Awt 简明教程

AWT Layouts

Introduction

布局是指容器中组件的排列方式。换句话说，就是将组件放置在容器内的特定位置。布局管理器会自动完成布局控件的任务。

Layout means the arrangement of components within the container. In other way we can say that placing the components at a particular position within the container. The task of layouting the controls is done automatically by the Layout Manager.

Layout Manager

布局管理器会自动定位容器内的所有控件。即使我们不使用布局管理器，控件也会由默认布局管理器进行定位。可以手动布局控件，但是由于以下两个原因，这样做非常困难。

The layout manager automatically positions all the components within the container. If we do not use layout manager then also the components are positioned by the default layout manager. It is possible to layout the controls by hand but it becomes very difficult because of the following two reasons.

  1. It is very tedious to handle a large number of controls within the container.

  2. Oftenly the width and height information of a component is not given when we need to arrange them.

Java 为我们提供了各种布局管理器来定位控件。各种布局管理器的特性（如大小、形状和布局方式）各不相同。当小程序或应用程序窗口的大小改变时，组件的大小、形状和布局方式也会做出响应相应的改变，即布局管理器适应小程序查看器或应用程序窗口的尺寸。

Java provide us with various layout manager to position the controls. The properties like size,shape and arrangement varies from one layout manager to other layout manager. When the size of the applet or the application window changes the size, shape and arrangement of the components also changes in response i.e. the layout managers adapt to the dimensions of appletviewer or the application window.

布局管理器与容器对象相关联。每个布局管理器都是实现 LayoutManager 接口的类的对象。

The layout manager is associated with every Container object. Each layout manager is an object of the class that implements the LayoutManager interface.

以下是定义布局管理接口功能的接口。

Following are the interfaces defining functionalities of Layout Managers.

Sr. No.

Interface & Description

1

LayoutManager The LayoutManager interface declares those methods which need to be implemented by the class whose object will act as a layout manager.

2

LayoutManager2 The LayoutManager2 is the sub-interface of the LayoutManager.This interface is for those classes that know how to layout containers based on layout constraint object.

AWT Layout Manager Classes:

以下是使用 AWT 设计 GUI 时常用的控件列表。

Following is the list of commonly used controls while designed GUI using AWT.

Sr. No.

LayoutManager & Description

1

BorderLayout The borderlayout arranges the components to fit in the five regions: east, west, north, south and center.

2

CardLayout The CardLayout object treats each component in the container as a card. Only one card is visible at a time.

3

FlowLayout The FlowLayout is the default layout.It layouts the components in a directional flow.

4

GridLayout The GridLayout manages the components in form of a rectangular grid.

5

GridBagLayout This is the most flexible layout manager class.The object of GridBagLayout aligns the component vertically,horizontally or along their baseline without requiring the components of same size.