Java Reference
In-Depth Information
or specifies the textfield's width in terms of displayable columns, where a column is
defined as an approximate average character width (and is platform-dependent).
Thefinalgridrowpresentsapairof Button instancesforperformingconversions.
the top textfield's text (via TextField 's String getText() method, which is
inherited from TextField 's TextComponent superclass), converting it to a num-
ber,andassigningittothebottomtextfieldbycalling TextField 'soverriding void
setText(String t) method.
After populating the panel, the constructor adds the panel to the frame window. It
then invokes pack() to ensure that the frame window is made large enough to dis-
play its components at their preferred sizes, invokes Frame 's void setResiz-
able(boolean resizable) methodwitha false argumenttopreventtheuser
from resizing the frame window (and making it look ugly), and invokes setVis-
ible() with a true argument to display the frame and its components.
Aftertheconstructorreturnsto main() ,thisclassmethodexits.However,theframe
cause the running EDT is a nondaemon thread (discussed in Chapter 4 ).
Compile Listing7-1 ( javac )andrunthisapplication( java
TempVerter ). Figure 7-4 shows the resulting GUI on the Windows XP platform.
Figure 7-4. Click the X button to close this window and terminate the application.
WhenyouenternonnumerictextorleavetheDegreestextfieldempty, TempVerter
outputsa“ bad input ”messagetothestandardoutputdevice.Also,whenyouclose
the window, this application outputs “ window closing ” followed by “ window
closed ” messages on separate lines.
Note You can move forward to the next component by pressing the Tab key, and
youtabtohasthe focus whenitcanobtaininput—theonly TempVerter components
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