I'm new to android and I want to do a simple example where I click on a start button and another Activity is open, there a simple number starting in one and counting upwards, but I'm facing a problem, after I initialize some variables on onCreate method (In the second activity), where should I actually start the while statement to count and modify the text view?.
I wrote this class:
public class Counter extends Thread{
private TextView tv;
private int i;
public Counter( TextView tv ){
this.tv = tv;
}
#Override
public void run() {
while( true ){
tv.setText(i);
try {
sleep(500);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
i++;
}
}
And started the thread over here:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_game);
counter = new Counter( (TextView) findViewById(R.id.textView2) );
counter.start( );
}
#SuppressLint("UseValueOf")
final Handler handler = new Handler();
handler.post(new Runnable() {
#Override
public void run() {
// change your text here
if (condition) {
i++;
txt_TimeRecord.setText("" + i);
} else {
i = 0;
}
handler.postDelayed(this, 1 * 1000L);
}
});
[Formatted the code properly]
//In first activity
//set onclick method to that button.
public void onclick(view v)
{
Intent intent = new Intent(this, secondactivity.class);
startActivity(intent);
}
// in second activity in
// initi i value.
while(i<10)
{
i++ ;
// sleep statement
//print that i in textview
}
I've found what I need from a similar post, the handler was needed since only the UI Thread can update the user interface.
private void countNumbers() {
final TextView numbers = (TextView) findViewById(R.id.textView2);
final Handler handler = new Handler();
Runnable runnable = new Runnable() {
public void run() {
int i = 0;
while (i++ < 500) {
try {
Thread.sleep(10);
}
catch (InterruptedException e) {
e.printStackTrace();
}
final int j = i;
handler.post(new Runnable(){
public void run() {
numbers.setText(Integer.toString(j));
}
});
}
}
};
new Thread(runnable).start();
}
The method countNumbers() is called in onCreate().
Related
I want to send a character with Bluetooth. The code works perfectly when there is only a single character.But I want to use a delay function between the two codes.
I want to enter any number with EditText and the app will take that number and do EditText/44. That is what I want to wait between 2 codes
Finally work.. Thanks guys. :)
I moved a,b,c inside setOnClick.. ;
kileri = (Button) findViewById(R.id.kileri);
final EditText value1 = (EditText) findViewById(R.id.textkont);
assert value1 != null;
value1.setText("0");
btAdapter = BluetoothAdapter.getDefaultAdapter();
checkBTState();
kileri.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
int a = Integer.parseInt(value1.getText().toString());
int b = a / 44;
int c = b * 1000;
sendData("F");
try {
Thread.sleep(c);
} catch (Exception e) {
e.printStackTrace();
}
You can use handler
new Handler().postDelayed(new Runnable() {
#Override
public void run() {
//do something
}
}, 2000 );//time in milisecond
try {
//set time in mili
Thread.sleep(3000);
}catch (Exception e){
e.printStackTrace();
}
edited as your code
kileri.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
sendData("F");
try {
//set time in mili
Thread.sleep(3000);
}catch (Exception e){
e.printStackTrace();
}
sendData("S");
}
});
Use handler like this:
new Handler().postDelayed(new Runnable() {
#Override
public void run() {
// do something after 2s = 2000 miliseconds
}
}, 2000); //Time in milisecond
You can do like this
kileri = (Button) findViewById(R.id.kileri);
final EditText value1 = (EditText) findViewById(R.id.textkont);
assert value1 != null;
value1.setText("0");
final int a = Integer.parseInt(value1.getText().toString());
final int b = a/22;
final int c = b/2; // It will take a int from Edittext and do this operation on that.
btAdapter = BluetoothAdapter.getDefaultAdapter();
checkBTState();
kileri.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
sendData("F");
new Handler().postDelayed(new Runnable() {
#Override
public void run() {
sendData("S");
}
}, c);
}
});
just use runOnUiThread on button click and post Handler after time delay..
Button button = new Button(this);
button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
sendData("F"); // send
delay(2000);
}
});
UPDATE
delay()..
public void delay(final int c){
runOnUiThread(new Runnable() {
#Override
public void run() {
try {
Thread.sleep(c);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
});
new Handler().postDelayed(new Runnable() {
#Override
public void run() {
sendData("S"); //send
}
}, c);
}
It's not recommended to use Thread.Sleep because it stops execution of main thread if it is called in main thread execution.So,if we want to set delay we can use CountDownTimer.
