ScrollBar in JTextArea

Question

我想在文本区域中创建一个滚动条，但是如果我将JPanel布局设置为null，滚动条将不会显示！

我试过

JScrollPane scrollbar1 = 
  new JScrollPane(
    ta1,JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED,
    JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);

但是没有工作，因为空布局.

以下是我的当前代码：

import javax.swing.*;

import java.awt.*;
public class app extends JFrame {

    public static void main(String[] args)
    {
        new app();
    }

    public app()
    {
        this.setSize(400,400);
        this.setLocation(0,0);
        this.setResizable(false);
        this.setTitle("Application");           
        JPanel painel = new JPanel(null);           
        // Creating the Input
        JTextField tf1 = new JTextField("Some random text", 15);            
        tf1.setBounds(5,5,this.getWidth()-120,20);
        tf1.setColumns(10);
        tf1.setText("Omg");         
        painel.add(tf1);            
        // Creating the button          
        JButton button1 = new JButton("Send");          
        button1.setBounds(290, 5, 100, 19);         
        painel.add(button1);            
        // Creating the TextArea            
        JTextArea ta1 = new JTextArea(15, 20);
        JScrollPane scr = new JScrollPane();
        ta1.setBounds(5, 35, 385, 330);
        ta1.setLineWrap(true);
        ta1.setWrapStyleWord(true);         
        painel.add(ta1);
        this.add(painel);
        this.setVisible(true);
    }
}

我想让它正常工作。如果有人能帮我，请在下面留言！

Answer 1

我已经纠正了所有的问题，以下是工作守则。请阅读有关更改的评论。

import javax.swing.*;

import java.awt.*;

public class app extends JFrame {

    public static void main(String[] args) {
        new app();
    }

    public app() {
        this.setSize(400, 400);
        this.setLocation(0, 0);
        this.setResizable(false);
        this.setTitle("Application");
        JPanel painel = new JPanel(null);
        // Creating the Input
        JTextField tf1 = new JTextField("Some random text", 15);
        tf1.setBounds(5, 5, this.getWidth() - 120, 20);
        tf1.setColumns(10);
        tf1.setText("Omg");

        // resultsTA,JScrollPane.VERTICAL_SCROLLBAR_ALWAYS,JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);
        painel.add(tf1);
        // Creating the button
        JButton button1 = new JButton("Send");
        button1.setBounds(290, 5, 100, 19);
        painel.add(button1);
        // Creating the TextArea
        JTextArea ta1 = new JTextArea(15, 20);
        JScrollPane scr = new JScrollPane(ta1,
                JScrollPane.VERTICAL_SCROLLBAR_ALWAYS,
                JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);// Add your text area to scroll pane 
        ta1.setBounds(5, 35, 385, 330);
        ta1.setLineWrap(true);
        ta1.setWrapStyleWord(true);
        scr.setBounds(20, 30, 100, 40);// You have to set bounds for all the controls and containers incas eof null layout
        painel.add(scr);// Add you scroll pane to container
        this.add(painel);
        this.setVisible(true);
    }
}

编辑。请阅读oracle关于Java的教程。开始使用适当的布局管理器..。希望它能帮上忙

Answer 2

您必须将您的JTextArea传递给您的JScrollPane构造函数，然后将JScrollPane对象添加到您的Container中，而不是只添加JTextArea。所以看起来是这样的：

JScrollPane scr = new JScrollPane(ta1);
panel.add(scr);

Answer 3

If someone can help me, leave a comment below please!

• 为什么你要用你的头墙砸碎，JScrollPane被指定为动态的，可调整大小的LayoutManager，AbsoluteLayout可以打破它的基本特性
• 从顶上开始

1. `public class app extends JFrame {`

    - `public class App {` ---> Java Naming Conventions
    - and not extends anything, create `JFrame` as local variable

​

1. `new app();` ---> se Oracle tutorial Initial Thread
2. create another `JPanel`, put there `JTextField` and `JButton` 
3. did you overlay something `tf1.setBounds(5,5,this.getWidth()-120,20);`
4. `NullLayout` doesn't works correctly without using `Insets`
5. change built\_in `FlowLayout` for `JPanel painel = new JPanel(null);` to `BorderLayout`, there put `JScrollPane` with `JTextArea` to `CENTER area`
6. you can to put `JScrollPane` with `JTextArea` to `JFrames CENTER area` directly and another `JPanel` with `JTextField` and `JButton` to `SOUTH` or `NORTH`, `JFrame` has `BorderLayout` implemented in API
7. `JScrollPane` showing `JScrollbars` only in the case that its `Dimension` is smaller than `JComponent` placed there
8. use `JFrame.pack()` instead of `setSize`, this line should be before `setVisible`

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