Chat Transcript, June 6, 8:30pm
For this chat session, we are referring to several web pages that do not show up in this transcript. Sorry ...
=> [wachsmut] joins at Fri Jun 06 20:27:30 1997 from 153.35.6.46
=> [Don] joins at Fri Jun 06 20:28:13 1997 from 206.173.45.39
 | wachsmut=> Hi Don, what's up ... |
| Don=> not too much, how about you? |
| wachsmut=> waiting for more people to arrive ! |
=> [Jenn] joins at Fri Jun 06 20:29:28 1997 from 199.174.141.49
| Don=> yeah, but its a nice nite so probably outside |
| Don=> or watching basketball maybe??!! |
| wachsmut=> Right ... |
| wachsmut=> Hi Jenn .... |
=> [Rob] joins at Fri Jun 06 20:29:44 1997 from 128.122.209.198
| Jenn=> hi |
| wachsmut=> Hi Rob, |
| wachsmut=> looks like we're gathering a crowed ! |
| Rob=> hi Jenn and Bert! |
| Rob=> and Don |
| wachsmut=> David might not make it tonight, he said, |
| wachsmut=> so we're waiting for two more people ... |
=> [Don] leaves at Fri Jun 06 20:30:48 1997
| wachsmut=> let's wait for a couple of minutes, then we start |
| wachsmut=> looks like we lost Don, hope he'll be back ! |
=> [Don] joins at Fri Jun 06 20:31:14 1997 from 206.173.45.39
| wachsmut=> 2 more minutes - I've something cool today, if it works ! |
| wachsmut=> quick question: everybody using Windows 95 right now ? |
| Don=> yes |
| Rob=> yes |
| wachsmut=> Jenn, I hope you too ? |
| wachsmut=> |
| wachsmut=> hmmmm .... |
| wachsmut=> |
| wachsmut=> Jenn, are you using Windows 95 right now ? |
| wachsmut=> Well ... |
| wachsmut=> hm, looks like Jenn lost her voice .... |
| wachsmut=> anyway, let's do a few questions first, |
| wachsmut=> then I'll answer some questions, if any, |
| wachsmut=> then we'll take a look at something new, but |
| wachsmut=> it will not be so overwhelming as last time .... |
=> [Jenn] leaves at Fri Jun 06 20:34:22 1997
| wachsmut=> Alright, here we go ...... |
| wachsmut=> anyone who knows, just say it ... |
| wachsmut=> What's the basic class for almost every Java program ? |
=> [Jenn_] joins at Fri Jun 06 20:35:03 1997 from 199.174.147.190
| wachsmut=> What's the basic class for almost any Java program ? |
| wachsmut=> I.e. which class from the awt do you start out with .... |
| Rob=> You mean the "superset" almost all classes will extend? |
| Rob=> component? |
| Don=> java.awt.Frame |
| wachsmut=> Well ... Frame is right ! |
| wachsmut=> what does GUI stand for ? |
| Don=> graphical user onterface |
| Don=> whoops |
| wachsmut=> Great, thanks .... |
=> [aisha] joins at Fri Jun 06 20:36:33 1997 from 149.150.86.4
| wachsmut=> interface ... well, good enough |
| wachsmut=> give me an example of a GUI component, |
| wachsmut=> i.e. a class for it ... |
| Rob=> Can I try frame this time? |
| wachsmut=> please ... |
| wachsmut=> yes, frame, another one ? |
| Rob=> button |
| wachsmut=> good .... another one ???? |
| Don=> is TextCompnent one?? |
| wachsmut=> Right, but |
| wachsmut=> TextComponent is more abstract |
| wachsmut=> TextField and TextArea extend TextComponent, and are |
| wachsmut=> more useful .... we'll do those in the next lecture.... |
| wachsmut=> Here's another one: |
| wachsmut=> what's the name of the method to make a frame visible ? |
| wachsmut=> i.e. a frame is invisible by default, and you need to use which |
| wachsmut=> method to make it actually appear on the screen ? |
| wachsmut=> 'show()' .... did you do your readings ???????????? |
| Don=> show |
| wachsmut=> thanks .... guess you did -:) |
| wachsmut=> what's the name of the method to react to events such as a |
| wachsmut=> click on a button ..... |
| wachsmut=> or better, which method responds to a user action such as a |
| wachsmut=> click on a button ? |
| wachsmut=> well ? Anyone ? |
| Don=> ActivateEvent i think? |
