I've seen some similar questions and got some information but they stop shy of telling me enough to get it working.
What I'm trying to do is make a simple rhythm game where the player taps a button at regular intervals (ie. beats). I wanted to set up a way of signalling when to tap by having the button change colour, and since this would be a repeated task at regular intervals I want to use a timer object with a schedule method.
But when I try calling on this method it tells me that I can't change the UI in a non UI thread. I've tried a few ways to write a method in the main thread that I can call from the timer object but I get the same error every time. I'm assuming that I just have the wrong idea about what counts as being from the UI thread, so I was hoping someone could clear it up.
Here's a snippet of one way I tried it, just to show what my code looks like:
OnClickListener clickButton = new View.OnClickListener() {
public void onClick(View v) {
if (startBeat == 0){
startBeat = System.nanoTime();
timerStart.scheduleAtFixedRate((new TimerTask()
{
public void run()
{
flashButton();
}
}), 0, beatTime);
timerEnd.schedule(new TimerTask()
{
public void run()
{
unflashButton();
}
}, beatTolerance*2, beatTime);
return;
}
};
public void flashButton(){
beatPrompt.setBackgroundColor(getResources().getColor(R.color.primary1transparent_very));
}
public void unflashButton(){
beatPrompt.setBackgroundColor(getResources().getColor(R.color.primary1));
}
To be clear, this is all contained within my MainActivity class along with the OnCreate class.
if you are in an activity all you need to do is use runOnUiThread() and then place the code to change the ui element in there
public void flashButton(){
runOnUiThread(new Runnable() {
#Override
public void run() {
beatPrompt.setBackgroundColor(getResources().getColor(R.color.primary1transparent_very));
}
});
}
You cannot, under any circumstances, touch a UI object from a non UI thread.
You can accomplish your intent using Handler.sendMessageDelayed
UI can only be touched by the main thread. You should post the actions you are performing on the ui thread via handler or via runOnUiThread
Try something similar to this
timerStart.scheduleAtFixedRate((new TimerTask()
{
public void run()
{
//replace MainActivity with your activity
//if inside a fragment use getActivity()
MainActivity.this.runOnUiThread(new Runnable() {
public void run() {
flashButton();
}
});
}
}), 0, beatTime);
If you are in an Activity you could surround flashButton() with an runOnUiThread.
...
runOnUiThread(new Runnable(){
public void run(){
flashButton();
}
});
...
use android.os.Handler Class. Change your code as follows:
private Handler handler=new Handler();
public void flashButton(){
handler.post(new Runnable(){
public void run(){
beatPrompt.setBackgroundColor(getResources().getColor(R.color.primary1transparent_very));
}
});
}
public void unflashButton(){
handler.post(new Runnable(){
public void run(){
beatPrompt.setBackgroundColor(getResources().getColor(R.color.primary1));
}
});
}
Related
Currently in my Android Game there is a simple thread that runs, decreasing a horizontal progressbar by 1 every X milliseconds. I'm trying to implement a method so when the progressbar hits 0, a TextView changes to "Game Over". The app crashes whenever this function is called in this way. I have also initialized the variable correctly so the method should have no trouble seeing this TextView.
public class MyThread extends Thread{
#Override
public void run(){
while (counter > 0 && keepRunning){
counter = counter - 1;
android.os.SystemClock.sleep(calculateSleepTick());
mHandler.post(new Runnable() {
#Override
public void run() {
progressTest.setProgress(counter);
}
});
}
isGameOver();
}
}
public void isGameOver(){
scoreText.setText("Game Over");
}
Your isGameOver function sets the text of a UI element. You can't call functions of UI elements on a thread other than main. It needs to be posted to the UI thread to do that.
You cannot update UI in non UI threads. Call isGameOver() this way.
runOnUiThread(new Runnable() {
#Override
public void run() {
isGameOver();
}
});
I've got game based on CountDownTimer, which is continuously repeating countdowns. This countDown is counting time for user to react on some action related to number, if user reacts onFinish() is called by some clickListener or by itself if the time was up. Depending of succesCondition(), method success or fail is called and those methods are defining if game is still running.
