Develop Reference

OutOfMemory Exception in Android-Java. Allocation failed due to fragmentation

So I developed an Android application which acts as a server for my Android game(two separated apps), both applications were written in Java.
Previously I got messages on the Log like: "Skipped 2000 frames. The main thread could be overworking".
This is the code of my app, it's made of only the MainActivity:
I tried to introduce concurrent Threads in order to make the main thread lighter. Now the skipped n frames message isn't showed anymore but messages such like the followings are shown anyways.
"Alloc concurrent copying GC freed", "Starting a blocking GC alloc", "Waiting for a blocking GC alloc", "WaitForGcToComplete blocked alloc on HeapTrim" and all of this ends with
Throwing OutOfMemoryError "Failed to allocate a 32 byte allocation with 15604408 free bytes and 14MB until OOM, target footprint 268435456, growth limit 268435456; failed due to fragmentation (largest possible contiguous allocation 0 bytes)" (VmSize 5539048 kB).
I tried to deallocate some objects (lines of code which contains "x = null") but it didn't solve. Furthermore I checked with a log if there is some sort of endless loop but it doesn't seem to be the case.
public class MainActivity extends AppCompatActivity {
private static ActivityMainBinding binding;
private WSocServer server;
private int port = 8080;
private boolean isOnline = false;
private static ArrayList<String> logs = new ArrayList<>();
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
binding = ActivityMainBinding.inflate(getLayoutInflater());
setContentView(binding.getRoot());
setSupportActionBar(binding.toolbar);
binding.openConnection.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
if(!isOnline) {
isOnline = true;
server = new WSocServer(port);
server.start();
Toast toast = Toast.makeText(view.getContext(),"Server is on", Toast.LENGTH_LONG);
toast.show();
Log.i("WebSocket Server", "Started on port " + server.getPort());
}
else{
Snackbar snack = Snackbar.make(view ,"We are already online!", Snackbar.LENGTH_INDEFINITE);
snack.setAction("Got it", new View.OnClickListener() {
#Override
public void onClick(View view) {
snack.dismiss();
}
});
snack.show();
}
}
});
binding.closeConnection.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
if(isOnline) {
isOnline = false;
logs.clear();
Toast toast = Toast.makeText(view.getContext(),"Server is off", Toast.LENGTH_LONG);
toast.show();
try {
server.stop();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
else{
Snackbar snack = Snackbar.make(view ,"We are already offline!", Snackbar.LENGTH_INDEFINITE);
snack.setAction("Got it", new View.OnClickListener() {
#Override
public void onClick(View view) {
snack.dismiss();
}
});
snack.show();
}
}
});
}
private static void addOnView(){
ConstraintLayout cl = binding.logsView;
Handler h = new Handler(Looper.getMainLooper());
for(int i = 0; i < logs.size(); i++){
TextView tv = new TextView(binding.getRoot().getContext());
tv.setTextSize(16);
tv.setTextAlignment(View.TEXT_ALIGNMENT_CENTER);
tv.setPadding(40,180*(i+1),40,0);
tv.setText(logs.get(i));
Runnable r = new Runnable() {
#Override
public void run() {
cl.addView(tv);
}
};
h.post(r);
}
}
#Override
protected void onDestroy() {
super.onDestroy();
try {
server.stop();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
public static class WSocServer extends WebSocketServer {
private List<String> matchUsers;
private Integer timerSeconds;
private UUID matchId;
//a key represents a match to which an array of extracted numbers is associated
private Hashtable<String,Integer[]> matchExtractedNumbers = new Hashtable<>();
private Hashtable<String, Collection<WebSocket>> matchClients = new Hashtable<>();
