java布局之GridBagLayout

GridBagLayout类似GridLayout但是比它更加灵活,更加复杂,因为它的每个单元的 宽度和高度的值是可以不相等的。GridBagLayout是利用GridBagLayoutConstraints的约束条件来对组件进行约束添加。关于这个GridBagLayoutConstraints有几个重要的参数,我们只要理解了这个,剩下的就好办了。

1:gridx,gridy:

这个表示的组件的横向索引和纵向索引,int类型,索引指向的值就是对应的单元格。

2:gridwidth,gridheight

这个表示的是一个组件占据的单元格的数目,int类型。首先,占据的数目大不意味着组件大,因为它周边可能是空白。其次,要注意的是,这里gridwidth,gridheight的值可以超过行最大组件数,列最大组件数,但是超过之后也没意义,超过之后系统会把它变成行或者列的最大值。例如GridBagLayout是M×N格子,那么Gridwidth最大有效值就是M,gridheight的最大有效值就是N。

默认值是1。

3:weightx,weighty

指定如何分布额外的水平,竖直空间。这个意思也很简单,权重越大,在窗口面积发生变化时,组件周围占据的空白就越大,就好比膨胀一样,原本组件1原本占据的单元格比组件2大,那么在膨胀后,它占据的空白就比组件2更多。

默认值是0

4:fill

这个指定怎么填充组件占据的空白,有HORIZENTAL,VERTICAL,BOTH,NULL。

默认值是NULL

5:anchor

这个主要是规定组件在它显示区域内应该以何种方式显示,说白了就是各种对齐的问题。

6:insets

这个是一个Inset类,指定组件与其上,左,底,右之间的距离,单位是像素,不是单元格。默认值是(0,0,0,0)

Insets(int top,int left,int bottom,int right)

7:ipadx,ipady

指定组件内部的宽,高,组件的大小等于组件的最小宽,高加上对应的ipadx,ipady。

默认值都是0.

/*
 * GirdBagLayoutDemo.java requires no other files.
 */
 

import java.awt.Container;

import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;


import javax.swing.JButton;
import javax.swing.JFrame;

 
public class GridBagLayouts extends JFrame{
	
	private JButton btn1 = new JButton("Button1");
	private JButton btn2 = new JButton("Button2");
	private JButton btn3 = new JButton("Button3 what a fine day");
	private JButton btn4 = new JButton("Button4 what a fine da");
	private JButton btn5 = new JButton("Button5 what a fine d");
	private JButton btn6 = new JButton("Button6 what a fines");
	
	GridBagLayouts()
	{
		super();
		initComponent();
		
	}
	private void initComponent()
	{
		Container container = this.getContentPane();
		container.setLayout(new GridBagLayout());
		GridBagConstraints ctr1 = new GridBagConstraints();
		ctr1.gridx = 0;
		ctr1.gridy = 0;
		ctr1.weighty = 3;
		//ctr1.weightx = 1;
		ctr1.gridwidth = 4;
		ctr1.gridheight = 1;
		//ctr1.anchor = GridBagConstraints.WEST;
		ctr1.fill = GridBagConstraints.HORIZONTAL;
		container.add(btn1,ctr1);
		
		GridBagConstraints ctr2 = new GridBagConstraints();
		ctr2.gridx = 0;
		ctr2.gridy = 1;
		ctr2.weighty = 2;
		//ctr2.weightx = 2;
		ctr2.gridwidth = 2;
		ctr2.gridheight = 1;
		//ctr2.anchor = GridBagConstraints.WEST;
		ctr2.fill = GridBagConstraints.HORIZONTAL;
		container.add(btn2,ctr2);
		
		GridBagConstraints ctr3 = new GridBagConstraints();
		ctr3.gridx= 2;
		ctr3.gridy = 1;
		ctr3.weighty = 2;
		//ctr3.weightx = 1;
		ctr3.gridwidth = 1;
		ctr3.gridheight = 1;
		//ctr3.anchor = GridBagConstraints.WEST;
		ctr3.fill = GridBagConstraints.HORIZONTAL;
		ctr3.insets = new Insets(0,20,0,0);//top,left,bottom,right
		ctr3.ipady = 40;
		container.add(btn3,ctr3);
		
		GridBagConstraints ctr4 = new GridBagConstraints();
		ctr4.gridx = 0;
		ctr4.gridy = 2;
		ctr4.weighty = 1;
		//ctr4.weightx = 3;
		ctr4.gridwidth = 1;
		ctr4.gridheight = 1;
		//ctr4.anchor = GridBagConstraints.WEST;
		ctr4.fill = GridBagConstraints.HORIZONTAL;
		container.add(btn4,ctr4);
		
		GridBagConstraints ctr5 = new GridBagConstraints();
		ctr5.gridx = 1;
		ctr5.gridy = 2;
		ctr5.weighty = 1;
		//ctr5.weightx = 2;
		ctr5.gridwidth = 1;
		ctr5.gridheight = 1;
		//ctr5.anchor = GridBagConstraints.WEST;
		ctr5.fill = GridBagConstraints.HORIZONTAL;
		container.add(btn5,ctr5);
		
		GridBagConstraints ctr6 = new GridBagConstraints();
		ctr6.gridx = 2;
		ctr6.gridy = 2;
		ctr6.weighty = 1;
		//ctr6.weightx = 1;
		ctr6.gridwidth = 2;
		ctr6.gridheight = 1;
		ctr6.fill = GridBagConstraints.HORIZONTAL;
		container.add(btn6,ctr6);
	}
	
	public static void main(String[] args)
	{
		GridBagLayouts frame = new GridBagLayouts();
		frame.pack();
		frame.setVisible(true);
	}
	
}

程序运行结果:

java布局之GridBagLayout_第1张图片

从图中可以看出

1:对于这样的网格Layout,我们可以忽略一些网格组件的设置,并不是每个网格都必须有组件

2:对于权重来说,有纵向比较,横向比较。在比较时,根据这一列(行)不同组件权重的对应大小,然后在窗口扩张中按照对应的权重来增加间距。如上图,button1的纵向权重最大,那么窗口变大时,它周围的空白就越多。

3:inset单位是像素,表示的是组件之间的间距

4:ipadx,ipady表示的 是组件内部的距离。



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