I have a loop that takes file name from a listbox, performs a system() call, then moves that filename to another listbox. Problem is, it doesn't move the filenames over one at a time, but waits until the entire loop is finished and moves them all at once. What would I do to get it to perform how I want it to?
the loop:
for each( String^% file in filename )
{
int x = convert( file );
lbComplete->Items->Add( lbFiles->Items[0] ); // place the completed file
lbFiles->Items->Remove( lbFiles->Items[0] ); // in the other listbox
}
The function convert() that contains the system call:
int convert( String^ file )
{
std::stringstream ss;
std::string dir, fileAddress, fileName, outputDir;
...
return system( ss.str().c_str() );
}
It's very common in GUI programming that methods called from the "event thread" or "event loop" need to finish before the changes they make are seen on the screen. That's regardless of the language or the environment. The usual way to avoid that problem on the things I'm most familiar with (like Java Swing) is to do the updates outside of the event loop, but use notifications (swing events) to tell the GUI to update the display occassionally.
You would need to call a refresh function at the end of your loop forcing it to redraw your listboxes otherwise it will wait until after your loop to do so.
for each( String^% file in filename )
{
int x = convert( file );
lbComplete->Items->Add( lbFiles->Items[0] ); // place the completed file
lbFiles->Items->Remove( lbFiles->Items[0] ); // in the other listbox
// INSERT REFRESH FUNCTION HERE
}
Tell both listboxes to refresh themselves after moving an item.
Related
I have a problem that I still can't solve and it just doesn't want to work. Basically I have to convert a function into a composable.
In the old function I launched a Coroutine and at the result, I changed context and then continued with my processes. In compose I don't understand how I have to "change context" in order to continue.
Old code:
fun getMyView( activity: Activity
) {
backgroundCoroutineScope.launch {
//some stuff here
withContext(coroutineContext) {
startSearchView(
activity
)
}
}
}
New not working code:
#Composable
fun getMyView( content: #Composable() () -> Unit) {
LaunchedEffect(key1 = Unit) {
//some stuff here like old funciont
//here I don't know how to change context, wait the end and go ahead. startSearchViewis a composable function too
// i want to use it to populate my screen
startSearchView(
content
)
}
}
How can I solve it? Thanks
Seems like you are trying to asynchronously "create" composable function, but UI emitting doesn't work this way. Like #PylypDukhov suggested, you should keep a mutable state holding nullable result of your async action. After loading the data set this state. Then in composable just do something like:
if (data != null) {
SearchComposable(data)
}
This way the composable will be emitted after the data is loaded
I'm new to Jetpack Compose and I've spent some hours to find how to make a LazyColumn update what I update my list. I've read that it needs to be a immutable list to update LazyColumn, but I can't seem to get it to work.
The code looks like:
#Composable
fun CreateList() {
var myList : List<DailyItem> by remember { mutableStateOf(listOf())}
myList = getDailyItemList() // Returns a List<DailyItem> with latest values and uses mutable list internally
// Function to refresh the list
val onUpdateClick = {
// Do something that updates the list
...
// Get the updated list to trigger a recompose
myList = getDailyItemList()
}
// Create the lazy column
...
}
I have tried several things and either is the list never updated when tapping the update button or only the first item is updated but not the rest of the items in the list. I looked in the documentation and there it says this, but I don't understand it:
Instead of using non-observable mutable objects, we recommend you use
an observable data holder such as State<List> and the immutable
listOf().
How to update the list so the LazyColumn is updated?
Use SnapshotStateList, the list is mutable. Any modification (add, remove, clear, ...) to the list will trigger an update in LazyColumn.
Similar to mutableListOf() (for MutableList) there is mutableStateListOf() to create a SnapshotStateList.
Extention function swapList() just combines clear() and addAll() calls to replace old list with new list.
fun <T> SnapshotStateList<T>.swapList(newList: List<T>){
clear()
addAll(newList)
}
#Composable
fun CreateList() {
val myList = remember { mutableStateListOf<DailyItem>() }
myList.swapList(getDailyItemList()) // Returns a List<DailyItem> with latest values and uses mutable list internally
// Function to refresh the list
val onUpdateClick = {
// Do something that updates the list
...
// Get the updated list to trigger a recompose
myList.swapList(getDailyItemList())
}
// Create the lazy column
...
}
See the basic idea is to get compose treat the list as state. Now that, you are able to achieve using mutableStateOf(initialValue),
Okay, the process is this,.