In below snippet,we gave 2 seconds delay.So,after 2s onFinish() callback comes and we can have our operation there.
new CountDownTimer(2000, 1000) {
public void onFinish() {
}
public void onTick(long millisUntilFinished) {
}.start();
}
Can anyone explain when I put the thread to sleep for 30 milliseconds it updates the UI from the background thread. but when I put the sleep for 300 milliseconds it crashes saying that you cannot touch view from another thread. I expect it to crash in both cases but somehow it is working in 30 milliseconds. Needs some clarification on this issue.
public class HandlerDemo extends Activity implements Handler.Callback{
private static final String TAG = "FFFF";
private Handler mHandler = null;
private Handler mUIHandler = null;
private HandlerThread backgroundThread = null;
public static final int BACKGROUND_OPERATION = 10;
public static final int MAIN_THREAD_OPERATION = 20;
private TextView asd;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
HandlerThread backgroundThread = new HandlerThread("BACKGROUND_THREAD");
backgroundThread.start();
mHandler = new Handler(backgroundThread.getLooper(), this);
mHandler.sendEmptyMessage(BACKGROUND_OPERATION);
// mUIHandler = new Handler(Looper.getMainLooper(), this);
// mUIHandler.sendEmptyMessage(MAIN_THREAD_OPERATION);
}
#Override
protected void onDestroy() {
super.onDestroy();
mHandler.getLooper().quit();
}
#Override
public boolean handleMessage(Message message) {
Log.d(TAG, Thread.currentThread() + "");
switch (message.what) {
case MAIN_THREAD_OPERATION:
try {
Thread.sleep(30000);
} catch (InterruptedException e) {
e.printStackTrace();
}
((TextView) findViewById(R.id.textview)).setText("Updating from UI Handler");
findViewById(R.id.textview).invalidate();
break;
case BACKGROUND_OPERATION:
try {
**Thread.sleep(300);**
} catch (InterruptedException e) {
e.printStackTrace();
}
((TextView) findViewById(R.id.textview)).setText("Updating from background Handler");
findViewById(R.id.textview).invalidate();
break;
default:
break;
}
// message.recycle();
return true;
}
}
runOnUiThread(new Runnable() {
#Override
public void run() {
// do what you want
}
});
In my application I have a button and when it gets clicked I start a new thread and change the text of button. If I press the button again it will start changing its text faster.
I would like to interrupt the thread when the button is pressed in the second time. What's the correct way to do it?
public class TestActivity extends Activity {
Button btn;
int i = 0;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
btn = (Button)findViewById(R.id.btn);
btn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
runThread();
}
});
}
private void runThread() {
new Thread() {
public void run() {
while (i++ < 1000) {
try {
runOnUiThread(new Runnable() {
#Override
public void run() {
btn.setText("#" + i);
}
});
Thread.sleep(300);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}.start();
}
In this case, just keep a reference to your thread and use Thread.interrupt():
private Thread runThread() {
return new Thread() {
public void run() {
while (i++ < 1000) {
try {
runOnUiThread(new Runnable() {
#Override
public void run() {
btn.setText("#" + i);
}
});
Thread.sleep(300);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
Then:
btn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
if (myThread != null) myThread.interrupt();
myThread = runThread();
myThread.start();
}
});
Read this post for more info and options:
How to properly stop the Thread in Java?
In my opinion, the best way would be using a variable to control this.
Something like:
while(i++ < 1000 && keepRunning)
I see that as a good solution because it cant cause unexpected behavior, as you are sure the exactly moment your thread would exit.
extra--
As a suggestion, I also would recommend you to set your thread non-Damon (setDaemon(false)) because it makes layout changes
Also it is a good practice to give thread a name (setName()) to make it easy on debugging.
Right now you start a new Thread each time you press the button.
Something like this should work.
public class TestActivity extends Activity {
Button btn;
int i = 0;
Thread countThread = null;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
countThread = new Thread() {
public void run() {
while (i++ < 1000) {
try {
runOnUiThread(new Runnable() {
#Override
public void run() {
btn.setText("#" + i);
}
});
Thread.sleep(300);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
btn = (Button)findViewById(R.id.btn);
btn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
runThread();
}
});
}
private void runThread() {
if(countThread != null) {
if(countThread.isAlive()) {
countThread.stop();
} else {
countThread.start();
}
}
}
I only had a text editor so I can't guarantee if this solves your problem.
