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Eclipse开发经典教程:SWT布局

GridLayout 布局实例

为了更深入地理解GridLayout 布局,下面通过具体的实例演示如何构建一个比较复杂的布局窗口。通过本例的学习,读者可以比较好地掌握GridLayout布局,代码如例程3所示。

例程3 ComplexGridLayoutExample.java
public class ComplexGridLayoutExample { static Display display; static Shell shell; static Text dogName; static Combo dogBreed; static Canvas dogPhoto; static Image dogImage; static List categories; static Text ownerName; static Text ownerPhone; public static void main(String[] args) { display = new Display(); shell = new Shell(display); shell.setText("Dog Show Entry"); //新建GridLayout布局 GridLayout gridLayout = new GridLayout(); //把子组件分成3列显示 gridLayout.numColumns = 3; shell.setLayout(gridLayout); new Label(shell, SWT.NONE).setText("Dog's Name:"); dogName = new Text(shell, SWT.SINGLE | SWT.BORDER); //新建水平填充的GridData GridData gridData = new GridData(GridData.HORIZONTAL_ALIGN_FILL); //GridData的组件占两列显示 gridData.horizontalSpan = 2; dogName.setLayoutData(gridData); new Label(shell, SWT.NONE).setText("Breed:"); dogBreed = new Combo(shell, SWT.NONE); dogBreed.setItems(new String [] {"Collie", "Pitbull", "Poodle", "Scottie"}); dogBreed.setLayoutData(new GridData(GridData.HORIZONTAL_ALIGN_FILL)); Label label = new Label(shell, SWT.NONE); label.setText("Categories"); label.setLayoutData(new GridData(GridData.HORIZONTAL_ALIGN_CENTER)); new Label(shell, SWT.NONE).setText("Photo:"); dogPhoto = new Canvas(shell, SWT.BORDER); //gridData两端填充 gridData = new GridData(GridData.FILL_BOTH); //gridData非常好的宽度和高度 gridData.widthHint = 80; gridData.heightHint = 80; //设置gridData的子组件垂直占3行 gridData.verticalSpan = 3; dogPhoto.setLayoutData(gridData); //添加画布的重画事件 dogPhoto.addPaintListener(new PaintListener() { public void paintControl(final PaintEvent event) { if (dogImage != null) { event.gc.drawImage(dogImage, 0, 0); } } }); categories = new List(shell, SWT.MULTI | SWT.BORDER | SWT.V_SCROLL); categories.setItems(new String [] { "Best of Breed", "Prettiest Female", "Handsomest Male", "Best Dressed", "Fluffiest Ears", "Most Colors", "Best Performer", "Loudest Bark", "Best Behaved", "Prettiest Eyes", "Most Hair", "Longest Tail", "Cutest Trick"}); gridData = new GridData(GridData.HORIZONTAL_ALIGN_FILL | GridData. VERTICAL_ALIGN_FILL); gridData.verticalSpan = 4; int listHeight = categories.getItemHeight() * 12; Rectangle trim = categories.computeTrim(0, 0, 0, listHeight); gridData.heightHint = trim.height; categories.setLayoutData(gridData); Button browse = new Button(shell, SWT.PUSH); browse.setText("Browse..."); gridData = new GridData(GridData.HORIZONTAL_ALIGN_FILL); gridData.horizontalIndent = 5; browse.setLayoutData(gridData); //添加按钮的选择事件 browse.addSelectionListener(new SelectionAdapter() { public void widgetSelected(SelectionEvent event) { String fileName = new FileDialog(shell).open(); if (fileName != null) { dogImage = new Image(display, fileName); dogPhoto.redraw(); } } }); Button delete = new Button(shell, SWT.PUSH); delete.setText("Delete"); gridData = new GridData(GridData.HORIZONTAL_ALIGN_FILL | GridData. VERTICAL_ALIGN_BEGINNING); gridData.horizontalIndent = 5; delete.setLayoutData(gridData); delete.addSelectionListener(new SelectionAdapter() { public void widgetSelected(SelectionEvent event) { if (dogImage != null) { dogImage.dispose(); dogImage = null; dogPhoto.redraw(); } } }); Group ownerInfo = new Group(shell, SWT.NONE); ownerInfo.setText("Owner Info"); gridLayout = new GridLayout(); gridLayout.numColumns = 2; ownerInfo.setLayout(gridLayout); gridData = new GridData(GridData.HORIZONTAL_ALIGN_FILL); gridData.horizontalSpan = 2; ownerInfo.setLayoutData(gridData); new Label(ownerInfo, SWT.NONE).setText("Name:"); ownerName = new Text(ownerInfo, SWT.SINGLE | SWT.BORDER); ownerName.setLayoutData(new GridData(GridData.FILL_HORIZONTAL)); new Label(ownerInfo, SWT.NONE).setText("Phone:"); ownerPhone = new Text(ownerInfo, SWT.SINGLE | SWT.BORDER); ownerPhone.setLayoutData(new GridData(GridData.FILL_HORIZONTAL)); Button enter = new Button(shell, SWT.PUSH); enter.setText("Enter"); gridData = new GridData(GridData.HORIZONTAL_ALIGN_END); gridData.horizontalSpan = 3; enter.setLayoutData(gridData); enter.addSelectionListener(new SelectionAdapter() { public void widgetSelected(SelectionEvent event) { System.out.println("\nDog Name: " + dogName.getText()); System.out.println("Dog Breed: " + dogBreed.getText()); System.out.println("Owner Name: " + ownerName.getText()); System.out.println("Owner Phone: " + ownerPhone.getText()); System.out.println("Categories:"); String cats[] = categories.getSelection(); for (int i = 0; i < cats.length; i++) { System.out.println("\t" + cats[i]); } } }); shell.pack(); shell.open(); while (!shell.isDisposed()) { if (!display.readAndDispatch()) display.sleep(); } if (dogImage != null) { dogImage.dispose(); } } }

程序中构建了一个比较复杂的窗口,设置了GridLayout的布局信息和相关的GridData网格数据信息,程序运行效果如图5所示。


图5 GridLayout布局实例


注意:每个GridData都必须有单独的实例,几个子组件不能够共用同一个GridData(即使几个组件有相同属性的GridData也必须新建几个实例)。

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