Here's the deal, I need to run an operation, and show a progress bar while it runs. I figured I need to run the progress bar update on a different thread, because if I don't (I have tried) the bar doesn't get updated before the end of the operation. I have written the code bellow, however it isn't working, crashing the app instead. I believe the problem is related to the synchronization between threads, but I'm not sure (second time working with Java threads, please spare me, I'm still a newbie). This is running on Android.
Can you spot any illegal operation I'm not aware of? Thanks!
ProgressDialog progress; //Global, declared somewhere else
final Object flag = new Object();
Thread progressThread;
//More Code...
progress.show();
progress.setMax(auxMobile.size() + auxStatic.size() );
progress.setProgress(0);
progressThread = new Thread(new Runnable() {
#Override
public void run() {
try {
synchronized (flag) {
while (progress.getProgress() < progress.getMax()) {
progress.incrementProgressBy(1);
flag.wait();
}
}
} catch (InterruptedException e) {
e.printStackTrace();
}
}
});
progressThread.start();
try {
for(int i=0; i<auxStatic.size(); i++) {
//More Code...
flag.notify();
}
for(int i=0; i<auxMobile.size(); i++){
//More Code...
flag.notify();
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
You really should use AsyncTask in that case.
Check this, this.
It's gonna make your dev life for that case a hell lot easier !
Related
I'm having an app which enables a customer to place an order for a ride (as in Uber), initially considered in a "WAITING" phase. When a driver accepts the order, it is automatically set in an "ACCEPTED" phase.
When ACCEPTED, the user is going to be redirected to another scene, telling him that he needs to wait for his rider to pick him up.
I decided to create a thread that checks every 250ms if the status of his order was set to ACCEPTED, like that:
public class AcceptanceRunnable implements Runnable {
private boolean running;
public AcceptanceRunnable() {
running = true;
}
public void run() {
do {
try {
Thread.sleep(250);
} catch (InterruptedException e) {
e.printStackTrace();
}
if (OrderService.checkIfAccepted(OrderSession.getOrder())) {
// move to other scene
break;
}
} while(running);
}
public void setRunning(boolean running) {
this.running = running;
}
}
This AcceptanceRunnable class gets instantiated within the controller in the initialize() method:
#FXML
public void initialize() throws InterruptedException, IOException {
sourceAddress.setText("From: " + OrderSession.getOrder().getSourceAddress());
destinationAddress.setText("To: " + OrderSession.getOrder().getDestinationAddress());
price.setText("You'll need to pay RON " +
UserService.calculatePrice(UserSession.getUser()) + " for this ride.");
acceptanceRunnable = new AcceptanceRunnable();
Thread t = new Thread(acceptanceRunnable);
t.start();
}
Everything works fine. If I just print out some lines while waiting for the order's status to get changed, it seems to be okay. The problem is, I want my user to be redirected to another scene, if his order gets accepted.
This means, I need to insert something in place of the comment made in my AcceptanceRunnable.run() method.
I also tried changing the scene by having a method called ifAccepted() inside my controller, which actually triggers the method that changes the scene:
if (OrderService.checkIfAccepted(OrderSession.getOrder())) {
try {
Class<?> controller = Class.forName("com.example.yuber.controllers.CustomerWaitController");
Method ifAccepted = controller.getMethod("ifAccepted");
ifAccepted.invoke(controller.newInstance());
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
} catch (NoSuchMethodException e) {
e.printStackTrace();
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (InstantiationException e) {
e.printStackTrace();
}
break;
}
But I only get some NullPointerException and I'm pretty sure that what I do here isn't really correct.
Any opinions?
As Slaw suggested, using Platform#runLater(Runnable) fixed my problem.
What I actually did was add my run() method from the Runnable inside my controller, renaming it to handleTread():
public void handleThread() {
do {
try {
Thread.sleep(250);
} catch (InterruptedException e) {
e.printStackTrace();
}
if (OrderService.checkIfAccepted(OrderSession.getOrder())) {
Platform.runLater(() -> {
try {
SceneService.NewScene("/com/example/yuber/accepted-view.fxml", (Stage) rootPane.getScene().getWindow(), rootPane.getScene());
} catch (IOException e) {
e.printStackTrace();
}
});
break;
}
} while(running);
}
Not using Platform.runLater(...) would result in receiving a Not on FX Application Thread error.
Everything seems to be fine now.
How to create your own listener that listens to the OS efficiently in Java? For example like the ActionListener in Swing, that reacts to button clicks.
