GridLayout布局

GridLayout 布局的功能非常强大，也是笔者常用的一种布局方式。GridLayout是网格式布局，它把父组件分成一个表格，默认情况下每个子组件占据一个单元格的空间，每个子组件按添加到父组件的顺序排列在表格中。GridLayout提供了很多的属性，可以灵活设置网格的信息。另外，GridLayout 布局提供了GridData类，子组件可以设置相应的GridData，例如 “dogPhoto.setLayoutData(gridData)”，GridData可以设置每个组件当做单元格的信息。

GridLayout的风格

GridLayout类提供了GridLayout 布局中划分网格的信息，主要通过以下几个参数进行设置。

NumColumns：通过“gridLayout.numColumns”属性可以设置父组件中分几列显示子组件。

MakeColumnsEqualWidth：通过“gridLayout. makeColumnsEqualWidth”属性可以设置父组件中子组件是否有相同的列宽，当MakeColumnsEqualWidth为true时表示每列的列宽相等。

MarginLeft：表示当前组件距离父组件左边距的像素点个数。

MarginRight：表示当前组件距离父组件右边距的像素点个数。

MarginTop：表示当前组件距离父组件上边距的像素点个数。

MarginBottom：表示当前组件距离父组件下边距的像素点个数。

HorizontalSpacing：表示子组件的水平间距。

VerticalSpacing：表示子组件的垂直间距。

GridData的相关属性

GridLayout布局的灵活之处在于它利用网格布局数据GridData。通过GridData可以设置子组件在网格中的填充方式、大小边距等信息，用户可以通过子组件的setLayoutData方法设置网格布局数据。

GridData可以控制子组件在网格中的位置大小等相关显示信息。GridData可以设置如下的一些属性。

HorizontalAlignment：表示水平对齐方式。

VerticalAlignment：表示子组件的垂直对齐方式，值和水平方式一样。

HorizontalIndent：表示子组件水平偏移多少像素。此属性和“horizontalAlignment = GridData.BEGINNING”属性一起使用。

HorizontalSpan：表示组件水平占据几个网格。

GrabExcessHorizontalSpace：表示当父组件大小改变时，子组件是否以水平方向抢占空间。

GrabExcessVerticalSpace：表示当父组件大小改变时，子组件是否以垂直方向抢占空间。

WidthHint：表示子组件的宽度为多少像素(前提是未设置其他相关属性)。

HeightHint：表示子组件的高度为多少像素(前提是未设置其他相关属性)。

另外，GridData可以通过构造函数指定相应的属性值，有兴趣的读者可以参考GridData类的构造函数。

测试代码:

GridLayoutSample.java

package swt_jface.demo2;

import org.eclipse.swt.SWT;

import org.eclipse.swt.layout.GridData;

import org.eclipse.swt.layout.GridLayout;

import org.eclipse.swt.widgets.Button;

import org.eclipse.swt.widgets.Display;

import org.eclipse.swt.widgets.List;

import org.eclipse.swt.widgets.Shell;

public class GridLayoutSample {

Display display = new Display();

Shell shell = new Shell(display);

public GridLayoutSample() {

GridLayout gridLayout = new GridLayout();

gridLayout.numColumns = 2;

gridLayout.makeColumnsEqualWidth = true;

shell.setLayout(gridLayout);

Button button1 = new Button(shell, SWT.PUSH);

button1.setText("button1");

button1.setLayoutData(new GridData(GridData.VERTICAL_ALIGN_BEGINNING));

List list = new List(shell, SWT.BORDER);

list.add("item 1");

list.add("item 2");

list.add("item 3");

list.setLayoutData(new GridData(GridData.VERTICAL_ALIGN_CENTER));

Button button2 = new Button(shell, SWT.PUSH);

button2.setText("button #2");

GridData gridData = new GridData(GridData.VERTICAL_ALIGN_END);

gridData.horizontalIndent = 5;

button2.setLayoutData(gridData);

Button button3 = new Button(shell, SWT.PUSH);

button3.setText("3");

button3.setLayoutData(new GridData(GridData.VERTICAL_ALIGN_FILL));

shell.pack();

shell.open();

while (!shell.isDisposed()) {

if (!display.readAndDispatch()) {

display.sleep();

}

}

display.dispose();

}

public static void main(String[] args) {

new GridLayoutSample();

}

}

GridLayoutSampleGrabSpace.java

package swt_jface.demo2;

import org.eclipse.swt.SWT;

import org.eclipse.swt.layout.GridData;

import org.eclipse.swt.layout.GridLayout;

import org.eclipse.swt.widgets.Button;

import org.eclipse.swt.widgets.Display;

import org.eclipse.swt.widgets.Label;

import org.eclipse.swt.widgets.Shell;

import org.eclipse.swt.widgets.Text;

public class GridLayoutSampleGrabSpace {

public GridLayoutSampleGrabSpace() {

Display display = new Display();