We create a variable, initialising it as a mutable state of something
Then we assign that variable to the lazy column. It is not necessary to assign it to the items parameter of the column, but that is our use case here. Otherwise, inside the Composable containing the lazy column, you could just type the name of the variable and even that will work since all we want, is compose to get a message that this variable is being read by the Composable.
Back to the question,
We create a variable, say val mList: List<Int> by remember { mutableStateOf (listOf()) }
Lazycolumn{
items(items = mList){
Text(it)
}
}
Button(onClick = { mList = mList + listOf(mList.size())})
Clicking the button adds a new number to the list, which is reflected in the LazyColumn's UI.
I was following a tutorial for creating a 2d space shooter. It was working fine until I added code to spawn enemy mobs, now it just runs but it's frozen. I can't understand why it wont work. there are no errors anywhere or anything like that.
Thanks.
You have a minor typo with the brackets in your update method.
protected override void Update(GameTime gameTime)
if (GamePad.GetState(PlayerIndex.One).Buttons.Back == ButtonState.Pressed || Keyboard.GetState().IsKeyDown(Keys.Escape))
Exit();
//updating mobs and checking for collisions
foreach (Mobs M in mobsList)
{
// Updating the mobs, collision checking, etc here
...
...
Player.update(gameTime);
bG.update(gameTime);
loadAsteroids();
loadMobs();
foreach (Roids R in asteroidList)
{
// Updating the asteroids, collision checking, etc
...
...
M.update(gameTime);
R.update(gameTime);
}
base.Update(gameTime);
}
}
There are two main things wrong in this. Firstly, this bit of code:
Player.update(gameTime);
bG.update(gameTime);
loadAsteroids();
loadMobs();
foreach (Roids R in asteroidList)
{
// Updating the asteroids, collision checking, etc
...
M.update(gameTime);
R.update(gameTime);
}
base.Update(gameTime);
Will be run inside the first foreach loop. You are updating the player, the background, every asteroid, and the window once for each mob, every time you call update. This is only meant to happen once per update, not once per mob that is being updated. This is why your gaming is lagging or freezing. This is just a misplacement of the bracket on the mob's foreach loop - shift all this stuff outside the foreach loop.
The other thing wrong is this part:
foreach (Roids R in asteroidList)
{
// Updating the asteroids, collision checking, etc
...
M.update(gameTime); /* THIS LINE HERE */
R.update(gameTime);
}
Here, you are updating each Mob member once per asteroid. If you have 15 asteroids on screen, each mob member will be updated 15 times. Shift that line up into the first foreach loop.
I have successfully implemented like this for lazy loading in custom list
and the code I used for this is here:Custom List With Images in Blackberry
In the linked question, I position the y coordinate of heart icon and I resolved the problemm of linked Question.
if (logoThumbnailImage != null
&& logoThumbnailImage.length > index
&& logoThumbnailImage[index] != null) {
EncodedImage img = logoThumbnailImage[index];
graphics.drawImage(0, y + 10, Display.getWidth(),
Display.getHeight() - 100, img, 0, 0, 0);
graphics.drawImage(300,
y+400,
heart.getWidth(), heart.getHeight(), heart,
0, 0, 0);
Now I want to handle click event for both; that is, for list row click and on heart click
For that I saw a post written by #Nate here Custom List Field click event. But in that code the images are not loading from server and they are static Images. I want to implement #Nate's code with my code (That is lazy loading ).
If you have any Idea please suggest how can I do that. Thanks in Advance
Assuming you start with the code I posted in this answer, and use the code you show in this question to download images from a list of URLs, then you should be able to achieve lazy image loading with the following changes:
Create a listener interface that gets notified when downloads complete:
public interface DownloadListener {
// invokes if download success
public void downloadSuccess(Bitmap bitmap);
// invokes if download failed
public void errorOccured();
}
Then, the Manager subclass that represents one list row, CustomListRow, is modified to implement this interface, and update the _thumb image when the download completes:
public class CustomListRow extends Manager implements DownloadListener, FieldChangeListener {
public void downloadSuccess(final Bitmap img) {
_data.setThumb(img);
// make sure bitmap is updated on the UI / main thread
UiApplication.getUiApplication().invokeLater(new Runnable() {
public void run() {
_thumb.setBitmap(img);
}
});
}
public void errorOccured() {
// TODO: handle error
}
Then, you'll need to add some code to create all your threads to download images in the background, and notify the DownloadListeners when the image downloads complete. You can decide where to do this. In my example, I will do this in my ListScreen class, where I instantiate the ListRander data objects and the CustomListField:
for (int i = 0; i < numberOfItem; i++) {
ListRander lr = new ListRander("Product Name " + i, icon); // icon is placeholder for thumbnail image
data.addElement(lr);
}
final CustomListField list = new CustomListField(data);
add(list);
list.setChangeListener(this);
pool = new ThreadPool(3); // 3 concurrent download threads
for (int i = 0; i < numberOfItem; i++) {
final int row = i;
// create a new runnable to download the next image, and resize it:
pool.assign(new Runnable() {
public void run() {
try {
String text=object[row].getJSONArray("UrlArray").getString(0).toString();
EncodedImage encodedImg = JPEGEncodedImage.encode(connectServerForImage(text), quality); //connectserverForImage load Images from server
EncodedImage logoThumbnail = sizeImage(encodedImg, Display.getWidth(), Display.getHeight()-100);
list.getRow(row).downloadSuccess(logoThumbnail.getBitmap());
} catch (Exception e) {
e.printStackTrace();
list.getRow(row).errorOccured();
}
}
}
});
}
You could do this in the ListScreen constructor, or whenever you have your object[] array of URLs.