I want to make a program that logs the users clipboard, but I don't want to use a loop like this:
while (flag)
{
Transferable t = Toolkit.getDefaultToolkit()
.getSystemClipboard()
.getContents(null);
if (t != null && t.isDataFlavorSupported(DataFlavor.stringFlavor))
{
try
{
String text = (String) t
.getTransferData(DataFlavor.stringFlavor);
System.out.println(text);
}
catch (UnsupportedFlavorException e1)
{
e1.printStackTrace();
}
catch (IOException e1)
{
e1.printStackTrace();
}
}
Thread.sleep(1000);
}
I want the processor only to work when the clipboard changed and not check every second if that is the case.
Secondly I found a Method that might work
this.clipboard = Toolkit.getDefaultToolkit()
.getSystemClipboard();
this.clipboard.addFlavorListener(new FlavorListener()
{
#Override
public void flavorsChanged(FlavorEvent e)
{
// work with the clipboard contents
}
});
But still I need a strange while loop that consumes processor time to keep the program active.
I think that I should use wait and notfiy, but I'm not sure how.
I tried to use multiple threads, sadly no luck:
public synchronized boolean pingServer(final String ip, final short port) {
final boolean[] returnbol = new boolean[1];
Thread tt = new Thread(new Runnable() {
#Override
public void run() {
try {
Socket s = new Socket(ip, port);
s.close();
returnbol[0] = true;
} catch (IOException e) {
returnbol[0] = false;
}
}
});
tt.start();
try {
tt.join();
} catch (InterruptedException e) {
tt.stop();
}
tt.stop();
return returnbol[0];
}
The main thread still Freezes for some reason.
Is there a "lagless" way to ping a server?
What exactly did you want to got in
try {
tt.join();
} catch (InterruptedException e) {
tt.stop();
}
block?
Here you joined to parallel thread and waits till this thread will ends (got ping result).
You have next options:
Wait till ping ends
Don't wait... and don't got result
Use some concurrency classes like Future<> to got result (but you will block thread at moment you ask result if it not retrieved yet)
Or you can use some 'callback' function/interface to threw result from inner 'ping' thread.
You will need to remove the following lines from your code.
The tt.join() will force the main thread to wait for tt to finish.
try {
tt.join();
} catch (InterruptedException e) {
tt.stop();
}
tt.stop();
Use a Future instead to get the result for later use
Okay, I got the following code from the web, and it does work:
#Override
public void fileTransferRequest(FileTransferRequest request) {
// Check to see if the request should be accepted
final IncomingFileTransfer transfer = request.accept();
runnningFileTransfer = transfer;
try
{
final File file = new File("/Users/Akku/Downloads/in2" + request.getFileName());
transfer.recieveFile(file);
t = new Thread(new Runnable() {
#Override
public void run() {
// TODO Auto-generated method stub
try {
transfer.recieveFile(file);
System.out.println("DONE?");
} catch (XMPPException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
});
t.run();
This code runs, and in the case of my 10MB test file it takes quite a lot of time. Sadly, I need to know if the transfer is finished or what the progress is. Funnily, I also got this part (which just sleeps and checks for progress) from the web, when I append it, the file transfer does not work anymore:
while(!transfer.isDone())
{
if(transfer.getStatus().equals(Status.error))
{
System.out.println("ERROR"+transfer.getError() + " EX: " + transfer.getException());
}
else
{
System.out.println("Written: "+transfer.getAmountWritten());
System.out.println("STATUS"+transfer.getStatus());
System.out.println("PROGRESS"+transfer.getProgress());
}
try
{
Thread.sleep(10000);
System.out.println("Waiting...");
}
catch (Exception e)
{
e.printStackTrace();
}
}
Any hint why this might happen? I guess it's something Java, because the above snippet works flawlessly.
The case that works should be throwing an exception. You call receive twice on the transfer object. The second call should produce an exception when it tries to create the file again. The second call, along with the thread creation is not necessary in this case as the transfer() method is asynchronous and has it's own internal threading.
It is hard to say why it doesn't work with your status check, since you don't show where you are doing this check. My suspicion is that you are calling it on the read thread and thus blocking the reading of new packets. Your loop checking for the transfer status should be running in its own thread.
I'm currently developping a ftp client based on the package commons.net, in order to run tests to see the speed of the connection.
Basically my ftp test consists in connect to the server, logging onto it, and then start a cycle of download/upload as long as necessary, until the user decides to stop it via a button, then the current cycle will end and so will the test.