private Hashtable<String,Hashtable<String,ArrayList<String>>> users_scorePerMatch = new Hashtable<>();
private Hashtable<String,WebSocket> clientConnection = new Hashtable<>();
private void initTimer(){
timerSeconds = 60;
Timer timer = new Timer();
TimerTask task = new TimerTask() {
public void run() {
if(timerSeconds > 0) timerSeconds--;
else {
timerSeconds = 60; timer.cancel(); timer.purge();
}
}
};
timer.schedule(task,0L,1000L);
}
private String UsersListToString(List list){
return list.toString().replace("[","").replace("]","");
}
private Integer[] generateExtractedNumbers(){
Integer[] callerBoard = new Integer[90];
List<Integer> boardPool = new ArrayList<>();
boardPool.addAll(Arrays.asList(IntStream.rangeClosed(1,90).boxed().toArray(Integer[]::new)));
for(int i = 0; i < 90; i++){
int rng = ThreadLocalRandom.current().nextInt(0,90-i);
callerBoard[i] = boardPool.remove(rng);
}
return callerBoard;
}
private void initMatch(){
matchId = UUID.randomUUID();
Integer[] matchBoard = generateExtractedNumbers();
matchExtractedNumbers.put(matchId.toString(),matchBoard);
matchClients.put(matchId.toString(),clientConnection.values());
Hashtable<String,ArrayList<String>> matchData = new Hashtable<>();
for(String user: matchUsers) matchData.put(user,new ArrayList<>());
users_scorePerMatch.put(matchId.toString(), matchData);
}
private Integer getExtractedNumber(String match, Integer turn){
if(turn >= 90) return -1;
Integer[] thisMatchExtractedNumbers = matchExtractedNumbers.get(match);
Integer returning = thisMatchExtractedNumbers[turn];
thisMatchExtractedNumbers = null;
return returning;
}
public WSocServer(int port){
super(new InetSocketAddress(port));
}
public WSocServer(InetSocketAddress address) {
super(address);
}
#Override
public void onOpen(WebSocket conn, ClientHandshake handshake) {
Thread thread = new Thread(new Runnable() {
#Override
public void run() {
Log.i("WebSocket(open)", conn.getRemoteSocketAddress().getAddress().getHostAddress() + " entered the room!");
logs.add(conn.getRemoteSocketAddress().getAddress().getHostAddress() + " entered the room!");
matchUsers = new ArrayList<>();
matchUsers.addAll(Arrays.asList("user1","user2","user3","user4","user5"));
}
});
thread.start();
}
#Override
public void onClose(WebSocket conn, int code, String reason, boolean remote) {
Thread thread = new Thread(new Runnable() {
#Override
public void run() {
Log.i("WebSocket(close)", conn + " has left the room! Reason: " + reason);
logs.add(conn + " has left the room!");
}
});
thread.start();
}
#Override
public void onMessage(WebSocket conn, String message) {
Thread thread = new Thread(new Runnable() {
#Override
public void run() {
logs.add(message + " from " + conn.getRemoteSocketAddress().getAddress().getHostAddress());
Log.i("WebSocket(message)", conn + ": " + message);
MainActivity.addOnView();
if(message.startsWith("username")){
if(matchUsers.size() < 6){
String user = message.replace("username;","");
if(!matchUsers.contains(user)) {
matchUsers.add(user);
clientConnection.put(user,conn);
}
String sending = "matchUsers;" + UsersListToString(matchUsers);
conn.send(sending);
}
else conn.send("errorUsername");
}
else if(message.equals("timerStart")){
initTimer();
if(matchUsers.size() < 6){
String sending = "timeStarter;" + timerSeconds.toString();
conn.send(sending);
}
else conn.send("errorTimer");
}
else if(message.equals("getMatchId")){
if(!matchUsers.isEmpty()){
initMatch();
matchUsers.clear();
}
String sending = "matchId;" + matchId.toString();
conn.send(sending);
}
else if(message.startsWith("inGame")){
String[] fields = message.split(";");
String matchId = fields[1].split("=")[1];
int turn = Integer.parseInt(fields[2].split("=")[1]);