You can use thread.interrupt() to interrupt the thread.
Try this, Just take another variable j and it will handle your code:-
public class TestActivity extends Activity {
Button btn;
int i = 0,j=0;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
btn = (Button)findViewById(R.id.btn);
btn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
j=1;
runThread();
}
});
}
private void runThread() {
new Thread() {
public void run() {
while (i++ < 1000) {
try {
runOnUiThread(new Runnable() {
#Override
public void run() {
if(j==1){
btn.setText("#" + i);
j=0;
}
else
Thread.interrupted();
}
});
Thread.sleep(300);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}.start();
}
You can use normal Thread in Android (and call interrupt() for your use case) but frameworks provides other better options by providing helper classes around Threads. You can refer to official documentation page for other options.
HandlerThread is preferred option. You can call quitSafely() or quit() for your use case if you go for HandlerThread
Related post:
Why use HandlerThread in Android
I get this error "Can't create handler inside thread that has not called Looper.prepare()"
Can you tell me how to fix it?
public class PaymentActivity extends BaseActivity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.payment);
final Button buttonBank = (Button) findViewById(R.id.buttonBank);
buttonBank.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
progressDialog = ProgressDialog.show(PaymentActivity.this, "",
"Redirecting to payment gateway...", true, true);
new Thread() {
public void run() {
try {
startPayment("Bank");
} catch (Exception e) {
alertDialog.setMessage(e.getMessage());
handler.sendEmptyMessage(1);
progressDialog.cancel();
}
}
}.start();
}
});
StartPayment Method:
private void startPayment(String id) {
Bundle b = getIntent().getExtras();
final Sail sail = b.getParcelable(Constant.SAIL);
final Intent bankIntent = new Intent(this, BankActivity.class);
try {
Reservation reservation = RestService.createReservation(
sail.getId(),
getSharedPreferences(Constant.PREF_NAME_CONTACT, 0));
bankIntent.putExtra(Constant.RESERVATION, reservation);
// <workingWithDB> Storing Reservation info in Database
DBAdapter db = new DBAdapter(this);
db.open();
#SuppressWarnings("unused")
long rowid;
rowid = db.insertRow(sail.getId(), sail.getFrom(),
sail.getTo(), sail.getShip(), sail.getDateFrom().getTime(),
sail.getPrice().toString(), reservation.getId().floatValue());
db.close();
// </workingWithDB>
String html = PaymentService.getRedirectHTML(id, reservation);
bankIntent.putExtra(Constant.BANK, html);
} catch (Exception e) {
AlertDialog.Builder builder = new AlertDialog.Builder(this);
AlertDialog alertDialog = builder.create();
alertDialog.setMessage(e.getMessage());
alertDialog.show();
}
startActivity(bankIntent);
}
You should know that when you try to modify your UI , the only thread who can do that is the UiThread.
So if you want to modify your UI in another thread, try to use the method: Activity.runOnUiThread(new Runnable);
Your code should be like this :
new Thread() {
public void run() {
YourActivity.this.runOnUiThread(new Runnable(){
#Override
public void run(){
try {
startPayment("Bank");//Edit,integrate this on the runOnUiThread
} catch (Exception e) {
alertDialog.setMessage(e.getMessage());
handler.sendEmptyMessage(1);
progressDialog.cancel();
}
});
}
}
}.start();
I assume you create a Handler in startPayment() method. You can't do that, as handlers can be created on th UI thread only. Just create it in your activity class.
