基本GUI鼠标侦听器任务

Question

我刚开始使用Java的GUI东西，所以我的理解并不是很好。我试图生成一个程序，用户可以拖动鼠标，并可以同时生成一个矩形。我试图这样做，但我面临着范围问题。任何意见将是有益的。我附上了我认为是我的代码的相关部分。

<form>
                <div class="input-group">
                    <span class="input-group-addon" id="basic-addon1">Name:</span>
                    <input type="text" class="form-control" placeholder="Ex.: John" aria-describedby="basic-addon1" id="name-input">
                </div>

                
                <div class="form-group">
                    <label for="sel1">Place:</label>
                    <select class="form-control" id="sel1" id="place-input">
                      <option value="1">Fixed</option>
                      <option value="2">Mobile</option>
                    </select>
                </div>

                <div class="form-group">
                    <label for="sel2">Technician:</label>
                     <select class="form-control" id="technician-input">
                          <option value="1">Brandon</option>
                          <option value="2">Justin</option>
                          <option value="3">Ryan</option>
                          <option value="4">Tyler</option>
                     </select>
                </div>

        </form>


   

}

   void draw(Graphics g)

{ 


    int canvaswidth= canvas.getWidth();
    int canvasheight=canvas.getHeight();


    g.setColor(new Color(0.8F, 0.8F, 0.8F));




    for(int j=0;j<canvas.getHeight();j = j+10) {

            g.drawLine(0,j,canvas.getWidth(),j);

    }

    for(int i=0;i<canvas.getWidth();i=i+10){

        g.drawLine(i, 0, i,canvas.getHeight());
    }

    for(int k=0;k<canvas.getHeight();k=k+50){
     g.setColor(new Color(0.6F, 0.6F, 0.6F));
        g.drawLine(0, k, canvas.getWidth(), k);
    }

    for(int l=0;l<canvas.getWidth();l=l+50){

        g.drawLine(l, 0, l, canvas.getHeight());
}

    g.setColor(Color.red);