Java AWT Canvas用法及代碼示例

Canvas 類是Java AWT 的一部分。畫布是一個空白的矩形區域，用戶可以在其中繪製或捕獲用戶的輸入。 Canvas類繼承了Component類。
Canvas類的構造函數有：

Canvas()：創建一個新的空白畫布。
畫布(圖形配置c)：創建具有指定圖形配置的新畫布。

Commonly used Methods in Canvas Class

方法	解釋
addNotify()	創建畫布的對等點。
createBufferStrategy(int n)	在此組件上為 multi-buffering 創建新策略。
createBufferStrategy(int n, BufferCapabilities c)	在此組件上創建 multi-buffering 的新策略，並具有所需的緩衝區函數
getBufferStrategy()	返回此組件使用的BufferStrategy。
paint(Graphics g)	繪製該組件。
update(Graphics g)	更新此畫布。

以下示例程序旨在說明Canvas類的使用：

程序1:創建畫布並在畫布上繪製。

Java


// Java Program to create a to create
// a canvas and paint the canvas
import java.awt.*;
import javax.swing.*;
class canvas extends JFrame {
    // constructor
    canvas()
    {
        super("canvas");
        // create a empty canvas
        Canvas c = new Canvas() {
            // paint the canvas
            public void paint(Graphics g)
            {
                // set color to red
                g.setColor(Color.red);
                // set Font
                g.setFont(new Font("Bold", 1, 20));
                // draw a string
                g.drawString("This is a canvas", 100, 100);
            }
        };
        // set background
        c.setBackground(Color.black);
        add(c);
        setSize(400, 300);
        show();
    }
    // Main Method
    public static void main(String args[])
    {
        canvas c = new canvas();
    }
}

Output:

程序2:創建畫布並向畫布添加鼠標偵聽器(在畫布上單擊或拖動鼠標的位置將出現一個半徑為 5 的圓)。

Java


// Java Program to create a 
// canvas and mouse listener to the 
// canvas ( a circle of radius 5 will appear
// at the points where mouse are clicked or
//  dragged on the canvas)
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
class canvas extends JFrame implements MouseListener, MouseMotionListener {
    // create a canvas
    Canvas c;
    // constructor
    canvas()
    {
        super("canvas");
        // create a empty canvas
        c = new Canvas() {
            public void paint(Graphics g)
            {
            }
        };
        // set background
        c.setBackground(Color.black);
        // add mouse listener
        c.addMouseListener(this);
        c.addMouseMotionListener(this);
        add(c);
        setSize(400, 300);
        show();
    }
    // mouse listener  and mouse motion listener methods
    public void mouseClicked(MouseEvent e)
    {
        Graphics g = c.getGraphics();
        g.setColor(Color.red);
        // get X and y position
        int x, y;
        x = e.getX();
        y = e.getY();
        // draw a Oval at the point 
        // where mouse is moved
        g.fillOval(x, y, 5, 5);
    }
    public void mouseMoved(MouseEvent e)
    {
    }
    public void mouseDragged(MouseEvent e)
    {
        Graphics g = c.getGraphics();
        g.setColor(Color.red);
        // get X and y position
        int x, y;
        x = e.getX();
        y = e.getY();
        // draw a Oval at the point where mouse is moved
        g.fillOval(x, y, 5, 5);
    }
    public void mouseExited(MouseEvent e)
    {
    }
    public void mouseEntered(MouseEvent e)
    {
    }
    public void mouseReleased(MouseEvent e)
    {
    }
    public void mousePressed(MouseEvent e)
    {
    }
    // main class
    public static void main(String args[])
    {
        canvas c = new canvas();
    }
}

Output:

參考：https://docs.oracle.com/javase/7/docs/api/java/awt/Canvas.html

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注：本文由純淨天空篩選整理自andrew1234大神的英文原創作品 Java AWT | Canvas Class。非經特殊聲明，原始代碼版權歸原作者所有，本譯文未經允許或授權，請勿轉載或複製。