我嘗試更改指向aria-labelledby的id值

這是我的應用程序的狀態

      state = {
        dropDown: false
      };


      handleDropdown = e => {
            this.setState({ dropDown: !this.state.dropDown });
        };

內部渲染功能

      render() {
        const { dropDown } = this.state;

      /*Conditional statement to select a class base on the state*/

      const dropMenu = dropDown ? 'dropdown-menu show' : 'dropdown-menu';

      /*The two dropdown menu list the displays(both) even when one is clicked*/

    <li className="nav-item dropdown">
                      <Link
                        onClick={this.handleDropdown}
                        className="nav-link dropdown-toggle"
                        href="#"
                        id="navbarDropdown"
                        role="button"
                        data-toggle="dropdown"
                        aria-haspopup="true"
                        aria-expanded="false"
                      >
                        Dropdown
                      </Link>
                      <div className={dropMenu} aria-labelledby="navbarDropdown">
                        <Link className="dropdown-item" to="#">
                          Action
                        </Link>
                        <Link className="dropdown-item" to="#">
                          Another action
                        </Link>
                        <div className="dropdown-divider" />
                        <Link className="dropdown-item" to="#">
                          Something else here
                        </Link>
                      </div>
                    </li>

    <li className="nav-item dropdown">
                      <Link
                        onClick={this.handleDropdown}
                        className="nav-link dropdown-toggle"
                        href="#"
                        id="navbarDropdown"
                        role="button"
                        data-toggle="dropdown"
                        aria-haspopup="true"
                        aria-expanded="false"
                      >
                        Dropdown
                      </Link>
                      <div className={dropMenu} aria-labelledby="navbarDropdown">
                        <Link className="dropdown-item" to="#">
                          Action
                        </Link>
                        <Link className="dropdown-item" to="#">
                          Another action
                        </Link>
                        <div className="dropdown-divider" />
                        <Link className="dropdown-item" to="#">
                          Something else here
                        </Link>
                      </div>
                    </li>
      };

Answer 1

更新的代碼

更改狀態變量，如下所示：

state = {
  dropDownState: [false, false]
};

因為只有兩個li > div所以該數組包含兩個元素，如果菜單項增加，也要增加它們。

然后div看起來像

<div className={dropMenu[0]} aria-labelledby="navbarDropdown">和<div className={dropMenu[1]} aria-labelledby="navbarDropdown">

每個函數綁定看起來像

onClick={() => this.handleDropdown(0)}
onClick={() => this.handleDropdown(1)}

然后，實際功能將變為

handleDropdown = (menuIndex) => {
   let newMenuState = this.state.dropDownState.map((val, index) => {
       if(index === menuIndex) {
           return !val
       } else return val
   });

  this.setState({ dropDownState: newMenuState })
};

請注意，我還沒有運行代碼，但是您應該明白這一點。

舊答案

將值綁定到該函數，而不是調用該函數：

更改

onClick={this.handleDropdown}

至

onClick={() => this.handleDropdown()}

Answer 2

因為您只有1種狀態可以處理顯示和隱藏下拉菜單。 嘗試這樣做：

state = {
  dropDown: {
    link1: false,
    link2: false,
  }
}

handleDropdown = e => {
  const { id } = e.target;

  this.setState(prevState => ({
    dropDown : {
      ...prevState.dropDown,
      [id]: !prevState.dropDown[id],
    }
  }));
}

render() {

const { dropDown } = this.state;

      /*Conditional statement to select a class base on the state*/

      const dropMenu = dropDown ? 'dropdown-menu show' : 'dropdown-menu';

      /*The two dropdown menu list the displays(both) even when one is clicked*/

    <li className="nav-item dropdown">
                      <Link
                        onClick={this.handleDropdown}
                        className="nav-link dropdown-toggle"
                        href="#"
                        id="link1" // name your id same as the variable from state dropDown
                        role="button"
                        data-toggle="dropdown"
                        aria-haspopup="true"
                        aria-expanded="false"
                      >
                        Dropdown
                      </Link>
                      <div className={`dropdown-menu ${dropDown.link1 ? 'show' : ''}`} aria-labelledby="navbarDropdown">
                        <Link className="dropdown-item" to="#">
                          Action
                        </Link>
                        <Link className="dropdown-item" to="#">
                          Another action
                        </Link>
                        <div className="dropdown-divider" />
                        <Link className="dropdown-item" to="#">
                          Something else here
                        </Link>
                      </div>
                    </li>

    <li className="nav-item dropdown">
                      <Link
                        onClick={this.handleDropdown}
                        className="nav-link dropdown-toggle"
                        href="#"
                        id="link2" // name your id same as the variable from state dropDown
                        role="button"
                        data-toggle="dropdown"
                        aria-haspopup="true"
                        aria-expanded="false"
                      >
                        Dropdown
                      </Link>
                      <div className={`dropdown-menu ${dropDown.link2 ? 'show' : ''}`} aria-labelledby="navbarDropdown">
                        <Link className="dropdown-item" to="#">
                          Action
                        </Link>
                        <Link className="dropdown-item" to="#">
                          Another action
                        </Link>
                        <div className="dropdown-divider" />
                        <Link className="dropdown-item" to="#">
                          Something else here
                        </Link>
                      </div>
                    </li>
}

希望它能工作。