i seem to have a nullPointerException without any reason, could you please review piece of my code and tell me your opinion?
This is the class and the constructor that i am calling on another class in order to get a label randomly (using the shuffle, which is randomizing as well) from a linked list.
here is the
public class RandomHeuristic {
GameInterface game;
JLabel randomLabel;
public JLabel RandomHeuristic() {
randomLabel = (JLabel) game.labels.getFirst();
int counter = 0;
do {
Collections.shuffle(game.labels);
randomLabel = (JLabel) game.labels.getFirst();
counter++;
if (counter == 100) {
break;
}
/*
* Debugging
* System.out.println(randomLabel.getText());
*/
} while (randomLabel != null && game.isLegalMove(randomLabel) == false);
//Retrieves and removes the head (first element) of this list.
if(randomLabel == null){
RandomHeuristic();
}
//game.labels.remove(randomLabel);
return randomLabel;
}
}
And here is where i am calling the constructor, the playHeuristicMove() is expecting a JLabel i checked it on debugging that is working correctly, though i still get a nullPointer Exception when i call it. randomHeuristicOne is created on the same class like this: RandomHeuristic randomHeuristicOne;
playHeuristicMove(randomHeuristicOne.RandomHeuristic());
Perhaps you want to take a look at your game GameInterface object it seems it's never been instantiated
Related
I have been using TMP objects in several instances in my game, but all of a sudden it decides not to work on a certain object.
public class BeforeRoundTimer : MonoBehaviour
{
public TextMeshProUGUI timer;
private Timer oneSecondTimer;
private int time = 5;
public void StartCountdown()
{
Debug.Log("One second timer");
oneSecondTimer = new Timer(1000);
oneSecondTimer.Elapsed += UpdateTime;
oneSecondTimer.Enabled = true;
oneSecondTimer.AutoReset = true;
oneSecondTimer.Start();
}
private void UpdateTime(object source, ElapsedEventArgs e)
{
if(time == 0)
{
oneSecondTimer.Stop();
return;
}
timer.text = $"{time}";
time--;
}
}
I know the text is updating because I put debug statements (I have since removed them) and they fired when UpdateTime() is called. I also viewed the inspector when the game was playing, and the text value would update in front of my eyes. The text only changes when I make some stylistic change to it (i.e. making it bold, changing the font asset, including changing the text itself). I have looked back to my old code and it basically runs the exact same way, but it actually changes in game.
Ok so after taking a break, I decided to find another way to call my method every second. Instead of using a Timer, I decided to use Unity's InvokeRepeating() function.
public class BeforeRoundTimer : MonoBehaviour
{
public TextMeshProUGUI timer;
private int count = 0;
public void StartCountdown()
{
InvokeRepeating(nameof(UpdateTime), 0, 1f);
}
private void UpdateTime()
{
if(count == 5)
{
CancelInvoke("UpdateTime");
return;
}
Debug.Log("Update Time");
timer.text = $"{5 - count}";
count++;
}
}
One thing I noticed when trying to use the Timer in a different way is that it was only updating the text value every other second. It ran 10 times (I put a Debug.Log() in UpdateTime()) but only changed the value every other time while not actually updating the TMP. You could replace nameof(UpdateTime) with "UpdateTime", but Visual Studio recommended that I use the former so I went with that.
In short: don't use timers, use Unity's InvokeRepeating() function because it works perfectly. It is actually very similar to JavaScript's setInterval() which I found interesting.
Please excuse me I'm a complete novice at all this but I'm trying to make a game following "Brackeys How To Make A Video Game" I'm on video 8 if that helps. I can't seem to find what i have done wrong i have added my scripts for "player movement", "player collision" and "game manager". Please if there is anything else you need to help me please ask i really don't want to give up just yet was really enjoying doing this.
Thank you all
using UnityEngine;
public class PlayerMovement : MonoBehaviour {
// This is a reference to the Rigidbody component called "rb"
public Rigidbody rb;
public float forwardForce = 2000f; // Variable that determines the forward force
public float sidewaysForce = 500f; // Variable that determines the sideways force
// We marked this as "Fixed"Update because we
// are using it to mess with physics.
void FixedUpdate ()
{
// Add a forward force
rb.AddForce(0, 0, forwardForce * Time.deltaTime);
if (Input.GetKey("d")) // If the player is pressing the "d" key
{
// Add a force to the right
rb.AddForce(sidewaysForce * Time.deltaTime, 0, 0, ForceMode.VelocityChange);
}
if (Input.GetKey("a")) // If the player is pressing the "a" key
{
// Add a force to the left
rb.AddForce(-sidewaysForce * Time.deltaTime, 0, 0, ForceMode.VelocityChange);
}
if (rb.position.y < -1f)
{
FindObjectOfType<GameManager>().EndGame();
}
}
}
using UnityEngine;
public class PlayerCollision : MonoBehaviour {
public PlayerMovement movement; // A reference to our PlayerMovement script
// This function runs when we hit another object.
