Question

该程序的目标是将二进制文件读入arraylist然后在gui窗口中显示。有5个索引，我使用curIndex来更新它。我相信我的问题在于refreshUI（）。我不能用新索引更新它。我也不确定如何在刷新中设置字段。如果你能指出我正确的方向，那就太棒了！谢谢你

 ArrayList<SalesAgent> salesForce = new ArrayList<>();
int curIndex = 0;

public RecordViewerPanel() throws ClassNotFoundException, IOException {
    initComponents();
    ObjectInputStream input = new ObjectInputStream(
            new BufferedInputStream(
                    new FileInputStream("sales.bin")));

    while (curIndex < 5) {

        String first = input.readUTF();
        String last = input.readUTF();
        double sales = input.readDouble();
        Date date = (Date) input.readObject();
        salesForce.add(new SalesAgent(first, last, sales, date));
        refreshUI();
    }


}

private void refreshUI() {
salesForce.get(curIndex);
lastTextField.setText(salesForce.getLast());
salesTextField.setText(String.valueOf(salesForce.getSales()));
dateTextField.setText(String.valueOf(salesForce.getDate()));

    jPanel2.repaint();
    curIndex++;

}

/**
 * This method is called from within the constructor to initialize the form.
 * WARNING: Do NOT modify this code. The content of this method is always
 * regenerated by the Form Editor.
 */
@SuppressWarnings("unchecked")


    nextButton.setText(">>");
    nextButton.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            nextButtonActionPerformed(evt);
        }
    });

    javax.swing.GroupLayout jPanel2Layout = new javax.swing.GroupLayout(jPanel2);
    jPanel2.setLayout(jPanel2Layout);
    jPanel2Layout.setHorizontalGroup(
        jPanel2Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(jPanel2Layout.createSequentialGroup()
            .addGroup(jPanel2Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING, false)
                .addGroup(jPanel2Layout.createSequentialGroup()
                    .addGap(24, 24, 24)
                    .addComponent(firstTextField, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addGap(26, 26, 26)
                    .addComponent(lastTextField, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                    .addComponent(salesTextField, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addGap(26, 26, 26)
                    .addComponent(dateTextField, javax.swing.GroupLayout.PREFERRED_SIZE, 134, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addGap(64, 64, 64))
                .addGroup(jPanel2Layout.createSequentialGroup()
                    .addGap(39, 39, 39)
                    .addComponent(jLabel3)
                    .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                    .addGroup(jPanel2Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                        .addGroup(jPanel2Layout.createSequentialGroup()
                            .addGap(31, 31, 31)
                            .addComponent(jLabel4)
                            .addGap(70, 70, 70)
                            .addComponent(jLabel5)
                            .addGap(101, 101, 101)
                            .addComponent(jLabel6))
                        .addGroup(jPanel2Layout.createSequentialGroup()
                            .addGap(254, 254, 254)
                            .addComponent(previousButton)
                            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                            .addComponent(nextButton)))))
            .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
    );
    jPanel2Layout.setVerticalGroup(
        jPanel2Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(jPanel2Layout.createSequentialGroup()
            .addGap(29, 29, 29)
            .addGroup(jPanel2Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                .addComponent(jLabel3)
                .addComponent(jLabel4)
                .addComponent(jLabel5)
                .addComponent(jLabel6))
            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
            .addGroup(jPanel2Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                .addGroup(jPanel2Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(firstTextField, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(lastTextField, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(salesTextField, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addComponent(dateTextField, javax.swing.GroupLayout.PREFERRED_SIZE, 28, javax.swing.GroupLayout.PREFERRED_SIZE))
            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
            .addGroup(jPanel2Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                .addComponent(previousButton)
                .addComponent(nextButton)))
    );

    javax.swing.GroupLayout layout = new javax.swing.GroupLayout(this);
    this.setLayout(layout);
    layout.setHorizontalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addComponent(jPanel1, javax.swing.GroupLayout.Alignment.TRAILING, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
        .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
            .addComponent(jPanel2, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
            .addContainerGap())
    );
    layout.setVerticalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(layout.createSequentialGroup()
            .addComponent(jPanel1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
            .addComponent(jPanel2, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
    );
}// </editor-fold>                        

private void previousButtonActionPerformed(java.awt.event.ActionEvent evt) {                                               
    if (curIndex > 0) {
        curIndex--;
    } else if (curIndex == 0) {
        curIndex = 4;
    }
    salesForce.get(curIndex);
    refreshUI();
}                                              

private void nextButtonActionPerformed(java.awt.event.ActionEvent evt) {                                           
    if (curIndex < 4) {
        curIndex++;
    } else if (curIndex == 4) {
        curIndex = 0;
    }
    salesForce.get(curIndex);
    refreshUI();
}

Answer 1

避免使用＆＃34;魔法＆＃34;数字。使用您的列表大小来帮助您。例如，这很糟糕：

private void nextButtonActionPerformed(java.awt.event.ActionEvent evt) {                                           
    if (curIndex < 4) {
        curIndex++;
    } else if (curIndex == 4) {
        curIndex = 0;
    }
    salesForce.get(curIndex);
    refreshUI();
}

相反它应该是：

private void nextButtonActionPerformed(java.awt.event.ActionEvent evt) { 
  curIndex++;
  curIndex %= salesForce.size(); // mod it by size of your List
  currentSalesAgent = salesForce.get(curIndex);
  // salesForce.get(curIndex); // this throws out the result returned by get(...)
  refreshUI();
}

其中currentSalesAgent是SalesAgent字段，您的类用于获取当前人员的统计信息以供显示。在你的课堂上你要声明

private SalesAgent currentSalesAgent;

请注意，仅调用salseForce.get(curIndex);没有任何用处，因为当方法从List中提取SalesAgent项时，由于您没有将返回的对象分配给任何变量，因此会浪费它。这就是为什么我有：

currentSalesAgent = salesForce.get(curIndex);

然后在您的refreshUI方法中，使用currentSalesAgent：

// salesTextField.setText(String.valueOf(salesForce.getSales())); // this shouldn't compile!
salesTextField.setText(String.valueOf(currentSalesAgent.getSales()));

同样，这对我来说毫无意义：

salesForce.getSales()

你在ArrayList上调用getSales()，而ArrayList没有这样的方法。这怎么可能不会导致编译错误？

修改

我不确定你是否完全了解我，所以我会尽力说明问题。您已在此处将salesForce变量声明为ArrayList变量：

ArrayList<SalesAgent> salesForce = new ArrayList<>();

然后在这里你似乎在这个相同的变量上进行了大量调用，就好像它是一个SalesAgent对象：

lastTextField.setText(salesForce.getLast());
salesTextField.setText(String.valueOf(salesForce.getSales()));
dateTextField.setText(String.valueOf(salesForce.getDate()));

同样，这无法编译，因为ArrayList没有您正在调用的任何这些方法，除非您有第二个同名的 local 变量，salesForce事实上是一个SalesAgent对象，它隐藏了类字段，并且一个你从未向我们展示过你已声明过的字段。如果你这样做，那么不要。你的代码很容易混淆，因为你不应该给出两个完全不同的变量，这些变量包含不同类型的对象同名。

更新gui二元arraylist

1 个答案: