I am working on an application in android. And I am trying to update data to UI from the background thread. However, it doesn't work for some reasons. Can any one splot the error or suggest any better solution? I used Thread to read data from the bluetooth socket and update the UI with RunOntheUI. Here is the code:
socket = belt.createRfcommSocketToServiceRecord(UUID_SECURE);
socket.connect();
stream = socket.getInputStream();
// final int intch;
Thread timer2 = new Thread() { // Threads - do multiple things
public void run() {
try {
// read data from input stream if the end has not been reached
while ((intch = stream.read()) != -1) {
byte ch = (byte) intch;
b1.append(ByteToHexString(ch) +"/");
decoder.Decode(b1.toString());
runOnUiThread(new Runnable() {
public void run()
{
// update the uI
hRMonitor.SetHeartRateValue((int) decoder.GetHeartRate());
}
});
Thread.sleep(1000);
}
} catch (Exception e) {
e.printStackTrace();
}
}};
timer2.start();
use
Your_Current_Activity.this.runOnUiThread(new Runnable() {
#Override
public void run() {
hRMonitor.SetHeartRateValue((int) decoder.GetHeartRate());
}
});
instead of
runOnUiThread(new Runnable() {
public void run()
{
// update the uI
hRMonitor.SetHeartRateValue((int) decoder.GetHeartRate());
}
});
No. You MUST NOT do that. Never use another thread to update UI Thread, because UI Thread is not thread-safe, it means : when you update your UI Thread, UI Thread doesn't stop working for you do some stuff.
And Android has a machism for this work. This is Asyntask : it will create another thread and when need, it will has safe way to update UI Thread. If you want to more detail, Asyntask will drop a message to message queue of UI Thread.
Here is another link of my post about different Thread, Handler and Asyntask. Asyntask
Hope this help :)
Related
I'm trying to animate something when a task is completed. The problem here is I get this error message:
android.util.AndroidRuntimeException: Animators may only be run on Looper threads
at android.animation.ValueAnimator.cancel(ValueAnimator.java:1004)
at android.view.ViewPropertyAnimator.animatePropertyBy(ViewPropertyAnimator.java:965)
at android.view.ViewPropertyAnimator.animateProperty(ViewPropertyAnimator.java:921)
at android.view.ViewPropertyAnimator.alpha(ViewPropertyAnimator.java:735)
at com.design.zaton.prototypei.MainActivity$1$1.run(MainActivity.java:93)
at java.lang.Thread.run(Thread.java:761)
The app worked fine before with the same exact code but now it simply doesn't. I'm really confused.
Here's where the error happens:
new Thread(new Runnable() {
#Override
public void run() {
final String s = getGiphyViews(String.valueOf(mEdit.getText()));
runOnUiThread(new Runnable() {
#Override
public void run() {
result.setText(s);
}
});
loading.animate()
.alpha(0)
.setDuration(100);
done.animate()
.scaleY(1)
.scaleX(1)
.setDuration(300);
}
}).start();
The error outlines the loading.animate() method.
Thanks in advance!
runOnUiThread(new Runnable() {
#Override
public void run() {
//Your code
}
});
You have to execute the code in the UI Thread
Looper threads are threads in Android that permanently loop (or until you cancel them). They work in conjunction with Handlers which will post and send messages to Looper threads. Animators use heavy use of Looper threads because they perform their actions in repeated cycles. This allows the animator to not block after you press "start" so you can continue to perform other actions.
To further complicate matters, you most likely are performing animations on View objects. These can only be run on the main UI thread (which happens to be the biggest Looper thread of them all). So, you can not run these animations on separate threads like you are trying.
I think, there has been a solution for this using Handler. You can use postDelayed to minimal as 100 and run your animating tasks. In your case it would be:
new Handler().postDelayed(new Runnable() {
#Override
public void run() {
final String s = getGiphyViews(String.valueOf(mEdit.getText()));
runOnUiThread(new Runnable() {
#Override
public void run() {
result.setText(s);
}
});
loading.animate()
.alpha(0)
.setDuration(100);
done.animate()
.scaleY(1)
.scaleX(1)
.setDuration(300);
}
}, 100);
I had this problem today and above work resolved the problem. I would love to hear from anyone if there is any problem with this method.
