//按随机排序背诵
 private void button_random_Click(object sender, EventArgs e)
 {
     if (listType == "" || (listType != "myWordTable" && listType != "idiom" && listNum == 0))
     {
         MessageBox.Show("请选择一个背诵列表");
     }
     else
     {
         orderType = "random";
         Form_recite f_recite = new Form_recite(listType, listNum, orderType);
         listNum = 0;
         f_recite.ShowDialog();
     }
 }
 //按词频背诵
 private void button_f_Click(object sender, EventArgs e)
 {
     if (listType == "" || (listType != "myWordTable" && listType != "idiom" && listNum == 0))
     {
         MessageBox.Show("请选择一个背诵列表");
     }
     else if (listType == "myWordTable" || listType == "MyList")
     {
         MessageBox.Show("该列表不支持按词频背诵");
     }
     else
     {
         orderType = "frequency";
         Form_recite f_recite = new Form_recite(listType, listNum, orderType);
         listNum = 0;
         f_recite.ShowDialog();
     }
 }