问题
I'm running S60 with j2me using LWUIT in Eclipse.
I'm using this Tutorial Link.. for reference to draw list.
but as i printed the position of list element drawing but it called more than once (i think for 3-4 times) i don't understand why ?
And also responsiveness of list is also poor, takes lot of time to scroll down .
As i'e seen some video examples of LWUIT list they are working faster and smoother as my list can not why ??
My code to parse and add values to list from json received
public void setNotificationList(String response) {
if (!response.equals("") || response != null) {
try {
JSONObject jsonObject = new JSONObject(response);
if (jsonObject != null) {
if (jsonObject.getInt("total") > 0) {
totalNotificationPages = jsonObject
.getInt("total_pages");
JSONArray notificationJsonArray = jsonObject
.getJSONArray("notifications");
int lenghtOfList = notificationJsonArray.length();
if (!moreNotificationListFalg) {
notificationList = new List();
} else {
notificationVector.removeAllElements();
}
notificationVector = new Vector(lenghtOfList);
for (int i = 0; i < lenghtOfList; i++) {
JSONObject notificationJsonObjects = notificationJsonArray
.getJSONObject(i);
UpdatesUserData notificationData = new UpdatesUserData();
notificationData.user_id = JSONHelper
.getStringFromJSON(notificationJsonObjects,
"user_id");
notificationData._id = JSONHelper
.getStringFromJSON(notificationJsonObjects,
"id");
notificationData.message = JSONHelper
.getStringFromJSON(notificationJsonObjects,
"message");
notificationData.date = JSONHelper
.getStringFromJSON(notificationJsonObjects,
"created_at");
// Helper.stringToDate(JSONHelper.getStringFromJSON(notificationJsonObjects,
// "created_at"));
// Helper.createDate(JSONHelper.getStringFromJSON(notificationJsonObjects,
// "created_at"));
notificationData.distance = JSONHelper
.getStringFromParentJSON(
notificationJsonObjects, "user",
"distance");
if (notificationJsonObjects.has("user")) {
JSONObject jsonObjectParent = notificationJsonObjects
.getJSONObject("user");
notificationData.user_image = APIHelper
.getPictureUrl(
JSONHelper
.getStringFromParentJSON(
jsonObjectParent,
"profile",
"avatar_thumb"),
JSONHelper
.getStringFromParentJSON(
jsonObjectParent,
"profile",
"picture_url"));
}
System.out.println("User Image "
+ notificationData.user_image);
notificationVector.addElement(notificationData);
}// for loop ends
System.out.println("Displaying user Notification list");
// check if Update List Exists then remove it and Add
// this Notification List
if (form.contains(updateList)) {
form.removeComponent(updateList);
System.out.println(" Update List removed...");
}
if (form.contains(moreUpdates)) {
form.removeComponent(moreUpdates);
System.out.println(" moreUpdate removed... ");
}
// ----------------------------------------------------
// Getting index of lat element of List before adding
// new elements to it
int index = notificationList.size();
if (notificationVector.size() > 0) {
// Adding elements to notification vector
for (int i = 0; i < notificationVector.size(); i++) {
notificationList.addItem(notificationVector
.elementAt(i));
}
System.out.println("Adding List ");
if (!moreNotificationListFalg) {
notificationList
.setRenderer(new UpdatesListCellRenderer(
false));
form.addComponent(notificationList);
} else {
notificationList.setSelectedIndex(index - 1);
notificationList.repaint();
}
// Addgin more... Btn if pages are more than 1
if (totalNotificationPages > notificationPageNo)
form.addComponent(moreUpdates);
// Adding ActionListener to list
notificationList
.addActionListener(new ActionListener() {
public void actionPerformed(
ActionEvent arg0) {
form.setFocused(notificationTabBtn);
}
});
}
moreNotificationListFalg = false;// setting flag false
form.invalidate();
form.repaint();
} else {
System.out.println("List has not Elements to print.");
}
}
} catch (JSONException e) {
e.printStackTrace();
}
}
}
My render-er class
public class UpdatesListCellRenderer extends Container implements
ListCellRenderer {
private Label message = new Label("");
private Label distance = new Label("");
private Label profile_image = new Label("");
private Label date = new Label("");
private Label focus = new Label();
private Font font;
public Container base_container;
private Container containerY,containerX;
private Resources resources;
private boolean flag = false;
private Button moreUpdates = new Button();
public UpdatesListCellRenderer(boolean flag) {
try {
setCellRenderer(true);
