How to justify LabelField in Blackberry - blackberry

Question

I have long text content and I want to display it on screen with justify alignment using LabelField or something else. Currently, I can do right/left/center align but can't justify align.
Are there any custom controls that help me do this?

Answer 1

This is just a prototype, so there may be some things it doesn't handle. But, it should be a start, that you can use to do what you want. Most of the important logic is in the paint() method.
I'm not aware of any built-in (RIM libraries) way to do this.
public class JustifiedLabelField extends LabelField {
/** a cache of the label's words, to avoid having to recalculate every
time paint() is called */
private String[] _words;
/** the dynamic field height */
private int _height = 0;
public JustifiedLabelField(Object text, long style){
super(text, style);
setText(text);
}
public void setText(Object text) {
// update the words cache when text changes
_words = split((String)text, " "); // NOTE: this only supports String type!
super.setText(text);
}
public int getPreferredHeight() {
// I believe overriding this method is necessary because the
// justification might produce a different total number of lines,
// depending on the algorithm used
return (_height > 0) ? _height : super.getPreferredHeight();
}
protected void paint(Graphics g) {
Font font = g.getFont();
int space = font.getAdvance(' ');
int fontHeight = font.getHeight();
int fieldWidth = getWidth();
int word = 0;
int y = 0;
while (word < _words.length) {
// each iteration of this loop handles one line
int wordsInLine = 0;
int lineWordWidths = 0;
// first loop over all words that fit on this line, to measure
while (word < _words.length) {
int wordWidth = font.getAdvance(_words[word]);
if (lineWordWidths + wordWidth <= fieldWidth) {
lineWordWidths += (wordWidth + space);
word++;
wordsInLine++;
} else {
break;
}
}
// how much total space (gap) should be placed between every two words?
int gapSpacing = 0;
if (word == _words.length) {
// don't justify at all on last line
gapSpacing = space;
} else if (wordsInLine != 1) {
gapSpacing = (fieldWidth - (lineWordWidths - wordsInLine * space)) / (wordsInLine - 1);
}
int x = 0;
// now actually draw the words, with added spacing
for (int j = word - wordsInLine; j < word; j++) {
int span = g.drawText(_words[j], x, y);
x += span + gapSpacing;
}
y += fontHeight;
}
_height = y;
}
}
The above code makes use of a String split() method. You can find one possible implementation here.
Then, use the class like this:
public LabelScreen() {
super(MainScreen.VERTICAL_SCROLL | MainScreen.VERTICAL_SCROLLBAR);
String loremIpsum = "Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Nam cursus. Morbi ut mi. Nullam enim leo, egestas id, condimentum at, laoreet mattis, massa. Sed eleifend nonummy diam. Praesent mauris ante, elementum et, bibendum at, posuere sit amet, nibh. Duis tincidunt lectus quis dui viverra vestibulum. Suspendisse vulputate aliquam dui. Nulla elementum dui ut augue. Aliquam vehicula mi at mauris. Maecenas placerat, nisl at consequat rhoncus, sem nunc gravida justo, quis eleifend arcu velit quis lacus. Morbi magna magna, tincidunt a, mattis non, imperdiet vitae, tellus. Sed odio est, auctor ac, sollicitudin in, consequat vitae, orci. Fusce id felis. Vivamus sollicitudin metus eget eros.";
JustifiedLabelField label = new JustifiedLabelField(loremIpsum, Field.NON_FOCUSABLE);
add(label);
}
producing this:
Limitations
I don't do anything to account for things like padding in this field
LabelField allows you to call setText() or the constructor, with other types, not just String. My class only supports String, but you could easily expand that.
My class splits the string on spaces (' ') only. You may want to support splitting on other characters, or even inserting dashes to break really long words. I'll leave that to you.
I didn't test any edge cases, like words that were longer than could fit in the field width. I only tested this with a full screen width field, with small to medium-sized words.
see Eugen's comments on the page I link to for the split() method used
Follow-Up
I refined the code posted above a bit, and posted it online here. The newer version should handle padding, which this version does not. It should also handle vertical size issues if you pick a string splitting algorithm that changes how many lines the LabelField superclass thinks the field should have. More comments, too.