TweetFollow Us on Twitter

Java Grids
Volume Number:12
Issue Number:11
Column Tag:Getting Started

Two Java Grid Layouts

By Dave Mark

Note: Source code files accompanying article are located on MacTech CD-ROM or source code disks.

Last month, we introduced the Java Layout Manager and saw the power of layouts combined with panels. This month, we’ll look at two important layout classes, GridLayout and GridBagLayout, and present a series of applets that bring these two classes to life.

There is a newly reformatted set of Java API documentation, collectively known as the 1.0.2 API. If you don’t already have this, go get it now. The URL is:

http://java.sun.com/doc/api_documentation.html

There are two Mac download links on this page. Though it’s bigger, you might try the .hqx file (as opposed to the .bin file). I’m not sure why, but when I downloaded the .bin file and dropped it on StuffIt Expander, the final .sea file was corrupted. On the other hand, by the time you read this, the problem most likely will have been corrected.

GridLayout

As its name implies, the GridLayout lays out its components in a grid. GridLayout has two constructors:

public GridLayout( int  rows, int  cols );

This one creates a grid layout with the specified rows and columns. As you’ll see, GridLayout does the best it can to lay the current set of components out in this configuration. But what if you have too few components? Or too many? This month’s sample applets are ideal for experimenting.

The second constructor adds two new parameters:

public GridLayout( int  rows, int  cols,
                   int  hgap, int  vgap );

This version creates a grid layout with the specified rows and columns, but also lets you specify a minimal horizontal and vertical gap to appear between the components.

GridLayout is pretty straightforward. Here’s a sample applet to take it for a spin.

• Launch the CodeWarrior IDE and create a new “Java Applet” project called GridLayout.µ.

• Create a new source code window, type in the following source code, save as GridLayout.Java, and add to it the project.

import java.awt.*;

public class MyGrid extends java.applet.Applet
{
 public MyGrid()
 {
 setLayout( new GridLayout( 4, 4 ) );
 
 add( new Button( “1” ) );
 add( new Button( “2” ) );
 add( new Button( “3” ) );
 add( new Button( “4” ) );
 add( new Button( “5” ) );
 add( new Button( “6” ) );
 add( new Button( “7” ) );
 add( new Button( “8” ) );
 add( new Button( “9” ) );
 add( new Button( “10” ) );
 add( new Button( “11” ) );
 add( new Button( “12” ) );
 add( new Button( “13” ) );
 add( new Button( “14” ) );
 add( new Button( “15” ) );
 add( new Button( “16” ) );
 }
}

• Create a second source code window, type in the following HTML, save as GridLayout.html, and add it to the project as well.

<title>GridLayout</title>
<hr>
<applet codebase=”GridLayout Files” code=”MyGrid.class” width=200 height=200>
</applet>
<hr>
<a href=”GridLayout.java”>The source.</a>

• Remove the two <replace me> files from the project (Apple-click on the files to select them, then hit option-delete).

• Edit the project prefs, specifically, the Java Project pane. Set the Project Type popup to “Class Folder” and type “GridLayout Files” (without the quotes) as the Folder Name.

It’s important that the Class Folder preference exactly match the “codebase” attribute in your HTML file.

• Once all your source is in place, select Make from the Project menu to generate your class file.

• To run your applet, drop the html file onto your Java Applet runner or Java-capable browser. Figure 1 shows my version running in a Netscape window.

Figure 1. The GridLayout applet, running in Netscape.

The GridLayout Source Code

Here’s how the source code works. First comes the normal opening stuff, the import statement and class definition. The setLayout() statement creates a new GridLayout object with 4 rows and 4 columns, and makes it the current layout.

import java.awt.*;

public class MyGrid extends java.applet.Applet
{
 public MyGrid()
 {
 setLayout( new GridLayout( 4, 4 ) );

Next, we create a series of 16 buttons and add them to the current frame.

 add( new Button( “1” ) );
 add( new Button( “2” ) );
 add( new Button( “3” ) );
 add( new Button( “4” ) );
 add( new Button( “5” ) );
 add( new Button( “6” ) );
 add( new Button( “7” ) );
 add( new Button( “8” ) );
 add( new Button( “9” ) );
 add( new Button( “10” ) );
 add( new Button( “11” ) );
 add( new Button( “12” ) );
 add( new Button( “13” ) );
 add( new Button( “14” ) );
 add( new Button( “15” ) );
 add( new Button( “16” ) );
 }
}

That’s it! When you run the applet, your 16 buttons will appear in a 4 by 4 grid. The width and height of the buttons is determined by the width and height attributes in your HTML’s applet tag. Make the applet frame wider, the buttons will each be made wider. Make the frame taller, the buttons will each be made taller.

