I have a situation in an Android app where I want to start a network activity (sending out some data) which should run every second. I achieve this as follows:
In the onCreate() I have the code:
tv = new TextView(this);
tv.postDelayed(sendData, 1000);
The sendData() function:
Handler handler = new Handler();
private Runnable sendData=new Runnable(){
public void run(){
try {
//prepare and send the data here..
handler.removeCallbacks(sendData);
handler.postDelayed(sendData, 1000);
}
catch (Exception e) {
e.printStackTrace();
}
}
};
The problem come in like this: When user presses the back buttons and app comes out (UI disappears) the sendData() function still gets executed which is what I want. Now when user re-starts the app, my onCreate() gets called again and I get sendData() invoked twice a second. It goes on like that. Every time user comes out and starts again, one more sendData() per second happens.
What am I doing wrong? Is it my new Handler() creating problem? What is the best way to handle this? I want one sendData() call per second until user quits the app (form application manager).
final Handler handler = new Handler();
handler.postDelayed(new Runnable() {
#Override
public void run() {
//Do something after 100ms
Toast.makeText(c, "check", Toast.LENGTH_SHORT).show();
handler.postDelayed(this, 2000);
}
}, 1500);
Perhaps involve the activity's life-cycle methods to achieve this:
Handler handler = new Handler();
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
handler.post(sendData);
}
#Override
protected void onDestroy() {
super.onDestroy();
handler.removeCallbacks(sendData);
}
private final Runnable sendData = new Runnable(){
public void run(){
try {
//prepare and send the data here..
handler.postDelayed(this, 1000);
}
catch (Exception e) {
e.printStackTrace();
}
}
};
In this approach, if you press back-key on your activity or call finish();, it will also stop the postDelayed callings.
Why don't you create service and put logic in onCreate(). In this case even if you press back button service will keep on executing. and once you enter into application it will not call
onCreate() again. Rather it will call onStart()
You can simplify the code like this.
In Java:
new Handler().postDelayed (() -> {
//your code here
}, 1000);
In Kotlin:
Handler().postDelayed({
//your code here
}, 1000)
Please check the below its working on my side in below code your handler will run after every 1 Second when you are on same activity
HandlerThread handlerThread = new HandlerThread("HandlerThread");
handlerThread.start();
handler = new Handler(handlerThread.getLooper());
runnable = new Runnable()
{
#Override
public void run()
{
handler.postDelayed(this, 1000);
}
};
handler.postDelayed(runnable, 1000);
Handler h = new Handler() {
#Override
public void handleMessage(Message msg) {
super.handleMessage(msg);
if (msg.what==0){
// do stuff
h.removeMessages(0); // clear the handler for those messages with what = 0
h.sendEmptyMessageDelayed(0, 2000);
}
}
};
h.sendEmptyMessage(0);
I think you could experiment with different activity flags, as it sounds like multiple instances.
"singleTop"
"singleTask"
"singleInstance"
Are the ones I would try, they can be defined inside the manifest.
http://developer.android.com/guide/topics/manifest/activity-element.html
You should set andrid:allowRetainTaskState="true" to Launch Activity in Manifest.xml. If this Activty is not Launch Activity. you should set android:launchMode="singleTask" at this activity
Related
I want to change from my current activity to another while I am inside a Handler. The idea is other code inside the handler will run until a certain condition doesnt match (with increment of the count value every time). When the count value matches the condition I close the activity and move to another.
my code is:
mHandler = new Handler();
mRunnable = new Runnable() {
#Override
public void run() {
if(count<CONDITION_VALUE)
{
//do other stuff...
count++;
}else
{
//change activity...
finish();
}
mHandler.postDelayed(mRunnable, 4000);
}
};
mHandler.postDelayed(mRunnable, (1000));
The code is running without any error but the old activity is not being destroyed (i guess) and the new activity is reloaded after every 4 seconds.
I want the new activity to load only once.