Kotlin
If you still want to use a delay (or not)
Handler(Looper.getMainLooper()).postDelayed({
// Your Code
}, 1000)
Put Code Where Are getting error and doing any network operations
new Handler().post(new Runnable() {
#Override
public void run() {
// add your code here
}
});
I think you can create a main handler instance in your activity and override handle message method. you can save a handler quote in your work thread.When you finished work you can use handler to send a message and you receive message in handle message method. To start animation from handler message method and so on...
I need to send a message to a HandlerThread from my current thread but stop the sendmessage call from returning immediately. Is there a way to do this sendMessage() in a blocking way?
This is what i think the solution should be.
// This handler will be associated with the UI thread
Handler uiHandler = new Handler() {
#Override
public void handleMessage(Message msg) {
textView.setText("Progress: " + msg.what);
}
};
private void CreateThread() {
Thread t = new Thread() {
public void run() {
for(int i = 0; i < cnt; i++)
{
try {
Thread.sleep(1000);
} catch (Exception e) {
Log.v("Error: ", e.toString());
}
// You can update the UI by sending messages to the UI thread
uiHandler.sendMessage(uiHandler.obtainMessage(i));
}
}
}
};
t.start();
}
Please take a look at the Exchanger class. I would create an exchanger, send a Runnable having access to that exchanger, and synchronize on that exchanger. This way the exchanger would give me the results obtained asynchronously. You may think out something that would work with messages.
Note that a thread that calls Exchanger.exchange() may have to wait for a long time! (You may get an ANR if you call it from the UI thread.)
This is a general Java question and not an Android one first off!
I'd like to know how to run code on the main thread, from the context of a secondary thread. For example:
new Thread(new Runnable() {
public void run() {
//work out pi to 1,000 DP (takes a while!)
//print the result on the main thread
}
}).start();
That sort of thing - I realise my example is a little poor since in Java you don't need to be in the main thread to print something out, and that Swing has an event queue also - but the generic situation where you might need to run say a Runnable on the main thread while in the context of a background thread.
EDIT: For comparison - here's how I'd do it in Objective-C:
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0UL), ^{
//do background thread stuff
dispatch_async(dispatch_get_main_queue(), ^{
//update UI
});
});
Thanks in advance!
There is no universal way to just send some code to another running thread and say "Hey, you, do this." You would need to put the main thread into a state where it has a mechanism for receiving work and is waiting for work to do.
Here's a simple example of setting up the main thread to wait to receive work from other threads and run it as it arrives. Obviously you would want to add a way to actually end the program and so forth...!
public static final BlockingQueue<Runnable> queue = new LinkedBlockingQueue<Runnable>();
public static void main(String[] args) throws Exception {
new Thread(new Runnable(){
#Override
public void run() {
final int result;
result = 2+3;
queue.add(new Runnable(){
#Override
public void run() {
System.out.println(result);
}
});
}
}).start();
while(true) {
queue.take().run();
}
}
In case you are on Android, using a Handler should do the job?
new Handler(Looper.getMainLooper()).post(new Runnable () {
#Override
public void run () {
...
}
});
An old discussion, but if it is a matter of sending request to the main thread (an not the opposite direction) you can also do it with futures. The basic aim is to execute something in background and, when it is finished, to get the result:
public static void main(String[] args) throws InterruptedException, ExecutionException {
// create the task to execute
System.out.println("Main: Run thread");
FutureTask<Integer> task = new FutureTask<Integer>(
new Callable<Integer>() {
#Override
public Integer call() throws Exception {
// indicate the beginning of the thread
System.out.println("Thread: Start");
// decide a timeout between 1 and 5s
int timeout = 1000 + new Random().nextInt(4000);
// wait the timeout
Thread.sleep(timeout);
// indicate the end of the thread
System.out.println("Thread: Stop after " + timeout + "ms");
// return the result of the background execution
return timeout;
}
});
new Thread(task).start();
// here the thread is running in background
// during this time we do something else
System.out.println("Main: Start to work on other things...");
Thread.sleep(2000);
System.out.println("Main: I have done plenty of stuff, but now I need the result of my function!");
// wait for the thread to finish if necessary and retrieve the result.