You can also affect the results by changing the parameters you pass to the GridLayout constructor. Experiment.

GridLayout, Version 2

Here’s another GridLayout applet. This one uses all four constructor parameters, and includes a nifty little trick you’ll want to remember. First, here’s the code:

import java.awt.*;

public class MyGrid extends java.applet.Applet
{
 int    numButtons;
 String att;
 
 public void init()
 {
 att = getParameter( “NUMBUTTONS” );
 numButtons = Integer.valueOf(att).intValue();
 
 setLayout( new GridLayout( 2, 20, 5, 20 ) );
 
 for ( int i=1; i<=numButtons; i++ )
 add( new Button( “”+i ) );
 }
}

Next, here’s the HTML:

<title>GridLayout</title>
<hr>
<applet codebase=”GridLayout Files” code=”MyGrid.class” width=400 height=200>
<param name=”NUMBUTTONS” value=”16”>
</applet>
<hr>
<a href=”GridLayout.java”>The source.</a>

Figure 2 shows the applet in action, running under Netscape. Let’s take a look at this source.

Figure 2. Another GridLayout applet using all 4 parameters.

GridLayout 2 Source Code

This version of GridLayout.Java starts off in the same way, but does its creating in init() instead of in MyGrid(). This gives us access to the HTML parameters. I’m not sure why getParameter() doesn’t work from within MyGrid(), but I’ll look into it.

import java.awt.*;

public class MyGrid extends java.applet.Applet
{
 int    numButtons;
 String att;

If you look back at the HTML, you’ll see that we stuck in a parameter with the name “NUMBUTTONS” and a value of “16”. We call getParameter() to pick up the parameter and Integer.valueOf(att).intValue() to convert the returned string to a number. Next, we create a new GridLayout using all 4 parameters and make it the current layout. Note that we’ve specified 2 rows and 20 columns, with 5 pixels horizontally and 20 pixels vertically between components. The Layout Manager uses the row value first for GridLayouts, so the fact that you’ve specified 20 columns really has no affect. Try using 0 for a column value.

 public void init()
 {
 att = getParameter( “NUMBUTTONS” );
 numButtons = Integer.valueOf(att).intValue();
 
 setLayout( new GridLayout( 2, 20, 5, 20 ) );

Now for the cool trick. In our earlier example, we explicitly specified the name of each button using Strings like “1”, “2”, etc. In this case, we add the loop counter, i, to the null string to produce a string representation of the loop counter. Basically, we’ve forced Java to do the typecasting from number to String for us, since the + operator is expecting a String on both sides. Pretty cool, eh?

 for ( int i=1; i<=numButtons; i++ )
 add( new Button( “”+i ) );
 }
}

The GridBagLayout

The GridLayout works pretty well if all your components are the same size. But, suppose you are working with all sorts of elements; some tall, some wide, whatever. In this case, the GridLayout won’t work particularly well (it’ll waste a lot of screen real estate). Fortunately, there is a complex, grid-based class designed to handle variable sized components.

GridBagLayout and its sister class, GridBagConstraints, allow you to customize a layout that allows components to span multiple grid cells. The GridBagConstraints class features a number of variables, each designed to constrain any components added to the current GridBagLayout. Take a look at the GridBagConstraints class declaration:

public  class  Java.awt.GridBagConstraints
    extends  Java.lang.Object
    implements Java.lang.Cloneable
{
        // Fields
    public int anchor;
    public int fill;
    public int gridheight;
    public int gridwidth;
    public int gridx;
    public int gridy;
    public Insets insets;
    public int ipadx;
    public int ipady;
    public double weightx;
    public double weighty;

        // the anchor field has one of the following values     
    public final static int CENTER;
    public final static int EAST;
    public final static int NORTH;
    public final static int NORTHEAST;
    public final static int NORTHWEST;
    public final static int SOUTH;
    public final static int SOUTHEAST;
    public final static int SOUTHWEST;
    public final static int WEST;