OnCreate
loop = gameLoop(time).start();
MainActivity
public CountDownTimer gameLoop(int time){
return new CountDownTimer(time, time+100) {
#Override
public void onTick(long millisUntilFinished) {
}
#Override
public void onFinish() {
if (!Conditions.succesCondition(number)) {
success();
} else {
fail();
}
}
};
}
public void success() {
loop.cancel();
scoreCount++;
animation.start();
}
public void fail(){
loop.cancel();
}
However this timer runs on Main thread and that provides well known issue skipped xx frames, your app might be doing too much work on its main thread and I found that this is common issue for CountDownTimer and replacing it with Handler is a solution.
I can't put this timer in AsyncTask because it performs mainly UI related tasks (TextViews, TextSwitcher, some progressBar etc. in success() method. I didn't put that in code in those methods for more clean view of the main problem. I'm trying to reconstruct CountDownTimer- like concept with handler and runnable to replace my Timer, but I'm actually stuck with nothing. As you can see I'm using only onFinish method, onTick is not necessary.
I suggest using a combination of java.util.Timer, java.util.TimerTask and Activity.runOnUiThread(). First create a Timer and call one of its schedule...()methods. Any action that needs to be done on the main (ui) thread can be wrapped in runOnUiThread(() -> { ...}). Be sure to call cancel() on TimerTask and Timer if those objects are no longer needed. Cancelling the Timer cancels the TimerTask as well.
Here is how this may look like:
public class TimerTaskActivity extends Activity {
Timer timer;
TimerTask timerTask;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.timertask);
...
}
#Override
protected void onStart() {
super.onStart();
timer = new Timer();
timerTask = new TimerTask() {
#Override
public void run() {
runOnUiThread(() -> {
....
});
}
};
timer.scheduleAtFixedRate(timerTask, 2000, 2000);
}
#Override
protected void onPause() {
super.onPause();
timer.cancel();
}
}
You may handle this situation using AsyncTask as well overriding the onProgressUpdate method.
Here's an example about how you can achieve the behaviour to interact with your main thread from AsyncTask. The example shows the update of a download which can be easily transformed to your specific problem of timer.
Update
In my case almost all code would be in onProgressUpdate, would it
still make any sense?
No, your code will not be in onProgressUpdate. The onProgressUpdate method will only be updating your timer in your UI. As far as I could understand, the success and the fail will be triggered based on user action as well. Then those actions are triggered, you can stop the AsyncTask to update your timer as well. You just need to AsyncTask to update the timer value time to time.
You will get a callback in your Activity when the AsyncTask finishes. See the mNotificationHelper.completed(); function in the above example. When you are notified in your Activity when the timer finishes, you might then execute the following task there.
public void completed() {
if (!Conditions.succesCondition(number)) {
success();
} else {
fail();
}
}
OK. I finally figured out how to handle it with handler (hehe):
public void startGameAction() {
//My game actions
handler = new Handler();
runnable = () -> {
if (!Conditions.succesCondition(number)) {
success();
} else {
fail();
}
};
handler.postDelayed(runnable,time);
}
public void success(){
handler.removeCallbacks(runnable);
handler = null;
scoreCount++;
//other stuff
startGameAction();
}
private void fail() {
handler.removeCallbacks(runnable);
//other stuff
}
onCreate only startGame call, handler and runnable defined as class fields
startGameAction();
I have a thread that will do some processing, then has runnable code which will display the results on the screen. The issue is that if the user presses the back arrow while the runnable is between two lines of display code, the next line will crash as the activity no longer exists.
The below code accomplishes the goal, but I hate having if statements before each line. Is there a better way?
