AWT Canvas類

介紹

Canvas控件代表一個矩形區域，應用程序可以畫的東西，或者可以由用戶創建的接收輸入。

類的聲明

以下是聲明的java.awt.Canvas類：

public class Canvas extends Component implements Accessible

類的構造函數

S.N.

構造函數& 描述

1

Canvas()
Constructs a new Canvas.

2

Canvas(GraphicsConfiguration config)
Constructs a new Canvas given a GraphicsConfiguration object.

類方法

S.N.

方法& 描述

1

void addNotify()
Creates the peer of the canvas.

2

void createBufferStrategy(int numBuffers)
Creates a new strategy for multi-buffering on this component.

3

void createBufferStrategy(int numBuffers, BufferCapabilities caps)
Creates a new strategy for multi-buffering on this component with the required buffer capabilities.

4

AccessibleContext getAccessibleContext()
Gets the AccessibleContext associated with this Canvas.

5

BufferStrategy getBufferStrategy()
Returns the BufferStrategy used by this component.

6

void paint(Graphics g)
Paints this canvas.

7

void pdate(Graphics g)
Updates this canvas.

繼承的方法

這個類繼承的方法從以下類：

• java.awt.Component

• java.lang.Object

Canvas 實例

選擇使用任何編輯器創建以下java程序 D:/ > AWT > com > yiibai > gui >

AwtControlDemo.java

package com.yiibai.gui; import java.awt.*; import java.awt.event.*; public class AwtControlDemo { private Frame mainFrame; private Label headerLabel; private Label statusLabel; private Panel controlPanel; public AwtControlDemo(){ prepareGUI(); } public static void main(String[] args){ AwtControlDemo awtControlDemo = new AwtControlDemo(); awtControlDemo.showCanvasDemo(); } private void prepareGUI(){ mainFrame = new Frame("Java AWT Examples"); mainFrame.setSize(400,400); mainFrame.setLayout(new GridLayout(3, 1)); mainFrame.addWindowListener(new WindowAdapter() { public void windowClosing(WindowEvent windowEvent){ System.exit(0); } }); headerLabel = new Label(); headerLabel.setAlignment(Label.CENTER); statusLabel = new Label(); statusLabel.setAlignment(Label.CENTER); statusLabel.setSize(350,100); controlPanel = new Panel(); controlPanel.setLayout(new FlowLayout()); mainFrame.add(headerLabel); mainFrame.add(controlPanel); mainFrame.add(statusLabel); mainFrame.setVisible(true); } private void showCanvasDemo(){ headerLabel.setText("Control in action: Canvas"); controlPanel.add(new MyCanvas()); mainFrame.setVisible(true); } class MyCanvas extends Canvas { public MyCanvas () { setBackground (Color.GRAY); setSize(300, 300); } public void paint (Graphics g) { Graphics2D g2; g2 = (Graphics2D) g; g2.drawString ("It is a custom canvas area", 70, 70); } } }

編譯程序，使用命令提示符。到 D:/ > AWT 然後鍵入以下命令。

D:AWT>javac comyiibaiguiAwtControlDemo.java

如果沒有錯誤出現，這意味着編譯成功。使用下面的命令來運行程序。

D:AWT>java com.yiibai.gui.AwtControlDemo

驗證下面的輸出