        // the fill field has one of the following values       
    public final static int BOTH;
    public final static int HORIZONTAL;
    public final static int NONE;
    public final static int VERTICAL;

        // default value for gridheight, gridwidth
    public final static int REMAINDER;

        // default value for gridx, gridy
    public final static int RELATIVE;

        // Constructors
    public GridBagConstraints();

        // Methods
    public Object clone();
}

To use a GridBagLayout, you’ll create a GridBagLayout object along with a corresponding GridBagConstraints object, then make the GridBagLayout the current object. Next, you’ll set your GridBagConstraints fields to the settings you prefer. Now you are ready to start adding components to the current frame. All the added components will be formatted according to the current GridBagConstraints settings. Change the constraints settings and add some more components. The changed constraints only affect future components, not the components that were already added.

anchor determines where, within a cell, the component is placed. fill determines if the component is reissued to fill its cell and, if so, how. gridheight specifies the number of cells in a column. gridwidth specifies the number of cells in a row. REMAINDER is used to mark a component as the last in its row or column. RELATIVE is used to mark a component as next to last.

gridx and gridy allow you to specify where to place the component in the grid. A value of (0,0) will put the next component in the upper left corner. A value of RELATIVE will put the component either at the end of a row (in the case of gridx) or column (in the case of gridy).

insets specifies the number of pixels of padding on any side of a cell. ipadx and ipady allow you to specify the padding in pixels within a cell.

Finally, weightx and weighty allow you to specify how much horizontal and vertical space this component should consume when the available extra display area is divvied up between all the components in a row or column.

A GridBagLayout Example

There is really no way to truly appreciate the GridBagLayout without playing with an example. The following is one of the standard Sun applets, stripped down to make it as small as possible. Take some time to play with this applet. Change the constraints, experiment with all the fields and settings to see what they do.

Here’s the source code:

import java.awt.*;

public class MyGridBag extends java.applet.Applet
{
 public MyGridBag()
 {
 GridBagLayout   gridBag = new GridBagLayout();
 GridBagConstraintsconstraints =
                new GridBagConstraints();
 
 setLayout( gridBag );
 
 constraints.fill  =  constraints.BOTH;
 constraints.weightx  =  1.0;

 ConstrainedButton(“Button1”,  gridBag,  constraints );
 ConstrainedButton(“Button2”,  gridBag,  constraints );
 ConstrainedButton(“Button3”,  gridBag,  constraints );

 constraints.gridwidth  =  constraints.REMAINDER;  

 ConstrainedButton(“Button4”,  gridBag,  constraints );

 constraints.weightx  =  0.0;

 ConstrainedButton(“Button5”,  gridBag,  constraints );
 
 constraints.gridwidth  =  constraints.RELATIVE;
 
 ConstrainedButton(“Button6”,  gridBag,  constraints );
 
 constraints.gridwidth  =  constraints.REMAINDER;
 
 ConstrainedButton(“Button7”,  gridBag,  constraints );
 
 constraints.gridwidth  =  1;
 constraints.gridheight  =  2;
 constraints.weighty  =  1.0;
 
 ConstrainedButton(“Button8”,  gridBag,  constraints );
 
 constraints.weighty  =  0.0;
 constraints.gridwidth  =  constraints.REMAINDER;  
 constraints.gridheight  =  1;
 
 ConstrainedButton(“Button9”,  gridBag,  constraints );
 ConstrainedButton(“Button10”,  gridBag,  constraints );
 }
 
 void ConstrainedButton( String title,
 GridBagLayout layout, GridBagConstraints constraints )
 {
 Button button = new Button( title );
 layout.setConstraints( button, constraints );
 add( button );
 }
}

Here’s the HTML:

<title>GridBagLayout</title>
<hr>
<applet codebase=”GridBagLayout Files” code=”MyGridBag.class” width=400 
height=100>
</applet>
<hr>
<a href=”GridBagLayout.java”>The source.</a>

Figure 3 shows the results of this applet, when run in Netscape.

Figure 3. The classic GridBagLayout applet from Sun.

Till Next Month...

As you go through the GridBagLayout source, pay attention to the use of REMAINDER and RELATIVE. Remember, you are marking a component as 2nd to last and last in its row or column. For example, Button4 should be the last in its row. Button6 should be RELATIVE (2nd to last) while Button7 should be REMAINDER (last). All the buttons should use a gridheight of 1 except for Button8, which will use a gridheight of 2. You get the idea.