Instead of new Thread() line, try giving
this.runOnUiThread(new Runnable() {
you cant change any UI in thread you can use runOnUIThread or AsyncTask for more detail about this click here
I've found that most thread handling can be replaced by AsyncTasks like this:
public class TestStuff extends Activity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Button buttonBank = (Button) findViewById(R.id.button);
buttonBank.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
new StartPaymentAsyncTask(TestStuff.this).execute((Void []) null);
}
});
}
private class StartPaymentAsyncTask extends AsyncTask<Void, Void, String> {
private ProgressDialog dialog;
private final Context context;
public StartPaymentAsyncTask(Context context) {
this.context = context;
}
#Override
protected void onPreExecute() {
dialog = new ProgressDialog(context);
// setup your dialog here
dialog.setProgressStyle(ProgressDialog.STYLE_SPINNER);
dialog.setMessage(context.getString(R.string.doing_db_work));
dialog.setCancelable(false);
dialog.show();
}
#Override
protected String doInBackground(Void... ignored) {
String returnMessage = null;
try {
startPayment("Bank");
} catch (Exception e) {
returnMessage = e.getMessage();
}
return returnMessage;
}
#Override
protected void onPostExecute(String message) {
dialog.dismiss();
if (message != null) {
// process the error (show alert etc)
Log.e("StartPaymentAsyncTask", String.format("I received an error: %s", message));
} else {
Log.i("StartPaymentAsyncTask", "No problems");
}
}
}
public void startPayment(String string) throws Exception {
SystemClock.sleep(2000); // pause for 2 seconds for dialog
Log.i("PaymentStuff", "I am pretending to do some work");
throw new Exception("Oh dear, database error");
}
}
I pass in the Application Context to the Async so it can create dialogs from it.
The advantage of doing it this way is you know exactly which methods are run in your UI and which are in a separate background thread. Your main UI thread isn't delayed, and the separation into small async tasks is quite nice.
The code assumes your startPayment() method does nothing with the UI, and if it does, move it into the onPostExecute of the AsyncTask so it's done in the UI thread.
Try
final Handler handlerTimer = new Handler(Looper.getMainLooper());
handlerTimer.postDelayed(new Runnable() {
public void run() {
......
}
}, time_interval});
I am trying to update a textview after 3 seconds, and i want to do that in a loop for which i am using thread .....what should i do in order to start background thread so that exactly after 3 seconds background1 thread starts ... and it should be done in a loop ?
package com.edu.math;
import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.util.Log;
import android.widget.TextView;
public class EduMath extends Activity {
TextView txt;
TextView tv;
TextView num;
String x;
int time = 3000;
float z ;
int random;
int random1;
int random_operator =1;
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
txt=(TextView)findViewById(R.id.txt);
tv = (TextView)findViewById(R.id.randomNumber);
background.start();
}
// our handler
Handler handler = new Handler() {
public void handleMessage(Message msg) {//display each item in a single line
random = (int)Math.ceil(Math.random()*10);
random1 = (int)Math.ceil(Math.random()*10);
if(random1>random)
{
txt.setText(/*txt.getText()+*/""+random1+" "+>+" "+random+" "+
System.getProperty("line.separator"));
}
else
{
txt.setText(/*txt.getText()+*/""+random+" "+>+" "+random1+
System.getProperty("line.separator"));
}
}
};
Handler handler1 = new Handler() {
#Override
public void handleMessage(Message msg) {//display each item in a single line
txt.setText(/*txt.getText()+*/""+random1+" "+x+" "+random+System.getProperty("line.separator"));
}
};
Thread background1 =new Thread(new Runnable() {
#Override
public void run() {
for(int i=0;i<10;i++)
{
try {
Thread.sleep(time);
// send message to the handler with the current message handler
handler1.sendMessage(handler1.obtainMessage());
background.stop();
Log.d("EduMath-enclosing_method", "thread started");
} catch (Exception e) {
Log.v("Error", e.toString());
}
}
}
});
Thread background=new Thread(new Runnable() {
#Override
public void run() {
for(int i=0;i<10;i++)
{
try {
Thread.sleep(time);
// send message to the handler with the current message handler
handler.sendMessage(handler.obtainMessage());
background1.start();
} catch (Exception e) {
Log.v("Error", e.toString());
}
}
}
});
}
You must use AsyncTask for changing any views in layout, but at now I have very little experience with AsyncTask.
Try to use a java.util.Timer ( http://download.oracle.com/javase/1.4.2/docs/api/java/util/Timer.html )
public class HandlerDemo extends Activity {
ProgressBar bar;
Handler handler=new Handler() {
#Override
public void handleMessage(Message msg) {
//add your text
}
};
AtomicBoolean isRunning=new AtomicBoolean(false);
public void onStart() {
super.onStart();
Thread background=new Thread(new Runnable() {
public void run() {
try {
Thread.sleep(3000);
handler.sendMessage(handler.obtainMessage());
}
catch (Throwable t) {
// just end the background thread
}
}
});
isRunning.set(true);
background.start();
}
public void onStop() {
super.onStop();
isRunning.set(false);
}
}
Try the solution on this post...seems to be what you looking for http://androidgenuine.com/?p=707