this.flag = flag;
BorderLayout bl = new BorderLayout();
setLayout(bl);
base_container = new Container(new BoxLayout(BoxLayout.X_AXIS));
// cnt1.setWidth(width);
resources = Resources.open("/font.res");
font = resources.getFont("font1");
base_container.getStyle().setBgImage(
Image.createImage("/images/contact_list_background.png"));
profile_image.getStyle().setBgTransparency(0);
profile_image.setPreferredH(60);
profile_image.setPreferredW(70);
profile_image.getStyle().setAlignment(CENTER);
base_container.addComponent(profile_image);
containerY = new Container(new BoxLayout(BoxLayout.Y_AXIS));
// name.getStyle().setBgTransparency(0);
// name.getStyle().setFont(font);
message.getStyle().setBgTransparency(0);
message.getStyle().setFont(font);
containerX = new Container(new BoxLayout(BoxLayout.X_AXIS));
containerX.getStyle().setAlignment(BOTTOM);
containerX.getStyle().setMargin(25, 0, 0, 0);
distance.setAlignment(LEFT);
distance.setPreferredH(20);
distance.setPreferredW(85);
distance.getStyle().setBgImage(
Image.createImage("/images/long_right_arrow.png"));
distance.getStyle().setBgTransparency(0);
distance.getStyle().setFont(font);
date.setAlignment(RIGHT);
date.getStyle().setBgTransparency(0);
date.getStyle().setFont(font);
date.getStyle().setMargin(0, 0, 100, 1);
//moreUpdates.setVisible(false);
// containerY.addComponent(name);
containerY.addComponent(message);
containerX.addComponent(distance);
containerX.addComponent(date);
containerY.addComponent(containerX);
base_container.addComponent(containerY);
addComponent(BorderLayout.CENTER, base_container);
//addComponent(BorderLayout.SOUTH, moreUpdates);
focus.getStyle().setBgTransparency(100);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public Component getListCellRendererComponent(List list, Object value,
int position, boolean isSelected) {
UpdatesUserData notificationData = (UpdatesUserData) value;
try {
//System.out.println(" List get ListComponent Popstion " + position + " List size " + list.size());
//if (!notificationData.message.equals(""))
message.setText("" + notificationData.message);
// else
// message.setText("");
//if (!notificationData.distance.equals(""))
distance.setText("" + notificationData.distance);
// else
// distance.setText("" + notificationData.distance);
date.setAlignment(RIGHT);
//if (!notificationData.date.equals(""))
date.setText("" + notificationData.date.substring(0, 10));
// else
// date.setText("");
date.setAlignment(RIGHT);
profile_image.setIcon(Helper.loadImage(notificationData.user_image));
// if( position == list.size()-1){
// //base_container.addComponent(moreUpdates);
// //addComponent(BorderLayout.SOUTH, moreUpdates);
// moreUpdates.setVisible(true);
// }
} catch (IOException e) {
e.printStackTrace();
}
if (isSelected) {
list.setFocus(true);
list.getStyle().setBgTransparency(100);
} else {
list.setFocus(false);
list.getStyle().setBgTransparency(0);
}
return this;
}
public Component getListFocusComponent(List list) {
return focus;
}
}
Please help me ...
回答1:
Read Chen's post on the Codename One blog http://codenameone.blogspot.com/2008/07/lwuit-list-renderer-by-chen-fishbein.html
Generally a cell renderer will be called once for every visible item and when it is moved it will be called even more since there is an animation of the focus movement running in the background. S60 is really slow with translucent images, make sure that if you have 9-piece borders they don't contain images that are too small.
Compare performance to the LWUIT demo and see the difference.
回答2:
I think the problem in this code: profile_image.setIcon(Helper.loadImage(notificationData.user_image));. Try to use your render without this code or replace it with a stub image and let's see what will be.
回答3:
Ok, I suposse that it is printed so many times to refresh the state of the List
Are you using a ListModel attached to the List? That fact is important for the list's efficiency. How do you map your list's elements? Can you paste some code in your question?
回答4:
As i think list gets called for every element it contains to paint it. My problem is the same that i actually loading images from url in getListCellRendererComponent() that wrong i actually load it before( while parsing json) and store then pass it to list as Image. That thing improves my list list performance a lot.
by the way all of you thanks for the help..
来源：https://stackoverflow.com/questions/11414861/in-listcellrenderer-getlistcellrenderercomponent-method-called-more-than-once