窗口未調整大小

Question

我正在編寫一種顯示和調整窗口大小的方法，但是由於某種原因它沒有調整其大小。

static void frame(JFrame f) {

    JFrame frame = f;
    int frameWidth = 500;
    int frameHeight = 500;
    Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
    frame.setBounds((int) screenSize.getWidth() - frameWidth, 0, frameWidth, frameHeight);
    frame.setLocationRelativeTo(null);
    frame.setBackground(Color.WHITE);
    frame.setVisible(true);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}

這是我的繪畫方法：

package events;

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class P extends JPanel {

static P g = new P();
int x = 500;
int y = 500;

@Override
public Dimension getPreferredSize() {
    return new Dimension(x, y);

}

public void paintComponent(Graphics g) {

    super.paintComponent(g);

}

}

這是我的主要方法：

    frame.add(P.g);
    P.g.setLayout(null);
    text[0] = new JTextArea(0, 0);
    text[0].setLineWrap(true);
    text[0].setEditable(false);
    JScrollPane scroll = new JScrollPane(text[0]);

    scroll.setBounds(20, 20, 450, 110);
    P.g.add(scroll);

    frame(frame);

Answer 1

在這段代碼中，我們可以看到兩個要點：

• 變量P g = new P()靜態用法P g = new P()
• 沒有對JFrame.pack()調用（引用JFrame.pack()

首先，變量P g = new P()已被初始化，但是在此代碼中，我無法觀察到任何人都會調整與首選大小相關的WIDTH和HEIGTH 。 第二點，此代碼中沒有對JFrame.pack()方法的引用， JFrame.pack()方法最初是從java.awt.Window.pack()繼承的。 此方法很重要，因為在Windows和Frames上使用的方法要調整大小以適合其子組件的首選大小和布局。 pack()方法不僅是調整frame的一種方法。 請參見下面Oracle文檔中的報價：

打包的另一種方法是通過調用setSize或setBounds（也設置幀位置）顯式建立幀大小。 通常，使用pack優於調用setSize，因為pack由框架布局管理器負責框架大小，並且布局管理器擅長調整平台依賴性和其他影響組件大小的因素。

一些有用的鏈接：

• JFrame（Oracle文件）
• 窗口包參考（API）

---

package sample;

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Toolkit;
import javax.swing.JFrame;
import javax.swing.JPanel;

class P extends JPanel {
    static P g = new P();
    int x = 500;
    int y = 500;

    @Override
    public Dimension getPreferredSize() {
        return new Dimension(x, y);

    }

    @Override
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
    }
}

public class MyFrame extends javax.swing.JFrame {
    public MyFrame() { }
    static void frame(JFrame f) {
        JFrame frame = f;
        int frameWidth = 500;
        int frameHeight = 500;
        Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
        frame.setBounds((int) screenSize.getWidth() - frameWidth, 0, frameWidth, frameHeight);
        frame.setLocationRelativeTo(null);
        frame.setBackground(Color.WHITE);
        frame.setVisible(true);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
    public static void main(String args[]) {

        // 1. creating the frame window
        //
        MyFrame myFrame = new MyFrame();
        myFrame.add( P.g );
        P.g.setLayout( null );

        // others usefull  operations
        // configuring others objetcs
        // to be added on P.g

        // text[0] = new JTextArea(0, 0);
        // text[0].setLineWrap(true);
        // text[0].setEditable(false);
        // JScrollPane scroll = new JScrollPane(text[0]);
        // P.g.add(scroll);

        // 2. setting preferred size
        Dimension preferredSize = P.g.getPreferredSize();
        myFrame.setPreferredSize(preferredSize);

        // 3. need apply the pack method (here or any other place)
        // calling your method frame(JFrame)
        frame(myFrame);

        myFrame.setVisible( true );
        myFrame.pack();   
    }             
}

由於平台相關的問題或安全性問題，也許可以將RT異常作為NullPointerException拋出。 見下文：

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at events.P.paintComponent(P.java:82)
at javax.swing.JComponent.paint(Unknown Source)
at javax.swing.JComponent.paintChildren(Unknown Source)
at javax.swing.JComponent.paint(Unknown Source)
at javax.swing.JComponent.paintChildren(Unknown Source)
at javax.swing.JComponent.paint(Unknown Source)
at javax.swing.JLayeredPane.paint(Unknown Source)
at javax.swing.JComponent.paintChildren(Unknown Source)
at javax.swing.JComponent.paintToOffscreen(Unknown Source)
at javax.swing.BufferStrategyPaintManager.paint(Unknown Source)
at javax.swing.RepaintManager.paint(Unknown Source)
at javax.swing.JComponent.paint(Unknown Source)
at java.awt.GraphicsCallback$PaintCallback.run(Unknown Source)
at sun.awt.SunGraphicsCallback.runOneComponent(Unknown Source)
at sun.awt.SunGraphicsCallback.runComponents(Unknown Source)
at java.awt.Container.paint(Unknown Source)
at java.awt.Window.paint(Unknown Source)
at javax.swing.RepaintManager$4.run(Unknown Source)
at javax.swing.RepaintManager$4.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at javax.swing.RepaintManager.paintDirtyRegions(Unknown Source)
at javax.swing.RepaintManager.paintDirtyRegions(Unknown Source)
at javax.swing.RepaintManager.prePaintDirtyRegions(Unknown Source)
at javax.swing.RepaintManager.access$1300(Unknown Source)
at javax.swing.RepaintManager$ProcessingRunnable.run(Unknown Source)
at java.awt.event.InvocationEvent.dispatch(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$400(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)

因此，可以使用該隊列通過EventQueue進行修復， Oracle Docs提供了更多詳細信息

根據以下代碼，解決將代碼包裝到具有EventQueue的main方法內的問題：

public static void main(String args[]) {

    java.awt.EventQueue.invokeLater(new Runnable() {
        @Override
        public void run() {

            // 1. creating the frame window
            //
            MyFrame myFrame = new MyFrame();
            myFrame.add( P.g );
            P.g.setLayout( null );

            // others usefull  operations
            // configuring others objetcs
            // to be added on P.g

            // text[0] = new JTextArea(0, 0);
            // text[0].setLineWrap(true);
            // text[0].setEditable(false);
            // JScrollPane scroll = new JScrollPane(text[0]);
            // P.g.add(scroll);

            // 2. setting preferred size
            Dimension preferredSize = P.g.getPreferredSize();
            myFrame.setPreferredSize(preferredSize);

            // 3. need apply the pack method (here or any other place)
            // calling your method frame(JFrame)
            frame(myFrame);

            myFrame.setVisible( true );
            myFrame.pack();   

        }
    });

}     

PS：@Skillet，對任何對您提供的代碼的誤解感到抱歉。