#Override
public void onBackPressed() {
super.onBackPressed();
imgThread.interrupt();
}
private void processImage(){
final Handler mHandler = new Handler(Looper.getMainLooper());
progress = new ProgressDialog(this);
progress.setMessage("TEXT");
progress.setIndeterminate(true);
progress.setProgressStyle(ProgressDialog.STYLE_SPINNER);
progress.show();
imgThread = new Thread(){
#Override
public void run() {
//Process the image a bit
mHandler.post(new Runnable() {
#Override
public void run() {
if(!imgThread.isInterrupted())
imageView.setImageBitmap(mDisplayBitmap);
if(!imgThread.isInterrupted())
progress.setMessage("TEXT TEXT");
if(!imgThread.isInterrupted())
progress.show();
}
});
//More processing
mHandler.post(new Runnable() {
#Override
public void run() {
if(!imgThread.isInterrupted())
addScreenListener();
if(!imgThread.isInterrupted())
determineHelpToast("TEXT TEXT TEXT", Toast.LENGTH_LONG);
if(!imgThread.isInterrupted())
progress.dismiss();
}
});
}
}; imgThread.start();
}
The really safe way to do this is to modify your Runnable so that it never references the Android Context (Activity, etc.).
The easiest way to do this is to communicate changes to the Activity via an event bus.
My problem is pretty simple. I am creating a card based on the result of a HTTP query performed inside a separate thread. The card also has an onclick method and is defined inside a runOnUiThread() located inside the separate thread. However, when the device is tapped, the onclick event isn't fired.
Here is my code:
private void login() {
Runnable r = new Runnable() {
#Override
public void run() {
// irrelevant code
runOnUiThread(new Runnable() {
#Override
public void run() {
setContentView(buildError(code));
}
}
}
Thread t = new Thread(r);
t.start();
}
private View buildError(String code) {
CardBuilder card = new CardBuilder(this, CardBuilder.Layout.ALERT);
card.setIcon(R.drawable.ic_warning_150);
if (code.equals("1"))
card.setText("Incorrect credientals");
else
card.setText("Unexpected error");
card.setFootnote("Tap to try again");
View cView = card.getView();
cView.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Log.i("Event", "Clicked"); // This is what isn't triggering
}
});
cView.setFocusable(true);
cView.setFocusableInTouchMode(true);
return cView;
}
Even though the snippet of code contains an error (can't be compiled, missing ; at the Runnable statement), you were on the right track.
The View simply needs to request the focus in order to be clickable right away. Otherwise you'll have to move the focus manually.
cView.setFocusable(true);
cView.setFocusableInTouchMode(true);
cView.requestFocus();
Reference
So I have some simple code but it seems to not be working.. any suggestions?
I just want an image to show after a button is pressed then become invisible after 2 seconds.
button.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
firstImage.setVisibility(ImageView.VISIBLE);
// delay of some sort
firstImage.setVisibility(ImageView.INVISIBLE);
}
}
The image never shows, it always stays invisible, should I be implementing this in another way? I've tried handlers.. but it didn't work, unless I did it wrong.
Never make your UI thread sleep!
Do this:
final Handler handler = new Handler();
button.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
firstImage.setVisibility(ImageView.VISIBLE);
handler.postDelayed(new Runnable(){
public void run(){
firstImage.setVisibility(ImageView.INVISIBLE);
}
}, DELAY);
}
}
Where you would set DELAY as 2000 (ms).
Well, you will need to add a delay between the two lines. Use a thread or a timer to do this.
Start a thread on click of a button. In the run method, change the ImageView's visibility to VISIBLE, then put the thread to sleep for n secs, and then change then make it invisible.
To call the imageView's setvisibility method, you will need a hanlder here.
Handler handler = new Handler();
handler.post(new Runnable() {
public void run() {
image.setVisibiliy(VISIBLE);
Thread.sleep(200);
image.setVisibility(INVISIBLE);
}
});
I know this question has already been answered, but I thought I would add an answer for people who like me, stumbled across this looking for a similar result where the delay was caused by a process rather than a "sleep"
button.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
firstImage.setVisibility(ImageView.VISIBLE);
// Run the operation on a new thread
new Thread(new Runnable(){
public void run(){
myMethod();
returnVisibility();
}
}).start();
}
}
private void myMethod() {
// Perform the operation you wish to do before restoring visibility
}
private void returnVisibility() {
// Restore visibility to the object being run on the main UI thread.
MainActivity.this.runOnUiThread(new Runnable() {
#Override
public void run() {
firstImage.setVisibility(ImageView.INVISIBLE);
}
});
}