ListBox Sorting

[sidkdbl07]

I'm tring to sort a ListBox alphabetically with the following
function. Does anybody have any better ideas?

public void sortListBox(ListBox box) {
if(box.getItemCount() > 1) {
for(int i=0; i<box.getItemCount(); i++) {
if(box.getItemText(i).substring(0,3).compareTo(box.getItemText(i
+1).substring(0,3)) > 0) {
box.insertItem(box.getItemText(i), i+2);
box.removeItem(i);
}
}
}
}

[abickford]

java.util.Arrays is supported. Assuming your list is actually backed
by a string array:

String[] items = { "pear", "apple", "banana" };
Arrays.sort(items);

The items array is now sorted.

[Peter Blazejewicz]

hi,

something similiar,
I wonder what will be faster,

public class ImageViewer implements EntryPoint {
private Button clickMeButton;
private ListBox listBox;

private native void addToArray(JavaScriptObject array, int i, String
text)/*-{
array[i] = text;
}-*/;

public void onModuleLoad() {
RootPanel rootPanel = RootPanel.get();
clickMeButton = new Button();
rootPanel.add(clickMeButton);
clickMeButton.setText("Sort items");
clickMeButton.addClickListener(new ClickListener() {
public void onClick(Widget sender) {
sortItems(listBox);
}
});
listBox = new ListBox();
rootPanel.add(listBox, 5, 46);
listBox.addItem("banana");
listBox.addItem("apple");
listBox.addItem("orange");
listBox.addItem("pear");
listBox.addItem("grape");
listBox.setSize("163px", "328px");
listBox.setVisibleItemCount(5);
}

private void sortItems(ListBox list) {
int size = list.getItemCount();
JavaScriptObject array = JavaScriptObject.createArray();
for (int i = size - 1; i >= 0; --i) {
addToArray(array, i, list.getItemText(i));
}
updateList(array, list);
}

private native void updateList(JavaScriptObject array, ListBox list)/
*-{
array.sort();
for(i = 0; i<array.length; i++){
this.@com.mycompany.project.client.ImageViewer::updateList(Lcom/
google/gwt/user/client/ui/ListBox;ILjava/lang/String;)(list, i,
array[i]);
}
}-*/;

private void updateList(ListBox list, int index, String text) {
list.setItemText(index, text);
}
}

regards,
Peter

[sidkdbl07]

I guess the issue that I have is that the ListBox items have a value
and a text. I guess I would use a struct of some sort and then sort
the struct. Oh well, it gives me some ideas. Thanks. Keep the ideas
flowing.

[Peter Blazejewicz]

hi,

> I guess the issue that I have is that the ListBox items have a value
> and a text.

these is not recommended (i would use jre emulation instead) but it is
just working (and requires quick modification of previous sample):

public class ImageViewer implements EntryPoint {
private Button clickMeButton;
private ListBox listBox;

private native void addToArray(JavaScriptObject array, int i, String

text, String value)/*-{
array[i] = {text: text, value:value};
}-*/;

public void onModuleLoad() {
RootPanel rootPanel = RootPanel.get();
clickMeButton = new Button();
rootPanel.add(clickMeButton);
clickMeButton.setText("Sort items");
clickMeButton.addClickListener(new ClickListener() {
public void onClick(Widget sender) {
sortItems(listBox);
}
});
listBox = new ListBox();
rootPanel.add(listBox, 5, 46);

// use key/value
listBox.addItem("Potato", "Potatoes");
listBox.addItem("banana", "Bananas");
listBox.addItem("apple", "Apples");
listBox.addItem("orange", "Oranges");
listBox.addItem("pear", "Pears");
listBox.addItem("grape", "Grapes");

listBox.setSize("163px", "328px");
listBox.setVisibleItemCount(5);
}

private void sortItems(ListBox list) {
int size = list.getItemCount();
JavaScriptObject array = JavaScriptObject.createArray();
for (int i = size - 1; i >= 0; --i) {

addToArray(array, i, list.getItemText(i), list.getValue(i));
}
updateList(array, list);
StringBuffer sb = new StringBuffer();
for(int i = 0; i<listBox.getItemCount(); i++){

sb.append("key:").append("\t").append(listBox.getItemText(i)).append("\t");

sb.append("value:").append("\t").append(listBox.getValue(i)).append("\n");
}
Window.alert("sorted:\n"+sb.toString());
System.out.println(sb.toString());
}

private native void updateList(JavaScriptObject array, ListBox list)/
*-{

//var sort = function(
array.sort(function(a, b){
if(a.text.toLowerCase()>b.text.toLowerCase()){
return 1;
} else if(a.text.toLowerCase()<b.text.toLowerCase()){
return -1;
}
return 0;

});
for(i = 0; i<array.length; i++){
this.@com.mycompany.project.client.ImageViewer::updateList(Lcom/

google/gwt/user/client/ui/ListBox;ILjava/lang/String;Ljava/lang/
String;)(list, i, array[i].text, array[i].value);
}
}-*/;

private void updateList(ListBox list, int index, String text, String
value) {
list.setItemText(index, text);
list.setValue(index, value);
}
}

key: apple value: Apples
key: banana value: Bananas
key: grape value: Grapes
key: orange value: Oranges
key: pear value: Pears
key: Potato value: Potatoes

regards,
Peter

[sidkdbl07]

private native void updateList(JavaScriptObject array, ListBox list)

is not found in JSNI when i try to compile.

Any ideas?

[sidkdbl07]

I don't understand the following line...

th...@com.mycompany.project.client.ImageViewer::updateList(Lcom/
google/gwt/user/client/ui/ListBox;ILjava/lang/String;Ljava/lang/

What do I replace the 'th...' with?

[mP]

read the jsni pages that come with the download. It explains all that
you need to know about "native" java methods which are used to include
javascript within a comment. What you are seeing is the mechanism that
javascript code uses to refer to java variables/methods etc.

[mP]

You really should be sorting the list prior to actually creating the
ListBox items, using Arrays.sort( Object[], Comparator ). Adding/
removing items as one does when sorting is going to be much slower
than sorting a list of objects.

You can provide your own comparator if need be.
Arrays.sort( Object[] ) simply sorts if the array contains types that
are Comparable. Read the javadoc for String, java.util.Comparator,
java.util.Comparable.

[Peter Blazejewicz]

hi,

this is because of safety html strip on groups I think,

it should reads (exluding quotes!) "this.@"

regards,
Peter