Shell shell = new Shell(display);

GridLayout gridLayout = new GridLayout();

gridLayout.numColumns = 3;

shell.setLayout(gridLayout);

Label label = new Label(shell, SWT.BORDER);

label.setText("label");

GridData gridData3 = new GridData();

gridData3.widthHint = 60;

gridData3.heightHint = 20;

label.setLayoutData(gridData3);

Text text = new Text(shell, SWT.SINGLE | SWT.BORDER);

text.setText("text");

GridData gridData = new GridData();

gridData.grabExcessHorizontalSpace = true;

gridData.grabExcessVerticalSpace = true;

gridData.horizontalAlignment = GridData.FILL;

gridData.verticalAlignment = GridData.FILL;

text.setLayoutData(gridData);

Button button = new Button(shell, SWT.PUSH);

button.setText("button");

GridData gridData2 = new GridData();

gridData2.grabExcessVerticalSpace = true;

gridData2.grabExcessHorizontalSpace = true;

gridData2.verticalAlignment = GridData.FILL;

gridData2.horizontalAlignment = GridData.FILL;

button.setLayoutData(gridData2);

shell.setSize(300, 80);

//shell.pack();

shell.open();

while (!shell.isDisposed()) {

if (!display.readAndDispatch()) {

display.sleep();

}

}

display.dispose();

}

public static void main(String[] args) {

new GridLayoutSampleGrabSpace();

}

}

GridLayoutSampleSpan.java

package swt_jface.demo2;

import org.eclipse.swt.SWT;

import org.eclipse.swt.layout.GridData;

import org.eclipse.swt.layout.GridLayout;

import org.eclipse.swt.widgets.Button;

import org.eclipse.swt.widgets.Display;

import org.eclipse.swt.widgets.List;

import org.eclipse.swt.widgets.Shell;

public class GridLayoutSampleSpan {

Display display = new Display();

Shell shell = new Shell(display);

public GridLayoutSampleSpan() {

GridLayout gridLayout = new GridLayout();

gridLayout.numColumns = 2;

gridLayout.makeColumnsEqualWidth = true;

shell.setLayout(gridLayout);

Button button1 = new Button(shell, SWT.PUSH);

button1.setText("button1");

button1.setLayoutData(new GridData(GridData.VERTICAL_ALIGN_BEGINNING));

List list = new List(shell, SWT.BORDER);

list.add("item 1");

list.add("item 2");

list.add("item 3");

list.setLayoutData(new GridData(GridData.VERTICAL_ALIGN_CENTER));

Button button2 = new Button(shell, SWT.PUSH);

button2.setText("button #2");

GridData gridData = new GridData(GridData.VERTICAL_ALIGN_END);

gridData.horizontalSpan = 2;

gridData.horizontalAlignment = GridData.FILL;

button2.setLayoutData(gridData);

Button button3 = new Button(shell, SWT.PUSH);

button3.setText("3");

GridData gridData2 = new GridData(GridData.VERTICAL_ALIGN_END);

gridData2.verticalSpan = 3;

button3.setLayoutData(gridData2);

shell.pack();

shell.open();

while (!shell.isDisposed()) {

if (!display.readAndDispatch()) {

display.sleep();

}

}

display.dispose();

}

public static void main(String[] args) {

new GridLayoutSampleSpan();

}

}

下面这个例子布局稍微复杂一点:

package swt_jface.demo2;

import org.eclipse.swt.SWT;

import org.eclipse.swt.custom.CLabel;

import org.eclipse.swt.graphics.Image;

import org.eclipse.swt.layout.GridData;

import org.eclipse.swt.layout.GridLayout;

import org.eclipse.swt.widgets.Button;

import org.eclipse.swt.widgets.Combo;

import org.eclipse.swt.widgets.Display;

import org.eclipse.swt.widgets.Label;

import org.eclipse.swt.widgets.Shell;

import org.eclipse.swt.widgets.Text;

public class Sample {

Display display = new Display();

Shell shell = new Shell(display);

public Sample() {

shell.setText("Book Entry Demo");

GridLayout gridLayout = new GridLayout(4, false);

gridLayout.verticalSpacing = 8;

shell.setLayout(gridLayout);

Label label = new Label(shell, SWT.NULL);

label.setText("Title: ");

Text title = new Text(shell, SWT.SINGLE | SWT.BORDER);