| wachsmut=> too much ... |
| wachsmut=> just 'action' .... |
| wachsmut=> To review: |
| wachsmut=> To create a program, you 'extend Frame' .... |
| wachsmut=> then you add GUI components such as 'Button's .... |
| wachsmut=> Finally, the 'action' method is always part of a Frame, |
| wachsmut=> and since your class extends Frame, the action method will be |
| wachsmut=> part of your class. Therefore, what must you do in your class |
| wachsmut=> to achive your goals of your programs ? |
| wachsmut=> (Hint: your class must do something to the 'action' method) |
| Rob=> override it? |
| wachsmut=> Yes ! |
| wachsmut=> That's the basic Java program: |
| wachsmut=> extend Frame |
| wachsmut=> add GUI componets |
| wachsmut=> override 'action' |
| wachsmut=> that's all there's too it, for simple programs. |
| wachsmut=> Alright, that's my questions..... |
| wachsmut=> what aobut yours ? Any questions ? |
| Rob=> I have a few... I think mostly clarifications. |
| wachsmut=> First, please everybody say 'aye' ..... |
| Rob=> aye |
| Don=> aye |
| wachsmut=> just checking if you can 'hear me' .... |
| Jenn_=> aye |
| wachsmut=> Thanks, rob, don ... how about Aisha ? |
| wachsmut=> thanks Jenn_ |
| wachsmut=> Aisha had problems before, I know, maybe she can only |
| wachsmut=> 'see', but not answer ... that's what happened to her before.... |
| wachsmut=> oh well, so Rob, shoot ! |
| aisha=> i'm here |
| wachsmut=> YEAH !!!!! |
| Rob=> The only way we know what methods a class has it to look at the class AND |
| Rob=> all of its superclasses, right? |
| wachsmut=> Right ! |
| Rob=> Ok. |
| Rob=> Next |
| Rob=> We've just seen for the first time instantiating an object in a class that.. |
| Rob=> was not a "main" (program) class. |
| Rob=> I'm referring to TestFrame. |
| wachsmut=> Well, not really .... |
| wachsmut=> remember the 'Shape' things ? |
| wachsmut=> We instantiated Rectangles and Circles, and |
| wachsmut=> they did not contain a 'main' method ..... |
| Rob=> hmm. ok. |
| wachsmut=> It's the same with 'TestFrame', except that |
| Rob=> Last one. |
| wachsmut=> that class has zillions of methods, |
| wachsmut=> because it extends Frame which extends .... blah blah |
| wachsmut=> Alright, Rob .. |
| Rob=> Actually, I'll hold off on the last one... I think I got it. |
| wachsmut=> Great..... but, maybe somebody else had the same question, |
| wachsmut=> so .... what was it ? |
| Rob=> ok. here goes: |
| Rob=> You list some existing classes along with selected methods, for example: |
| Rob=> class java.awt.TextComponent extends java.awt.Component |
| wachsmut=> yes ... |
| Rob=> with the selected methods public String GetText(), etc. |
| Rob=> Now, what does the body of these methods look like? |
| wachsmut=> Ahhhh .... great question ! |
| wachsmut=> Actually, I don't know. |
| Rob=> I know, in general, like all other methods! |
| wachsmut=> The Java Virtual Machine is not entirely public ! |
| wachsmut=> The Component class, and the TextComponet class, and all classes |
| wachsmut=> in the awt and in the other packages comprise the JVM |
| wachsmut=> actually, to be more precise, they are all part of the JVM (Java |
| wachsmut=> Virtual Machine), and there's more. |
| wachsmut=> If you install the 'JDK', there's a 'zipped' file somewhere, called |
| Rob=> java.src? |
| wachsmut=> 'classes.zip' - that contains the 'packages', including the awt classes, but |
| wachsmut=> you can't unzip it, or JDK won't work. |
| wachsmut=> There's also a 'src' directory, and that contains the unzipped classes, |
| wachsmut=> at least many of them. You can find the method body there, |
| wachsmut=> but I have never bothered. I treat objects as 'black boxes' .... |