Next month, we’ll take a look at double-buffered animation, something that Java makes fairly easy to do. Till then, have a Happy Thanksgiving and save me a wishbone...

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Duplicate Annihilator 5.7.5 - Find and d...
Duplicate Annihilator takes on the time-consuming task of comparing the images in your iPhoto library using effective algorithms to make sure that no duplicate escapes. Duplicate Annihilator... Read more
BusyContacts 1.0.2 - Fast, efficient con...
BusyContacts is a contact manager for OS X that makes creating, finding, and managing contacts faster and more efficient. It brings to contact management the same power, flexibility, and sharing... Read more
Capture One Pro 8.2.0.82 - RAW workflow...
Capture One Pro 8 is a professional RAW converter offering you ultimate image quality with accurate colors and incredible detail from more than 300 high-end cameras -- straight out of the box. It... Read more
Backblaze 4.0.0.872 - Online backup serv...
Backblaze is an online backup service designed from the ground-up for the Mac.With unlimited storage available for $5 per month, as well as a free 15-day trial, peace of mind is within reach with... Read more
Little Snitch 3.5.2 - Alerts you about o...
Little Snitch gives you control over your private outgoing data. Track background activity As soon as your computer connects to the Internet, applications often have permission to send any... Read more
Monolingual 1.6.4 - Remove unwanted OS X...
Monolingual is a program for removing unnecesary language resources from OS X, in order to reclaim several hundred megabytes of disk space. If you use your computer in only one (human) language, you... Read more
CleanApp 5.0 - Application deinstaller a...
CleanApp is an application deinstaller and archiver.... Your hard drive gets fuller day by day, but do you know why? CleanApp 5 provides you with insights how to reclaim disk space. There are... Read more
Fantastical 2.0 - Create calendar events...
Fantastical is the Mac calendar you'll actually enjoy using. Creating an event with Fantastical is quick, easy, and fun: Open Fantastical with a single click or keystroke Type in your event details... Read more
Cocktail 8.2 - General maintenance and o...
Cocktail is a general purpose utility for OS X that lets you clean, repair and optimize your Mac. It is a powerful digital toolset that helps hundreds of thousands of Mac users around the world get... Read more
Direct Mail 4.0.4 - Create and send grea...
Direct Mail is an easy-to-use, fully-featured email marketing app purpose-built for OS X. It lets you create and send great looking email campaigns. Start your newsletter by selecting from a gallery... Read more

Fast & Furious: Legacy's Creati...
| Read more »
N-Fusion and 505's Ember is Totally...
| Read more »
These are All the Apple Watch Apps and G...
The Apple Watch is less than a month from hitting store shelves, and once you get your hands on it you're probably going to want some apps and games to install. Fear not! We've compiled a list of all the Apple Watch apps and games we've been able to... | Read more »
Appy to Have Known You - Lee Hamlet Look...
Being at 148Apps these past 2 years has been an awesome experience that has taught me a great deal, and working with such a great team has been a privilege. Thank you to Rob Rich, and to both Rob LeFebvre and Jeff Scott before him, for helping me... | Read more »
Hands-On With Allstar Heroes - A Promisi...
Let’s get this out of the way quickly. Allstar Heroes looks a lot like a certain other recent action RPG release, but it turns out that while it’s not yet available here, Allstar Heroes has been around for much longer than that other title. Now that... | Read more »
Macho Man and Steve Austin Join the Rank...
WWE Immortals, by Warner Bros. Interactive Entertainment and WWE, has gotten a superstar update. You'll now have access to Macho Man Randy Savage and Steve Austin. Both characters have two different versions: Macho Man Randy Savage Renegade or Macho... | Read more »
Fearless Fantasy is Fantastic for the iF...
I actually had my first look at Fearless Fantasy last year at E3, but it was on a PC so there wasn't much for me to talk about. But now that I've been able to play with a pre-release version of the iOS build, there's quite a bit for me to talk... | Read more »
MLB Manager 2015 (Games)
MLB Manager 2015 5.0.14 Device: iOS Universal Category: Games Price: $4.99, Version: 5.0.14 (iTunes) Description: Guide your favorite MLB franchise to glory! MLB Manager 2015, officially licensed by MLB.com and based on the award-... | Read more »
Breath of Light (Games)
Breath of Light 1.0.1421 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0.1421 (iTunes) Description: Hold a quiet moment. Breath of Light is a meditative and beautiful puzzle game with a hypnotic soundtrack by... | Read more »
WWE WrestleMania Tags into the App Store
Are You ready to rumble? The official WWE WrestleMania app, by World Wrestling Entertainment, is now available. Now you can get all your WrestleMania info in one place before anyone else. The app offers details on superstar signings, interactive... | Read more »

