Java实现图像全屏显示

Java实现图像全屏显示

摘要：

本文包括一个简单的Java程序的源代码，该程序在全屏窗口的中心显示图像(本地文件或者从http://URL下载)，其中使用了AWT Toolkit装载图像，Swing JFrame显示图像。 

兼容性：

Sun Java 1.4或者更高版本 

本程序由一个从标准Swing JFrame类扩展而来的Test1组成。代码的大部分在类的构造方法中：两个简单的事件listener(鼠标listener用于退出程序，窗口listener用于窗口在关闭时终止程序运行)，全屏模式切换代码以及图像数据装载。 

全屏模式切换代码很简单：

this.setUndecorated(true);

this.setVisible(true);

GraphicsEnvironment.getLocalGraphicsEnvironment().getDefaultScreenDevice().setFullScreenWindow(this); 

我们移除窗口的边框和菜单(setUndecorated method)，确信窗口可见(setVisible)，然后调用setFullScreenWindow。你可以在sun.com了解更多高级的全屏API。 

程序装载和显示由命令行参数指定的图像。如果参数由http://开头，就创建一个URL对象，否则参数就作为文件名进行处理，并直接传递给AWT Toolkit的getImage方法。 

Toolkit.getDefaultToolkit().getImage()方法可以装载GIF、JPEG和PNG文件。它接收字符串(文件名)或者URL对象作为其参数。 

Java源代码：

import java.awt.Graphics;

import java.awt.GraphicsEnvironment;

import java.awt.Image;

import java.awt.Toolkit;

import java.awt.event.MouseEvent;

import java.awt.event.MouseListener;

import java.awt.event.WindowAdapter;

import java.awt.event.WindowEvent;

import java.net.MalformedURLException;

import java.net.URL;

 

import javax.swing.JFrame;

 

public class Test1 extends JFrame

{

    // this line is needed to avoid serialization warnings 

    private static final long serialVersionUID = 1L;

 

    Image screenImage;                   // downloaded image 

    int w, h;                                 // Display height and width

 

 

    // Program entry

    public static void main(String[] args) throws Exception

    {

        if (args.length < 1) // by default program will load AnyExample logo

        {

            new Test1("http://www.anyexample.com/i/logo.gif");

        }

        else

        {

            new Test1(args[0]); // or first command-line argument

        }

    }

 

    // Class constructor 

    Test1(String source) throws MalformedURLException

    {

        // Exiting program on window close

        addWindowListener(new WindowAdapter()

        {

            public void windowClosing(WindowEvent e)

            {

                System.exit(0);

            }

        });

 

        // Exitig program on mouse click

        addMouseListener(new MouseListener()

        {

            public void mouseClicked(MouseEvent e) { System.exit(0); }

            public void mousePressed(MouseEvent e) {}

            public void mouseReleased(MouseEvent e) {}

            public void mouseEntered(MouseEvent e) {}

            public void mouseExited(MouseEvent e) {}

        });

 

        // remove window frame 

        this.setUndecorated(true);

 

        // window should be visible

        this.setVisible(true);

 

        // switching to fullscreen mode

        GraphicsEnvironment.getLocalGraphicsEnvironment().getDefaultScreenDevice().setFullScreenWindow(this);

 

        // getting display resolution: width and height

        w = this.getWidth();

        h = this.getHeight();

        System.out.println("Display resolution: " + String.valueOf(w) + "x" + String.valueOf(h));

 

        // loading image 

        if (source.startsWith("http://")) // http:// URL was specified

        {

            screenImage = Toolkit.getDefaultToolkit().getImage(new URL(source));

        }

        else

        {

            screenImage = Toolkit.getDefaultToolkit().getImage(source); // otherwise - file

        }

    }

 

    public void paint (Graphics g)

    {

        if (screenImage != null)                // if screenImage is not null (image loaded and ready)

        {

            g.drawImage(screenImage,         // draw it 

                        w/2 - screenImage.getWidth(this) / 2,      // at the center 

                        h/2 - screenImage.getHeight(this) / 2,     // of screen

                        this);

            // to draw image at the center of screen

            // we calculate X position as a half of screen width minus half of image width

            // Y position as a half of screen height minus half of image height

        }

    }

}  

注意：

如果图像未成功装载，本程序就没有输出。