| wachsmut=> All I need is the header, and perhaps a brief description, and |
| wachsmut=> I don't care *how* the method works, as long as it *does* work. |
| wachsmut=> Alright, great question .... |
| wachsmut=> Don, Jenn_, Aisha, any questions ? |
| Don=> not yet |
| aisha=> not right now |
| Jenn_=> no |
| wachsmut=> Welll .... here we go, then, with something entirely new, but |
| wachsmut=> not too much (I hope). |
| wachsmut=> |
| wachsmut=> Remember, you can add 'components' to a frame, like buttons. |
| wachsmut=> The big question is: where do they go ! |
| wachsmut=> That's determined by what's called a 'layout' manager .... |
| wachsmut=> Java has 5 such layout managers, and 3 are easy. |
| wachsmut=> I will describe what the three easy ones do, |
| wachsmut=> then I'll show you examples and you have to identify |
| wachsmut=> them .... alright, read carefully: |
| wachsmut=> |
| wachsmut=> a FlowLayout Manager arranges all components in a row, |
| wachsmut=> and each one gets as much room as needed. |
| wachsmut=> |
| wachsmut=> a GidLayout arranges all components in a table-like grid with rows and |
| wachsmut=> columns, and each component gets the same size, so that the |
| wachsmut=> largest one determines the size of each other one. |
| wachsmut=> |
=> [aisha] leaves at Fri Jun 06 20:59:24 1997
| wachsmut=> a BorderLayout has 5 areas: east, west, south, north, and center, and the |
| wachsmut=> 'center' area gets all 'leftover' space. |
| wachsmut=> |
| wachsmut=> Alright, there they are: FlowLayout, GidLayout, and BorderLayout. |
| wachsmut=> Now: all of you are using Windows 95, and |
| wachsmut=> the "allow show" thing above the names is checked for all ? |
| wachsmut=> Yes or no ? |
| Don=> yes |
| Jenn_=> yes |
| wachsmut=> I mean there's a little checkbox above the names of the participants... |
| wachsmut=> Make sure it's checked ! |
| Rob=> yes |
| wachsmut=> Good.... I'll now make, by magic, a new screen appear on your |
| wachsmut=> computer. Take a good look, identify the layout, close that screen, |
| wachsmut=> and tell me what it was: Flow, Border, or Grid ... |
| wachsmut=> alright, here we go ... say 'what? ' if nothing happens in a few seconds.. |
| Jenn_=> grid? |
| wachsmut=> Yes, exactly. |
| Don=> grid |
| wachsmut=> Everything had the same size ! |
| wachsmut=> and was rectangular laid out, in a table. |
| wachsmut=> Everybody back here ? Please say ' yes '.... |
| Don=> yes |
=> [Rob] leaves at Fri Jun 06 21:03:22 1997
| Jenn_=> yes |
| wachsmut=> Rob ? |
| wachsmut=> Looks like we 'lost' Rob, let's hope he'll be back soon ! |
| Rob=> |
| wachsmut=> Here's another example. Take a look |
| wachsmut=> then close the screen and identify .... alright, wait a little ... |
| wachsmut=> What was it ? |
| Don=> flow |
| Jenn_=> |
| wachsmut=> Great ... why was it not a Grid with one row ? |
| wachsmut=> wanna see it again ? |
| Jenn_=> ok |
| wachsmut=> alright, here it is, one more time ... why not a 'Grid' with one row ? |
| Don=> because everything was not the same size? |
| wachsmut=> Exactly, very good ! |
| wachsmut=> alright, here's another one .... |
| wachsmut=> everybody ready ? Please say 'yep' ... or 'whatever' .... |
| Don=> yep |
| Rob=> aye |
| Rob=> aye |
| wachsmut=> let's wait for Jenn_ .... Jenn_ are you ready for another one ? |
| wachsmut=> perhaps not, we're dwindling in numbers .... |
| wachsmut=> anyhow, here's one more ! Hang on for a few seconds ..... |
=> [Jenn] leaves at Fri Jun 06 21:08:02 1997
=> [Jenny] joins at Fri Jun 06 21:08:18 1997 from 206.175.110.153
| wachsmut=> Hi Jenny .... |
| Jenny=> sorry i got disconnected.... |
| wachsmut=> we just took a look at the 3rd example, |
| wachsmut=> I'll show another one soon ... |
| wachsmut=> what was example 3 ? |