Price Scanner via MacPrices.net

Samsung Galaxy S 6 and Galaxy S 6 edge U.S. P...
Samsung Electronics America, Inc. has announced the Galaxy S 6 and Galaxy S 6 edge will be available in the U.S. beginning April 10, with pre-orders being accepted now. “We have completely reimagined... Read more
13-inch 2.5GHz MacBook Pro (refurbished) avai...
The Apple Store has Apple Certified Refurbished 13″ 2.5GHz MacBook Pros available for $829, or $270 off the cost of new models. Apple’s one-year warranty is standard, and shipping is free: - 13″ 2.... Read more
Save up to $80 on iPad Air 2s, NY tax only, f...
 B&H Photo has iPad Air 2s on sale for $80 off MSRP including free shipping plus NY sales tax only: - 16GB iPad Air 2 WiFi: $469.99 $30 off - 64GB iPad Air 2 WiFi: $549.99 $50 off - 128GB iPad... Read more
iMacs on sale for up to $205 off MSRP
B&H Photo has 21″ and 27″ iMacs on sale for up to $205 off MSRP including free shipping plus NY sales tax only: - 21″ 1.4GHz iMac: $1019 $80 off - 21″ 2.7GHz iMac: $1189 $110 off - 21″ 2.9GHz... Read more
Färbe Technik Offers iPhone Battery Charge LI...
Färbe Technik, which manufactures and markets of mobile accessories for Apple, Blackberry and Samsung mobile devices, is offering tips on how to keep your iPhone charged while in the field: •... Read more
Electronic Recyclers International CEO Urges...
Citing a recent story on CNBC about concerns some security professionals have about the forthcoming Apple Watch, John Shegerian, Chairman and CEO of Electronic Recyclers International (ERI), the... Read more
Save up to $380 with Apple refurbished iMacs
The Apple Store has Apple Certified Refurbished iMacs available for up to $380 off the cost of new models. Apple’s one-year warranty is standard, and shipping is free: - 27″ 3.5GHz 5K iMac – $2119 $... Read more
Mac minis on sale for up to $75 off, starting...
MacMall has Mac minis on sale for up to $75 off MSRP including free shipping. Their prices are the lowest available for these models from any reseller: - 1.4GHz Mac mini: $459.99 $40 off - 2.6GHz Mac... Read more
College Student Deals: Additional $50 off Mac...
Take an additional $50 off all MacBooks and iMacs at Best Buy Online with their College Students Deals Savings, valid through April 11, 2015. Anyone with a valid .EDU email address can take advantage... Read more
Mac Pros on sale for up to $260 off MSRP
B&H Photo has Mac Pros on sale for up to $260 off MSRP. Shipping is free, and B&H charges sales tax in NY only: - 3.7GHz 4-core Mac Pro: $2799, $200 off MSRP - 3.5GHz 6-core Mac Pro: $3719.99... Read more

Jobs Board

DevOps Software Engineer - *Apple* Pay, iOS...
**Job Summary** Imagine what you could do here. At Apple , great ideas have a way of becoming great products, services, and customer experiences very quickly. Bring Read more
*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
Sr. Technical Services Consultant, *Apple*...
**Job Summary** Apple Professional Services (APS) has an opening for a senior technical position that contributes to Apple 's efforts for strategic and transactional Read more
Lead *Apple* Solutions Consultant - Retail...
**Job Summary** Job Summary The Lead ASC is an Apple employee who serves as the Apple business manager and influencer in a hyper-business critical Reseller's store Read more
*Apple* Pay - Site Reliability Engineer - Ap...
**Job Summary** Imagine what you could do here. At Apple , great ideas have a way of becoming great products, services, and customer experiences very quickly. Bring Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.