GridData gridData = new GridData(GridData.HORIZONTAL_ALIGN_FILL);

gridData.horizontalSpan = 3;

title.setLayoutData(gridData);

label = new Label(shell, SWT.NULL);

label.setText("Author(s): ");

Text authors = new Text(shell, SWT.SINGLE | SWT.BORDER);

gridData = new GridData(GridData.HORIZONTAL_ALIGN_FILL);

gridData.horizontalSpan = 3;

authors.setLayoutData(gridData);

label = new Label(shell, SWT.NULL);

label.setText("Cover: ");

gridData = new GridData();

gridData.verticalSpan = 3;

label.setLayoutData(gridData);

CLabel cover = new CLabel(shell, SWT.NULL);

gridData = new GridData(GridData.FILL_HORIZONTAL);

gridData.horizontalSpan = 1;

gridData.verticalSpan = 3;

gridData.heightHint = 100;

gridData.widthHint = 100;

cover.setLayoutData(gridData);

label = new Label(shell, SWT.NULL);

label.setText("Pages");

Text pages = new Text(shell, SWT.SINGLE | SWT.BORDER);

pages.setLayoutData(new GridData(GridData.HORIZONTAL_ALIGN_FILL));

label = new Label(shell, SWT.NULL);

label.setText("Publisher");

Text pubisher = new Text(shell, SWT.SINGLE | SWT.BORDER);

pubisher.setLayoutData(new GridData(GridData.HORIZONTAL_ALIGN_FILL));

label = new Label(shell, SWT.NULL);

label.setText("Rating");

Combo rating = new Combo(shell, SWT.READ_ONLY);

rating.setLayoutData(new GridData(GridData.HORIZONTAL_ALIGN_FILL));

rating.add("5");

rating.add("4");

rating.add("3");

rating.add("2");

rating.add("1");

label = new Label(shell, SWT.NULL);

label.setText("Abstract:");

Text bookAbstract =

new Text(

shell,

SWT.WRAP

| SWT.MULTI

| SWT.BORDER

| SWT.H_SCROLL

| SWT.V_SCROLL);

gridData =

new GridData(

GridData.HORIZONTAL_ALIGN_FILL | GridData.VERTICAL_ALIGN_FILL);

gridData.horizontalSpan = 3;

gridData.grabExcessVerticalSpace = true;

bookAbstract.setLayoutData(gridData);

Button enter = new Button(shell, SWT.PUSH);

enter.setText("Enter");

gridData = new GridData();

gridData.horizontalSpan = 4;

gridData.horizontalAlignment = GridData.END;

enter.setLayoutData(gridData);

title.setText("Professional Java Interfaces with SWT/JFace");

authors.setText("Jack Li Guojie");

pages.setText("500pp");

pubisher.setText("John Wiley & Sons");

cover.setBackground(new Image(display, "C:/eclipse32.gif"));

bookAbstract.setText(

"This book provides a comprehensive guide for \n"

+ "you to create Java user interfaces with SWT/JFace. ");

shell.pack();

shell.open();

while (!shell.isDisposed()) {

if (!display.readAndDispatch()) {

display.sleep();

}

}

display.dispose();

}

public static void main(String[] args) {

new Sample();

}

}

GridLayout 布局的功能非常强大，也是笔者常用的一种布局方式。GridLayout是网格式布局，它把父组件分成一个表格，默认情况下每个子组件占据一个单元格的空间，每个子组件按添加到父组件的顺序排列在表格中。

GridLayout提供了很多的属性，可以灵活设置网格的信息。另外，GridLayout 布局提供了GridData类，子组件可以设置相应的GridData，例如“dogPhoto.setLayoutData(gridData)”，GridData可以设置每个组件当做单元格的信息。

14.11.1 GridLayout的风格

GridLayout类提供了GridLayout 布局中划分网格的信息，主要通过以下几个参数进行设置。

NumColumns：通过“gridLayout.numColumns”属性可以设置父组件中分几列显示子组件，如表14-4所示。

表14-4  NumColumns效果

列    数

显 示 效 果

numColumns = 1

numColumns = 2

numColumns = 3

MakeColumnsEqualWidth：通过“gridLayout. makeColumnsEqualWidth”属性可以设置父组件中子组件是否有相同的列宽，当MakeColumnsEqualWidth为true时表示每列的列宽相等。

MarginLeft：表示当前组件距离父组件左边距的像素点个数。

MarginRight：表示当前组件距离父组件右边距的像素点个数。

MarginTop：表示当前组件距离父组件上边距的像素点个数。

MarginBottom：表示当前组件距离父组件下边距的像素点个数。

HorizontalSpacing：表示子组件的水平间距。

VerticalSpacing：表示子组件的垂直间距。