自定义的SWT控件：缩略图

效果图：


为了在SWT中实现像Windows桌面图标那样的效果，自定义了一个控件，该控件继承自org.eclipse.swt.widgets.Composite，由一个缩略图标(CLabel)和一个图标名称(Label)构成。
缩略图是由图片文件提供，并缩放到固定尺寸。

创建该控件需要向其构造函数传递一个Image和String，分别是缩略图的原图和即将在图标下方显示的名称。

控件的代码如下，很简单：

import java.io.File;
import org.eclipse.jface.resource.ImageDescriptor;
import org.eclipse.swt.SWT;
import org.eclipse.swt.custom.CLabel;
import org.eclipse.swt.events.MouseListener;
import org.eclipse.swt.events.PaintEvent;
import org.eclipse.swt.events.PaintListener;
import org.eclipse.swt.graphics.Image;
import org.eclipse.swt.graphics.Point;
import org.eclipse.swt.graphics.Rectangle;
import org.eclipse.swt.layout.FillLayout;
import org.eclipse.swt.layout.GridData;
import org.eclipse.swt.layout.GridLayout;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Label;
import org.eclipse.swt.widgets.Shell;

public class Thumbnails extends Composite {
	private CLabel cLabelImage;
	private Image image;
	private Label label;
	private String labelText;

	private final int IMAGE_SIZE = 164;//缩放后的图片最长的边长为定值。

	/**
	 * 对外使用的构造函数。
	 * @param parent
	 * @param style
	 * @param image
	 * @param labelText
	 */
	public Thumbnails(Composite parent, int style, Image image, String labelText) {
		super(parent, style);
		this.image = image;
		this.labelText = labelText;
		initGUI();
	}

	private void initGUI() {
		GridData data = new GridData ();
		data.widthHint = 170;
		data.heightHint = 180;
		this.setLayoutData(data);
		try {
			GridLayout thisLayout = new GridLayout();
			this.setLayout(thisLayout);

			{
				GridData cLabelImageGridData = new GridData();
				cLabelImageGridData.horizontalAlignment = GridData.FILL;
				cLabelImageGridData.verticalAlignment = GridData.FILL;
				cLabelImageGridData.grabExcessVerticalSpace = true;
				cLabelImageGridData.grabExcessHorizontalSpace = true;
				cLabelImage = new CLabel(this, SWT.NONE);
				cLabelImage.setLayoutData(cLabelImageGridData);

//				cLabelImage.setImage(this.image);
				cLabelImage.addPaintListener(new PaintListener() {
					public void paintControl(PaintEvent evt) {
						cLabelImagePaintControl(evt);
					}
				});
			}
			{
				label = new Label(this, SWT.NONE);
				GridData labelGridData = new GridData();
				labelGridData.horizontalAlignment = GridData.CENTER;
				label.setLayoutData(labelGridData);
				label.setText(this.labelText);
			}
			this.layout();
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

	/**
	 * 缩放图片
	 * @param evt
	 */
	private void cLabelImagePaintControl(PaintEvent evt) {
		Rectangle bounds = image.getBounds();
		int imageWidth = bounds.width;
		int imageHeight = bounds.height;

		int thumbWidth = IMAGE_SIZE;// TODO: 缩放后的图片最大宽度
		int thumbHeight = IMAGE_SIZE;// TODO: 缩放后的图片最大高度

		double ratio = (double)imageWidth/(double)imageHeight;

		//若宽大于高
		if(ratio>(double)1){
			thumbHeight = (int)(thumbWidth/ratio);
		}else {
			thumbWidth = (int)(thumbHeight*ratio);
		}

		// 如果图片小于所略图大小, 不作处理
		if (imageWidth < IMAGE_SIZE && imageHeight < IMAGE_SIZE) {
			thumbWidth = imageWidth;
			thumbHeight = imageHeight;
		}

		evt.gc.drawImage(image, 0, 0, bounds.width, bounds.height, 0, 0,
				thumbWidth, thumbHeight);
		//	 evt.gc.drawImage(image, srcX, srcY, srcWidth, srcHeight, destX, destY, destWidth, destHeight)
	}


	@Override
	public void addMouseListener(MouseListener listener) {
		super.addMouseListener(listener);
		//这样在点击图标或标题的时候，整个控件才能被选中。
		cLabelImage.addMouseListener(listener);
		label.addMouseListener(listener);
	}

	@Override
	public void dispose() {
		if(null !=image && !image.isDisposed()){
			image.dispose();
		}
		if(null !=cLabelImage && !cLabelImage.isDisposed()){
			cLabelImage.dispose();
		}
		if(null !=label && !label.isDisposed()){
			label.dispose();
		}

		super.dispose();
	}
	/**********************************以下代码用于测试SWT控件,实际使用中不会调用*********************************/
	/**
	 * Auto-generated main method to display this
	 * org.eclipse.swt.widgets.Composite inside a new Shell.
	 */
	public static void main(String[] args) {
		showGUI();
	}

	/**
	 * Auto-generated method to display this org.eclipse.swt.widgets.Composite
	 * inside a new Shell.
	 */
	public static void showGUI() {
		Display display = Display.getDefault();
		Shell shell = new Shell(display);

		File imageFile = new File("D:\\sb.jpg");
		Image localImage = null;
		if (imageFile.exists()) {
			ImageDescriptor imageDescriptor = ImageDescriptor.createFromFile(
					null, imageFile.getAbsolutePath());
			localImage = imageDescriptor.createImage();
		}

		Thumbnails inst = new Thumbnails(shell, SWT.NULL, localImage, "hello");

		Point size = inst.getSize();
		shell.setLayout(new FillLayout());
		shell.layout();
		if (size.x == 0 && size.y == 0) {
			inst.pack();
			shell.pack();
		} else {
			Rectangle shellBounds = shell.computeTrim(0, 0, size.x, size.y);
			shell.setSize(shellBounds.width, shellBounds.height);
		}
		shell.open();
		while (!shell.isDisposed()) {
			if (!display.readAndDispatch())
				display.sleep();
		}
	}
}

评论

1 楼 lhlinux 2008-12-06  

编译出错org.eclipse.swt.layout.GridData cannot be cast to org.eclipse.swt.layout.FillData