(Apple problem # 3760180)
Summary:
The setCaretPosition method in a TextArea is unreliable in Java 1.4.2 Update 1.
Steps to Reproduce:
Run the Java applet on this page (source code below)
Example:
Run the applet in Safari.
Note whether the displayed text begins with "Four score and seven years ago".
If not, click the browser's Reload button.
Expected Results:
In every case, the displayed text should begin with "Four score and seven years
ago".
Actual Results:
About half the time the middle of the text passage is displayed, as one might
expect without the setCaretPosition(0) code. Often the display is proper
on initial loading but invariably the middle of the text is displayed within
several presses of the Reload button.
Workaround:
None.
Isolation:
In two larger applets the problem does not occur when the TextArea is displayed
in a Frame but does occur when it is not displayed in a Frame.
Testing was done on a slow G4 (400 MHz, 192 MB RAM). It is possible that timing/threading issues could be exposed only on slow machines.
This problem was present before 142Update1 but there were other TextArea display problems and it was not clear whether the problems were separate.
import java.applet.*;
import java.awt.*;
public class text_in_area2 extends Applet {
static final String TEXT = "Four score and seven years ago, our forefathers
brought forth on this continent a new nation conceived in liberty and dedicated
to the proposition that all men are created equal. Now we are engaged in a great
civil war testing whether that nation, or any nation so conceived and so
dedicated, can long endure. We are met on a great battlefield of that war. We
have come to dedicate a portion of that field as a final resting-place for those
who here gave their lives that that nation might live. It is altogether fitting
and proper that we should do this. But, in a larger sense, we cannot dedicate,
we cannot consecrate, we cannot hallow this ground. The brave men, living and
dead, who struggled here have consecrated it far above our poor power to add or
detract. The world will little note nor long remember what we say here, but it
can never forget what they did here. It is for us the living rather to be
dedicated here to the unfinished work which they who fought here have thus far
so nobly advanced. It is rather for us to be here dedicated to the great task
remaining before us that from these honored dead we take increased devotion to
that cause for which they gave the last full measure of devotion that we here
highly resolve that these dead shall not have died in vain, that this nation
under God shall have a new birth of freedom, and that government of the people,
by the people, for the people shall not perish from this earth.";
public void init()
{
setBackground(new Color(225,225, 255));
TextArea ta = new TextArea(TEXT, 4, 30,
TextArea.SCROLLBARS_VERTICAL_ONLY);
ta.setEditable(false);
add(ta);
ta.setCaretPosition(0);
}
} // END OF Class text_in_area2
If you have any insights, workarounds or comments about
this test page please contact Mickey
Segal. A listing of many Java resources is at this link.