Integer result = task.get();
// now we can go ahead and use the result
System.out.println("Main: Thread has returned " + result);
// you can also check task.isDone() before to call task.get() to know
// if it is finished and do somethings else if it is not the case.
}
If your intention is to do several stuff in background and retrieve the results, you can set some queues as said above or you can split the process in several futures (starting all at once or starting a new one when needed, even from another future). If you store each task in a map or a list, initialized in the main thread, you can check the futures that you want at anytime and get their results when they are done.
You may want to use the 'even dispatching thread' where most event driven things happen. If you are using swing then:
SwingUtilities.invokeLater(new Runnable() {
public void run() {
Your code here.
}
});
Or create a class that implements Runnable and pass it into invokeLater().
If you're using JavaFX, which I highly recommend, then you can use
Platform.runLater(new Runnable() {
#Override
public void run() {
alert(text);
}
});
from within your non-UI thread, and the runnable will executed from the UI thread on return from your thread.
A little late to the party but I think that my approach is a little bit different.
Modifying Affe's solution a little bit
public static final BlockingQueue<Runnable> queue = new LinkedBlockingQueue<>();
public static void main(String[] args) {
Thread myThread = new Thread(
() -> {
String name = Thread.currentThread().getName();
System.out.println("initial current thread " + name);
queue.add(() -> System.out.println(Thread.currentThread().getName()));
});
myThread.setName("background thread");
myThread.start();
try {
myThread.join();
} catch (InterruptedException e) {
e.printStackTrace();
}
while (!queue.isEmpty()) {
try {
queue.take().run();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
output
initial current thread background thread
main
i have one problem with handling the thread in android ,in my class i have to create one thread which create some UI after that thread finish i will get some value ,here i want to wait my Main Process until the thread complete it process but when i put wait() or notify in Main process thread does not show the UI in my application
this is sample code
protected void onCreate(Bundle savedInstanceState) {
downloadThread = new MyThread(this);
downloadThread.start();
synchronized(this){
try {
this.wait();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
String test=Recognition.gettemp();
public class MyThread extends Thread {
private Recognition recognition;
public MyThread(Recognition recognition) {
this.recognition = recognition;
// TODO Auto-generated constructor stub
}
#Override
public void run() {
synchronized(this)
{
handler.post(new MyRunnable());
}
notifyAll();
}
}
}
static public class MyRunnable implements Runnable {
public void run() {
settemp(template);
}
}
}
public static String gettemp() {
return template;
}
public static void settemp(String template) {
Recognition.template = template;
}
}
here i will not use AsynTask because i have some other issue that is reason i choose Thread even now the problem is Thread wait do any give the suggestion for this
- Use java.util.CountDownLatch , here you can let some process complete before kick-off some other code.
- countDown() and await() will be of use to you.......
See this example of CountDownLatch:
http://www.javamex.com/tutorials/threads/CountDownLatch.shtml
Use the logic below :-
new Thread(new Runnable()
{
#Override
public void run()
{
//do the code here such as sending request to server
runOnUiThread(new Runnable()
{
#Override
public void run()
{
//do here the code which interact with UI
}
});
}
}).start();
What do you expect to happen if you freeze the main UI thread?
You should be using an ASyncTask to show your gui in the onPreExecute method, do the task in doInBackground then display the result in the onPostExecute method.
As a plus you can update the progress using onProgressUpdate too.
This is not an solution just a advice on how should you structure you activity/app.
You should never block the main thread by calling wait() its a bad user experience and not advised. It would also case a Android Not Responding (ANR) popup.
You can have you thread updating the UI from the background and let the UI to be responsive. Load the static part of your UI in onCreate() and then fire up the background thread to lazy load rest of the component.