| Don=> border |
| wachsmut=> sure , after all, there are only three ! |
| wachsmut=> Alright .... |
| wachsmut=> that's rather limiting, but the good news is that you can |
| wachsmut=> 'mix and match' those layouts. |
| wachsmut=> So, I'll show you another one, and that |
| wachsmut=> combines at least 2 layouts, somehow. Please identify |
| wachsmut=> both layouts ..... |
| wachsmut=> all ready ? |
| Jenny=> yes |
| Rob=> yes |
| wachsmut=> alright, here we go (I assume Don's ready, too ... -:) |
| Don=> yep |
| wachsmut=> Alright, seen it ? What was it ? Two layouts: |
| Don=> flow and grid? |
| wachsmut=> yes ! |
| wachsmut=> flow for the buttons, |
| wachsmut=> and a grid (2 by 2) for the rest ! |
| wachsmut=> But, there's one more, actually: a borderlayout |
| wachsmut=> to put the 'flow' and the 'grid' together ! |
| wachsmut=> See what I mean ? In the center is the 'grid' layout with 2 rows, 2 cols, |
| wachsmut=> and 'south' is the flowlayout, with the buttons. |
| wachsmut=> So, there's three layouts, altoghter, and that makes for a rather nice |
| wachsmut=> 'small program'. |
| wachsmut=> Two more, if you don't mind, then we're done ..... |
| wachsmut=> Alright, ready ? |
| Rob=> let 'er rip. |
| wachsmut=> got it ? What was it ? |
| wachsmut=> (sorry, this one takes a while to load, I guess) ..... |
| Rob=> looks possibly like flow across the top and grid again below that? |
| Don=> all three again |
| Don=> or what rob said |
| wachsmut=> Yes, Rob's right, and Don put'em together with a Border, but |
| wachsmut=> this time, the 'flow' is 'south' in the 'border', and the 'grid, 2 rows, 3 cols, |
| wachsmut=> is at the 'center' of the 'border' |
| wachsmut=> Opps, sorry |
| wachsmut=> 'flow' is 'North', nothing is 'South'..... |
| wachsmut=> Alright - we'll learn in the next lecture how to put |
| wachsmut=> these layouts together ..... |
| wachsmut=> The final (yes, I know, you want to go ...) example I have is this: |
| wachsmut=> well .... it's different.... |
| wachsmut=> I'll show you the source code of a Java program. Please study it |
| wachsmut=> carefully. I want to know the folllowing: |
| wachsmut=> - how many buttons |
| wachsmut=> - what layout |
| wachsmut=> - how to instantiate that class |
| wachsmut=> - what does it do .... |
| wachsmut=> So .... after I show you the code, take 5 minutes, exactly, to look at it |
| wachsmut=> to try to see what it does. Remember, you need to look for the fields, |
| wachsmut=> the constructor, and then special methods such as 'action' .... |
| wachsmut=> Ready ? Remember, five minutes exactly ! |
| wachsmut=> Ready ? please say 'yes' ..... |
| Rob=> yes |
| Don=> yes |
| Jenny=> yes |
| wachsmut=> alright, here we go ... 5 mintues.... |
| wachsmut=> Alright .... how many buttons ? |
| Don=> 3 |
| Rob=> yep |
| wachsmut=> great .... |
| wachsmut=> what layout ? Perhaps Jenny ? |
| Jenny=> flow? |
| wachsmut=> Exactly ! |
| wachsmut=> how do you instantiate that class, i.e. |
| wachsmut=> TestFrame f = new ???? |
| wachsmut=> well, the constructor of the class requires an input |
| Rob=> = new TestFrame("yadda yadda"); |
| wachsmut=> parameter of type String , so YES, THAT's CORRECT ! |
| wachsmut=> So, here's the biggy ... |
| wachsmut=> what's it do ? |
| Don=> keeps arunning total and allows the user to reset it |
| wachsmut=> Exactly ! |
| wachsmut=> So, here's the wrapup .... |
| wachsmut=> Rob suggested an example in the discussion ... |
| Rob=> I know what's coming! |
| wachsmut=> I'll expand on it, and that would be a good portfolio suggestion .... |
| wachsmut=> Also, the TestFrame from above would be okay, IF you can |
| wachsmut=> add a feature such as a 'Subtract' button, and make it work |
| wachsmut=> correctly .... |