How can I achieve this?
try this, from enter link description here
in your Activity
#Override
public void onDestroy() {
mHandler.removeCallbacks(mRunnable);
super.onDestroy();
}
I created one handler to repeat a task repeatedly and I also want to destroy it within that handler once a condition has been met.
pinHandler = new Handler();
Now I created two functions separately to start and stop the task.
void startRepeatingPins() {
mPinSetter.run();
}
Runnable mPinSetter = new Runnable() {
#Override
public void run() {
try{
System.out.println("PinIndwx count is :"+pinIndexCount);
if(pinIndexCount==(plist.size()-1))
{
stopUpdatingPins();
pinIndexCount=0;
//pinHandler.removeCallbacks(mPinSetter);
System.out.println("Handler stopped by itself.");
}
else
{
updatePoint(plist.get(pinIndexCount));
pinIndexCount++;
}
}
finally {
pinHandler.postDelayed(mPinSetter, pinInterval);
}
}
};
private void stopUpdatingPins()
{
pinIndexCount=0;
pinHandler.removeCallbacks(mPinSetter);
System.out.println("Called the stop function.");
}
Now, the issue is that, if I call the stopUpdatingPins function , the handler stops but when I try to stop it automatically from within the handler, it just doesn't stop. Although the stopUpdatingPins function does get called.
Change You startRepeatingPins() like this, You should not directly call the run. If your run like this then there is no point of removing this from Handler. So attach Runnable with Handler.
void startRepeatingPins() {
pinHandler.post(mPinSetter);
}
You added post delay in finally that means you are stopping at first if loop and starting again in finally, So it's never stopping. So Change your runnable like this,
Runnable mPinSetter = new Runnable() {
#Override
public void run() {
System.out.println("PinIndwx count is :"+pinIndexCount);
if(pinIndexCount==(plist.size()-1))
{
stopUpdatingPins();
pinIndexCount=0;
//pinHandler.removeCallbacks(mPinSetter);
System.out.println("Handler stopped by itself.");
}
else
{
updatePoint(plist.get(pinIndexCount));
pinIndexCount++;
pinHandler.postDelayed(mPinSetter, pinInterval);
}
}
};
What I want to do is just a basic implementation of handler example. I have a TextView on the mainActivity, and once the page loads the handler is supposed to run and show the user value coming from SystemClock.uptimeMillis. But ıt doesn't work more than once. How can I make this code run?
public class MainActivity extends Activity {
long uptoMS=0L;
TextView tv;
Handler handler=new Handler();
long swaptime=0L;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
tv=(TextView)findViewById(R.id.textView1);
uptoMS=SystemClock.uptimeMillis();
tv.setText(String.valueOf(uptoMS));
handler.post(runner);
}
private Runnable runner=new Runnable() {
#Override
public void run() {
// TODO Auto-generated method stub
swaptime+=uptoMS;
tv.setTag(String.valueOf(swaptime));
handler.post(this);
}
};
}
See this below example
scheduler(){
TimerTask tasknew = new TimerSchedulePeriod();
Timer timer = new Timer();
// scheduling the task at interval
timer.schedule(tasknew,100, 100);
}
// this method performs the task
public void run() {
System.out.println("timer working");
}
timer = new Timer();
refreshTask = new TimerTask() {
#Override
public void run() {
swaptime+=uptoMS;
tv.setTag(String.valueOf(swaptime));
handler.post(this);
}
};
timer.schedule(refreshTask,
100, 100);
Well, there some problems with your code.
Firstly, you use setTag() instead of setText(), so the value will never update.
tv.setTag(String.valueOf(swaptime));
Secondly, you get uptoMS once in onCreate(), and then you use it in every "handler loop". I don't know what you try to achive but it's unlike that you want this.
Thirdly, you instantly repost your Runnable, so the main thread's message queue will be busy. You should give some break instead of instant reposting. For example you can wait 100 ms between the updates, so the TextView will be updated 10 times in every second.
handler.postDelayed(this, 100);
And finally, however others suggest you using Timer, just ignore them. Handler is the Android way to achieve tasks like this.
I have a TextView. I want to update its text (append a "1") after 1 second of a button click.
public class HaikuDisplay extends Activity {
Method m;
Timer t;
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
t = new Timer();
m = HaikuDisplay.class.getMethod("change");
}
//Event handler of the button
public void onRefresh(View view)
{
//To have the reference of this inside the TimerTask
final HaikuDisplay hd = this;
TimerTask task1 = new TimerTask(){
public void run(){
/*
* I tried to update the text here but since this is not the UI thread, it does not allow to do so.