// We get information about the collision and call it "collisionInfo".
void OnCollisionEnter (Collision collisionInfo)
{
// We check if the object we collided with has a tag called "Obstacle".
if (collisionInfo.collider.tag == "Obstacle")
{
movement.enabled = false; // Disable the players movement.
FindObjectOfType<GameManager>().EndGame();
}
}
}
using UnityEngine;
using UnityEngine.SceneManagement;
public class GameManager : MonoBehaviour {
bool gameHasEnded = false;
public float restartDelay = 1f;
public GameObject completeLevelUI;
public void CompleteLevel ()
{
completeLevelUI.SetActive(true);
}
public void EndGame ()
{
if (gameHasEnded == false)
{
gameHasEnded = true;
Debug.Log("GAME OVER");
Invoke("Restart", restartDelay);
}
}
void Restart ()
{
SceneManager.LoadScene(SceneManager.GetActiveScene().name);
}
}
when i fall off ground:
NullReferenceException: Object reference not set to an instance of an object
PlayerMovement.FixedUpdate () (at Assets/Scripts/PlayerMovement.cs:32)
when i hit an obstacle:
NullReferenceException: Object reference not set to an instance of an object
PlayerCollision.OnCollisionEnter (UnityEngine.Collision collisionInfo) (at Assets/Scripts/PlayerCollision.cs:15)
It seems to me that FindObjectOfType<GameManager>() is returning null, which is causing a null reference exception when you attempt to call the EndGame function. This most likely means that there is no object in your scene with the GameManager component on it. The solution to this problem is simple:
Create an empty object in your scene and add the GameManager component to it. This will fix the error in this instance, but it could happen in the future if you're not careful. It is also a good idea to check if you found an object or not before calling functions on it:
GameManager gm = FindObjectOfType<GameManager>();
if (gm != null)
{
gm.EndGame();
}
I need basically an event that triggers at each 200 records loaded, so more data can be loaded until the end of data.
I tried to extend CharmListCell and using the method updateItem like this:
#Override
public void updateItem(Model item, boolean empty) {
super.updateItem(item, empty);
currentItem = item;
if (!empty && item != null) {
update();
setGraphic(slidingTile);
} else {
setGraphic(null);
}
System.out.println(getIndex());
}
But the System.out.println(getIndex()); method returns -1;
I would like to call my backend method when the scroll down gets the end of last fetched block and so on, until get the end of data like the "infinite scroll" technique.
Thanks!
The CharmListCell doesn't expose the index of the underlying listView, but even if it did, that wouldn't be of much help to find out if you are scrolling over the end of the current list or not.
I'd suggest a different approach, which is also valid for a regular ListView, with the advantage of having the CharmListView features (mainly headers and the refresh indicator).
This short sample, created with a single view project using the Gluon IDE plugin and Charm 5.0.0, shows how to create a CharmListView control, and fill it with 30 items at a time. I haven't provided a factory cell, nor the headers, and for the sake of simplicity I'm just adding consecutive integers.
With a lookup, and after the view is shown (so the listView is added to the scene) we find the vertical ScrollBar of the listView, and then we add a listener to track its position. When it gets closer to 1, we simulate the load of another batch of items, with a pause transition that represents a heavy task.
Note the use of the refresh indicator. When new data is added, we scroll back to the first of the new items, so we can keep scrolling again.
public class BasicView extends View {
private final ObservableList<Integer> data;
private CharmListView<Integer, Integer> listView;
private final int batchSize = 30;
private PauseTransition pause;
public BasicView() {
data = FXCollections.observableArrayList();
listView = new CharmListView<>(data);
setOnShown(e -> {
ScrollBar scrollBar = null;
for (Node bar : listView.lookupAll(".scroll-bar")) {
if (bar instanceof ScrollBar && ((ScrollBar) bar).getOrientation().equals(Orientation.VERTICAL)) {
scrollBar = (ScrollBar) bar;
break;
}
}
if (scrollBar != null) {
scrollBar.valueProperty().addListener((obs, ov, nv) -> {
if (nv.doubleValue() > 0.95) {
addBatch();
}
});
addBatch();
}
});
setCenter(new VBox(listView));
}
private void addBatch() {
listView.setRefreshIndicatorVisible(true);
if (pause == null) {
pause = new PauseTransition(Duration.seconds(1));
pause.setOnFinished(f -> {
int size = data.size();
List<Integer> list = new ArrayList<>();
for (int i = size; i < size + batchSize; i++) {
list.add(i);
}
data.addAll(list);
listView.scrollTo(list.get(0));
listView.setRefreshIndicatorVisible(false);
});
} else {
pause.stop();
}
pause.playFromStart();
}
}
Note also that you could benefit from the setOnPullToRefresh() method, at any time. For instance, if you add this:
listView.setOnPullToRefresh(e -> addBatch());
whenever you go to the top of the list and drag it down (on a mobile device), it will make another call to load a new batch of items. Obviously, this is the opposite behavior as the "infinite scrolling", but it is possible as well with the CharmListView control.