| wachsmut=> so .... I'll formalize those, and post them soon |
| wachsmut=> Other than that, this is it for today, but one quick question : |
| wachsmut=> next chat, is Monday at 8:30 okay ? |
| Jenny=> i have a night class |
| wachsmut=> I.e. is Monday perhaps better than Sunday ? |
| Don=> I may be alittle late or have trouble or together |
| wachsmut=> I see, Jenny .... |
| Don=> on monday |
| wachsmut=> Alright, Sunday 8:00pm good then ? |
| Rob=> This week I cannot make Sunday, but if that's the only time for everyone |
| Rob=> else, so it goes. |
| Rob=> Any possibility of later Monday? |
| Don=> whatever is easiest for everybody |
| wachsmut=> who votes for Sunday, who for Monday ? |
| wachsmut=> Stand up and be counted .... |
| Jenny=> sunday is better forme... |
| Rob=> I can only make it on monday. |
| Don=> moday around 9:00 or anytime sunday |
| wachsmut=> Don, the decisive vote .... |
| wachsmut=> Jenn, Monday 9:00 ???? |
| wachsmut=> If no, then it's Sunday, 8:00 - your call. |
| Jenny=> i don't get home till 10:00 =I |
| wachsmut=> Alright, Sunday, 8:00pm (sorry, Rob -:) |
| Don=> alright, sunday 8:00 |
| wachsmut=> So, guys, hope you liked this chat .... |
| wachsmut=> and mediate over this question as you sign off: |
| wachsmut=> what layout is this 'chat' applet (after all, it's in Java, so |
| wachsmut=> it's got to be something ..... -:) |
| wachsmut=> Class over ! I'll hang around for a few minutes, |
| wachsmut=> other than that - have a great weekend, see you Sunday .... |
| Don=> you too, bye |
=> [Don] leaves at Fri Jun 06 21:32:39 1997
| wachsmut=> if you have questions, go right ahead ... bye, Don ... |
| Jenny=> bye, have a good weekend! |
=> [Jenny] leaves at Fri Jun 06 21:32:42 1997
| wachsmut=> bye Jenn |
| Rob=> Hmmm, I was going to ask about setup(), pack() and show()... |
| wachsmut=> Go ahead .... |
| wachsmut=> setup is actually easy - |
| Rob=> If it's a long response we can let it go for now. |
| wachsmut=> not really, here's a quick answer: |
| Rob=> I just want to knwo what they do... |
| wachsmut=> 'setup()' is easy: it's defined below. It's not overridden, nor overloaded, |
| wachsmut=> it's simply a new method used only in this particular class. |
| wachsmut=> 'setup()' does not exist by 'default', i.e. in a Frame or anything.... |
| wachsmut=> it only does what I say it does. |
| wachsmut=> 'pack()' resizes the frame so that |
| wachsmut=> all componets fit as best as possible. |
| wachsmut=> It's very handy ... the frame will automatically find its optimum |
| wachsmut=> shape and size. |
| wachsmut=> 'show()' simply makes the frame visible (since by default |
| wachsmut=> it's invisible) .... |
| Rob=> ok ,,, and validate() |
| wachsmut=> Yes ... validate() make sure that all components that |
| wachsmut=> are added are 'valid' .... tell you the truth, I don't know exactly what |
| wachsmut=> it does ... but |
| wachsmut=> |
| wachsmut=> validate(); |
| wachsmut=> pack(); |
| wachsmut=> show(); |
| wachsmut=> are the 'standard' last lines in a class that extends Frame |
| wachsmut=> if you want the frame to correctly add all components and |
| wachsmut=> give itself the best possible size .... |
| Rob=> got it... thanks! |
| wachsmut=> No problem .... |
| wachsmut=> alright, more questions ? |
| wachsmut=> did you like this 'showing' of web pages ? |
| Rob=> Yes. |
| Rob=> Very creative -- and a productive demo. |
| wachsmut=> thanks ... I liked it, too -:) |
| wachsmut=> alright, then .... anything else ? |
| Rob=> ok... sorry I can't make it on Sunday. I'll check the transcript afterwards. |
| Rob=> signing off. |
| wachsmut=> bye .... |
| Rob=> bye |
=> [Rob] leaves at Fri Jun 06 21:40:07 1997
=> [wachsmut] leaves at Fri Jun 06 21:40:10 1997