You'll need to add a new method to CustomListField:
public CustomListRow getRow(int row) {
return (CustomListRow)getField(row);
}
The code above also needs a member variable added (in ListScreen) to create a thread pool:
private ThreadPool pool;
This thread pool implementation is based on this tutorial here, with very minor modifications, simply to change ArrayList (not available on BlackBerry Java) to Vector ... and removing the calls to Thread#destroy(). You'll need to copy that tutorial's ThreadPool, WorkerThread, and Done classes to your project. The above example I show creates a thread pool of 3 threads. On a single CPU smartphone, 2 or 3 threads is probably fine for your needs. Read more here if you want to get the perfect number of threads for your application.
Note: if possible, you can usually improve performance if you download images that are exactly the right size for your application, instead of burdening the network with larger images, and then resizing them inside your app. However, I realize that this depends on having some control over the images' web server, which you may not have. Just a thought for later optimization.
I am sure that I seen a good answer to this question on my travels, but can't find it now. I do recommend reviewing the BB forums here:
http://supportforums.blackberry.com/t5/Java-Development/bd-p/java_dev
as there are similar questions there.
For now, just the highlights of what you need to do:
Create an image downloading runnable to process the download - you have pretty much already done this in your previous code.
Use the Observer pattern (search the internet for this), so that the BitmapField is the Observer for the completion of your image downloading. So when the image has been downloaded, the Runnable invokes the observer, which can then update the Bitmap.
Use a Thread pool with a limited number of Threads (I would say 3), so that you do not start a whole load of image downloads at the same time. Search the internet for information on Thread Pool for help implementing this. You had not done this step in your previous example, and you can get away with running all the downloads, but I expect at some stage that this will fail.
Put these together and you have your solution. Not trivial I know. Good luck.
I'm trying to write a function on a MovieClip, and call it from the root clip. What works fine in ActionScript 3 doesn't seem to be working properly in ActionScript 2.
Frame 1 of the _root MovieClip:
var newMovieClip:MovieClip = _root.attachMovie('Notification', id, 0);
newMovieClip.SetNotificationText("Test text");
Frame 1 of the Notification MovieClip:
function SetNotificationText(inputText : String){
notificationText.text = inputText;
}
The result is that the MovieClip is created but the text is not changed.
Am I doing this wrong?
To add functions to a MovieClip in AS2, you need to use one of these methods:
Add the method to the prototype of MovieClip:
MovieClip.prototype.SetNotificationText = function(inputText:String):Void
{
if(this["notificationText"] !== undefined)
{
// If we're going to use the prototype, at least do some checks
// to make sure the caller MovieClip has the text field we expect.
this.notificationText.text = inputText;
}
}
newMovieClip.SetNotificationText("Test text");
Make the MovieClip and argument of the function:
function SetNotificationText(mc:MovieClip, inputText:String):Void
{
mc.notificationText.text = inputText;
}
SetNotificationText(newMovieClip, "Test text");
Add the method directly to the newly created MovieClip:
var newMovieClip:MovieClip = _root.attachMovie('Notification', id, 0);
newMovieClip.SetNotificationText(inputText:String):Void
{
notificationText.text = inputText;
}
newMovieClip.SetNotificationText("Test text");
Option 2 is best overall - it's the cleanest and avoids overhead of creating a new function for every new MovieClip. It also avoids messing around with the prototype, which at best should be used to add generic methods, like a removeItem() method on Array.