I want to implement a insertion method for a Binary search tree, and come up with a solution below. I know there are plenty of code examples but I wonder what is the problem in my implementation? Or is there a problem? When I had traced it I thought I have missed something.
public void insertBST(Node<Double> head, int value){
if (head == null){
head = new Node<Double>(value);
return;
}
else {
if (head.getValue() > value)
insertBST(head.getLeft(), value);
else
insertBST(head.getRight(), value);
}
}
When you reassign a passed parameter, you're only changing the local variable, not the value passed to the function. You can read this question for more information - Is Java "pass-by-reference"? This is Java, right? Either way, a similar argument likely applies.
This is the problem with this line of code:
head = new Node<Double>(value);
You aren't changing the value passed into the function, so you never add to the tree.
You have two alternatives here, either the option presented by amdorra, or returning the current node:
public void insertBST(Node<Double> current, int value)
{
if (current == null)
{
return new Node<Double>(value);
}
else
{
if (head.getValue() > value)
head.setLeft(insertBST(head.getLeft(),value));
else
head.setRight(insertBST(head.getRight(),value));
return current;
}
}
To call the function, you can simply say:
root = insertBST(root, value);
With alternatives, the root will have to be handled as a special case.
at the beginning of you function you are adding the new Node to a part you will never have access to outside this function
so i will assume that your Node class looks like the following
Class Node{
private Node left;
private Node right;
//constructor, setters and getters and stuff
}
you could modify your code to look like the following:
if (head.getValue() > value){
if(head.getLeft == null) {
head.setLeft(new Node<Double>(value));
return;
}
insertBST(head.getLeft(),value);
}
else{
if(head.getRight == null) {
head.setRight(new Node<Double>(value));
return;
}
insertBST(head.getRight(),value);
}
you should also remove this part if (head==null) and always make sure you are sending a valid Node to the first call
now I have this:
public void focusChanged(Field field, int eventType) {
if ( field == txtAmount && eventType == 1)
{
getVirtualKeyboard().setVisibility(VirtualKeyboard.HIDE);
}
}
Now my problem is that the keyboard isn't hiding. I think the error is in the eventType parameter. What number identifies a LostFocus event? I hard coded in '1' for tests but it doesnt seem to work.
FocusChangeListener focusListener;
//In the constructor:
txtAmount = new EditField(Field.FIELD_RIGHT);
txtAmount.setFocusListener(focusListener);
public void focusChanged(Field field, int eventType) {
if ( field == txtAmount && eventType == 1)
{
Dialog.alert("iasdi");
getVirtualKeyboard().setVisibility(VirtualKeyboard.HIDE);
}
}
why isn't this working? is there an enum or something that i can use to choose what eventType I should react to?
Also, if I remove the event type (so that the code executed regardless of the action just when focus changes right? nothing happens the dialog I put in for show, doesn't display meaniing the event is never entered. Any suggestions?
thanks
eventType can be one of next constants, declared in FocusChangeListener class:
public static final int FOCUS_GAINED = 1;
public static final int FOCUS_CHANGED = 2;
public static final int FOCUS_LOST = 3;
!!! Use FOCUS_LOST = 3 instead of FOCUS_GAINED = 1 to handle focus lost event.
Also, check for null getVirtualKeyboard() method returning value, because it returns null on touch devices without virtual keyboard (like Bold 9700).
public static void hideVirtualKeyboard() {
if (net.rim.device.api.ui.VirtualKeyboard.isSupported()) {
Screen screen = UiApplication.getUiApplication().getActiveScreen();
if (null != screen) {
net.rim.device.api.ui.VirtualKeyboard vk = screen
.getVirtualKeyboard();
if (vk != null) {
vk.setVisibility(net.rim.device.api.ui.VirtualKeyboard.HIDE);
}
}
}
}
For matching the eventType, try using the constants defined in FocusChangeListener instead of hard coding "1". In this case, you probably want to use FocusChangeListener.FOCUS_LOST.
As for the case of the code not running, are you actually setting the value of the "focusListener" variable? From the code you posted, you aren't and it will just be passing as "null" into setFocusListener().