I have an event handling mechanism in my Android code to dump the sensor values in a file. Right now, I'm doing it in the main UI thread and hence the UI button responsiveness is very sluggish and I would like to speed it up.
How can I use multithreading on event handling functions? I'm trying to do it like this:
Create a global variable writeNow.
When the sensor value changes, set WriteNow = true
Create a thread in the class which looks like this:
Thread thread1 = new Thread()
{
public void run()
{
if(writeNow == true)
{
try
{
fos.write(s.getBytes());
}
catch (IOException e)
{
e.printStackTrace();
}
writeNow = false;
}
}
};
Thus, whenever writeNow is true, it will write to a File and then set WriteNow to false. However, I realize this is not the right approach, because the thread will execute once and then stop executing. When I tried a simple example with a while(true) and wait(), I found that the thread is interrupted millions of times.
So how do I enclose this event handling mechanism in a single thread, for speeding up a process?
Thanks!
You can try one of the following approaches:
It looks like you're trying to keep your writer thread running all the time; what you can do is spawn the thread only when you need it. Take a look at the example in the Android documentation for handling expensive operation in the UI thread.
Here is the example from that page:
public class MyActivity extends Activity {
[ . . . ]
// Need handler for callbacks to the UI thread
final Handler mHandler = new Handler();
// Create runnable for posting
final Runnable mUpdateResults = new Runnable() {
public void run() {
updateResultsInUi();
}
};
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
[ . . . ]
}
protected void startLongRunningOperation() {
// Fire off a thread to do some work that we shouldn't do directly in the UI thread
Thread t = new Thread() {
public void run() {
mResults = doSomethingExpensive();
mHandler.post(mUpdateResults);
}
};
t.start();
}
private void updateResultsInUi() {
// Back in the UI thread -- update our UI elements based on the data in mResults
[ . . . ]
}
}
Since it doesn't look like you're doing anything in the UI thread once you finish writing you don't really need to bother with a Handler. But you might want to use it to display a Toast once the file has been written to.
On the other hand, if you still want to have a thread running, you might have it sleep() and periodically wake up and check the status of writeNow.
Thread thread1 = new Thread()
{
public void run()
{
while(true)
{
if(writeNow == true)
{
try
{
fos.write(s.getBytes());
}
catch (IOException e)
{
e.printStackTrace();
}
writeNow = false;
}
try
{
Thread.sleep(100); //sleep for 100 ms
}
catch (InterruptedException e)
{
Log.d('', e.getMessage());
}
}
}
};
Note that this will quickly get complicated and you might lose the bytes you want to write if your thread is sleeping when new data comes in and when it wakes up, even newer data has been received and has overwritten the previous bytes. You'd need some sort of a queue to manage that.
I'm not sure what you were doing with the wait() but that should've also worked and is in fact, the approach for problems involving a consumer and producer. The idea is to have your thread synchronize and wait() on a shared object (like perhaps your queue of bytes); a second thread will call notify() on the shared object when there is data available to write and the writer thread will be woken up. The writer thread should then write and reloop. Take a look at this tutorial.
As for the interruption of your thread, your thread may be interrupted for a number of reasons which is why it is good practice (especially when using wait()) to ensure that the condition you checked before you called wait() is still valid because you could've been woken because of either a call to notify()/notifyAll() or because of an interruption.
Handler handler = null;
handler = new Handler();
//create another class for and make consrtuctor as u want. so that u can use that effectively.
//for example.
popupIndex = new IndexThread(handler,head, target,ltp,price,IndexNifty.this,columsView,call);
popupIndex.setColumnViewexit(columsView);
handler.postDelayed(popupIndex, 300);
//another class
public IntraThread(Handler handler,String script,int target,int ltp,int price,Intraday intraday,TextView columsView,String call){
super();
this.target = target;
this.ltp = ltp;
this.price = price;
this.intraday = intraday;
this.columsView = columsView;
this.script= script;
this.handler= handler;
this.call= call;
}
public void run(){
// write ur code here....
}