However, while running those tests, a situation requiering a timout mechanism has occured. the server was transmitting the file, and send the return code 226 (transfer complete) before it was indeed completed.
So my thread remains stuck, trying to empty the inputStream when it is not possible anymore.
My idea was to start a threaded timer with the downloading process, that will be reset each time a byte is transferred to my client.
When the timeout occurs, then an exception or so would be raised, and my client would react to it, abording the download.
I have read and try many solutions, among them:
- raising an exception from a thread -> the thread catches the exception and not the client;
- interrupt the client from the thread, so the client raises itself an interruptedException -> doesn't seem to work;
- using an executor with a timeout -> since I can't know the "normal" duration of a download, I can't give it to the executor when I start the task, moreover, the timer has to be reset when I receive data.
I read a lot about it on many forums, and didn't find any solution that seem to be adapted AND work in this case. If anyone has an idea of another way to do it?
This is the code of the action I am performing:
public double get(String fileName) {
[...]
org.apache.commons.net.io.Util.copyStream(stO,stD,client.getBufferSize(),
this.localSize,
new org.apache.commons.net.io.CopyStreamAdapter() {
public void bytesTransferred(long totalBytesTransferred,
int bytesTransferred,long streamSize) {
setProgressDL(totalBytesTransferred);
//reset the timer here
}
});
[...]
}
Here is some of the code of my test, launching my client:
public class TestFtp extends Thread {
[...]
public void run() {
System.out.println("Launching FTP test");
FtpClient client = new FtpClient(this.model, this, this.model.getFtpServer());
try {
//Attempting connection on the server
client.connect();
try {
// Attempting login
client.login(this.model.getUsername(), this.model.getPassword());
do {
client.changeDirectory("get");
// start timer
client.get(this.model.getDistantFileName());
// stop timer
client.changeToParentDirectory();
client.changeDirectory("put");
client.set(this.model.getDistantFileName(),
this.model.getNewFileName());
client.changeToParentDirectory();
try {
// Little pause between each test
Thread.sleep(500);
} catch (InterruptedException e) {}
// Continue test until the user stops it
} while (this.continuous);
// Once the test is over, logout
client.logout();
} catch (FTPLoginException e) {
// If login fails, the test ends
System.out.println("Unable to login to the server.");
}
} catch (FTPConnectException e) {
// If connection error, the test ends
System.out.println("Unable to connect to the server.");
}
}
Thank you by advance if anyone can help, and if you need further information on my actual code, I can put more of it in here.
If you do not want to throw unecessary Exceptions, you should use a boolean flag that controls the execution of the thread (or runnable):
public class TestFtp extends Thread {
[...]
boolean abort;
public void run() {
[...]
do{
[...]
} while (this.continuous && !abort);
if (abort){
// You might want to do something here
}else{
// The stuff you normally do
}
}
}
And then simply set the abort flag to false from outside.
This way you can better control how you thread will terminate, as thread.interrupt(); will have an undefined behavior.
Well, I'm sorry but I admit I haven't read all your code, but if you want to interrupt a running thread, do two things:
run the thread code inside a try/catch block like this:
Example:
public void run() {
try {
// code to run
} catch (InterruptedException ie) {
// thread interrupted, may want to do some clean up
// but must return as quickly as possible to avoid halting external code
}
}
Call the interrupt() method of the thread above externally when the need arises.
Example:
thread.interrupt();
This will tell the VM to throw the InterruptedException in your thread no matter what it's doing, giving you a chance to do some stuff.
I hope this is what you're looking for...
EDIT
Ok, a concrete example that works:
public class Driver {
private static int count = 0;
public static void main(String[] args) {
Thread t = new Thread(new Runnable() {
#Override
public void run() {
try {
bigTask();
} catch (InterruptedException ie) {
System.out.println("Interrupted thread! Count is " + count);
}
}
});
t.start();
try {
Thread.sleep(1000);
System.out.println("Trying to interrupt thread");
t.interrupt();
} catch (InterruptedException e) {}
}
private static void bigTask() throws InterruptedException {
List<BigDecimal> bigs = new ArrayList<BigDecimal>();
for (int i = 0; i < 10000000; i++) {
bigs.add(BigDecimal.valueOf(i));
if (Thread.interrupted()) {
throw new InterruptedException();
}
count = i;
}
System.out.println("Ok, added ten million items, count is " + count);
}
}