*/
//Calls change() method
m.invoke(hd, (Object[])null);
}
};
t.schedule(task1, 1000);
}
public void change()
{
//Appends a "1" to the TextView
TextView t = (TextView)findViewById(R.id.textView1);
t.setText(t.getText() + "1");
}
//Event handler of another button which updates the text directly by appending "2".
//This works fine unless I click the first button.
public void onRefresh1(View view)
{
TextView t = (TextView)findViewById(R.id.textView1);
t.setText(t.getText() + "2");
}
}
Consider all Exceptions be handled.
On first click, m.invoke gives InvocationTargetException. But it calls the method change() on successive invokes without any Exceptions(verified by logging). But it does not update the text. Where am I wrong?
Also, I see in the debugger that it creates a new Thread every time I click the button. That is fine. But why isn't it removing the previous Threads though their execution has been completed?
Do something like this
public void onRefresh1(View v) {
// You can have this in a field not to find it every time
final EditText t = (EditText) findViewById(R.id.textView1);
t.postDelayed(new Runnable() {
#Override
public void run() {
t.append("1");
}
}, 1000);
}
new Handler().postDelayed(new Runnable() {
#Override
public void run() {
// Update UI
}
}, 1000);
implement this on button click
UPDATE:
There are some other answers. dtmilano suggested another solution which is almost same to mine except he is calling the postDelayed method of View class and In my answer I used postDelayed method of handler class.
from the api reference of android the postDelayed method of Handler says
The runnable will be run on the thread to which this handler is
attached.
and the postDelayed method of View says
The runnable will be run on the user interface thread.
This is the only difference between these two solution. in my answer instead of creating new Handler every time you can use any other handler instance. Then the runnable will be run on that thread where that specific handler is declared. And if the postDelayed of EditText is used the the runnable method will be run on the user Interface Thread.
Now the performance issue, both has the same performance (If anybody can prove me wrong with reference I will be happy)
That's looking awful convoluted - have you considered using CountDownTimer instead?
new CountDownTimer(1000, 1000) {
public void onTick(long millisUntilFinished) {
// no-op
}
public void onFinish() {
change();
}
}.start();
This should call change (and hence change the text) on the UI thread, avoiding reflection and threading errors.
Hi Use the following code for that. Hope this will help you .
new java.util.Timer().schedule(
new java.util.TimerTask() {
#Override
public void run() {
// your code here
}
},
1000
);
Have a look of this question also.
display data after every 10 seconds in Android
You can try with this also.
private Handler handler = new Handler();
private Runnable runnable = new Runnable() {
public void run() {
doStuff();
/*
* Now register it for running next time
*/
handler.postDelayed(this, 1000);
}
};
**EDIT 3**
Try with this once you are need to enable once (i mean if you put your code in yourmethod()== this will get automatically call 1 seconds once.
private Timer timer;
TimerTask refresher;
// Initialization code in onCreate or similar:
timer = new Timer();
refresher = new TimerTask() {
public void run() {
yourmethod();
};
};
// first event immediately, following after 1 seconds each
timer.scheduleAtFixedRate(refresher, 0,100);
After pushing a button, i want to close an activity. But, I’d like to wait some seconds before closing it, because users have to read a short message displayed on that activity.
I tried using Thread inside the onClick event
try{
Thread.sleep(2000);
finish();
}
catch(Exception e){}
But, when I push the button, the entire objects are freeze (for example, the button stay pushed).
Then I used a simple Timer
timer.schedule(task(), 2000);
And it seems to work well. Is it correct to use a Timer in this situation, or should I use a Thread or something else?
new Handler().postDelayed(new Runnable() {
#Override
public void run() {
Activity.this.finish();
}
}, 2000) ;
The easiest way is probably to use a Handler
private Handler h = new Handler();
...
h.postDelayed(new Runnable() {
#Override
public void run() {
finish();
}
}, 2000);