Integer extraction = getExtractedNumber(matchId,turn);
fields = null;
conn.send("extracted=" + extraction.toString());
}
else if(message.startsWith("score")){
String matchId = message.split(";")[1].split("=")[1];
String score = message.split(";")[0].split("=")[1];
WebSocket[] clients = matchClients.get(matchId).toArray(new WebSocket[0]);
String user = "";
Enumeration<String> keys = clientConnection.keys();
String key = keys.nextElement();
while(!key.isEmpty()){
if(clientConnection.get(key) == conn) {
user = key;
break;
}
key = keys.nextElement();
}
keys = null;
Hashtable<String,ArrayList<String>> tmp = users_scorePerMatch.get(matchId);
ArrayList<String> tmp_list = tmp.get(user);
tmp_list.add(score);
tmp.replace(user,tmp_list);
users_scorePerMatch.replace(matchId,tmp);
for(int i = 0; i < clients.length; i++){
clients[i].send("statement;" + user + " got " + score + " with");
}
clients = null;
}
else if(message.startsWith("endMatchData")){
String matchId = message.split(";")[1].split("=")[1];
Hashtable<String,ArrayList<String>> users_ofMatch = users_scorePerMatch.get(matchId);
ArrayList<String> users = new ArrayList<>();
Enumeration<String> e = users_ofMatch.keys();
while(e.hasMoreElements()){
Log.e("endmatchdata","a");
users.add(e.nextElement());
}
e = null;
String sending = "matchEndData;";
for(String user: users) sending += user + "=" + UsersListToString(users_ofMatch.get(user)) + ":";
users_ofMatch = null;
conn.send(sending);
}
else if(message.startsWith("totalEnd")){
String matchId = message.split(";")[1].split("=")[1];
if(matchClients.get(matchId)!=null) {
WebSocket[] clients = matchClients.get(matchId).toArray(new WebSocket[0]);
for (WebSocket client : clients) client.close();
Enumeration<String> e = clientConnection.keys();
boolean exit = false;
while (e.hasMoreElements() && !exit) {
Log.e("totalend", "while");
for (WebSocket client : clients) {
Log.e("totalend", "for");
String tmp = e.nextElement();
if (clientConnection.get(tmp) == client) {
clientConnection.remove(tmp);
exit = true;
break;
}
}
}
e = null; clients = null;
matchClients.remove(matchId);
users_scorePerMatch.remove(matchId);
matchExtractedNumbers.remove(matchId);
}
}
}
});
thread.start();
}
#Override
public void onMessage(WebSocket conn, ByteBuffer message) {
Thread thread = new Thread(new Runnable() {
#Override
public void run() {
Log.i("WebSocket(message)", conn + ": " + message );
}
});
thread.start();
}
public static void main(String[] args){
}
#Override
public void onError(WebSocket conn, Exception ex) {
ex.printStackTrace();
}
#Override
public void onStart() {
Thread thread = new Thread(new Runnable() {
#Override
public void run() {
Log.i("WebSocket", "Server started!");
}
});
thread.start();
}
}
}
EDIT: The thing seems to be happening at the end of the match(i.e in the message.startsWith("totalEnd") or message.startsWith("endmatchdata") if cases in the onMessage method
EDIT 2: I found out that the addOnView function was badly written.
I changed it into
private static void addOnView(){
ConstraintLayout cl = binding.logsView;
Handler h = new Handler(Looper.getMainLooper());
final TextView tv = new TextView(binding.getRoot().getContext());
tv.setTextSize(16);
tv.setTextAlignment(View.TEXT_ALIGNMENT_CENTER);
tv.setPadding(40,180*(logs.size()+1),40,0);
tv.setText(logs.get(logs.size()-1));
Runnable r = new Runnable() {
#Override
public void run() {
cl.addView(tv);
}
};
h.post(r);
h = null;
r = null;
}
And it solved.

ScrollView doesn't scroll programmatically in a Thread

So what i want to do basically is to scroll the scroll view as the client app sends the command. The method handleScrolling() works in the onCreate() but whenever i call it from the Thread, it doesn't scroll. I think that calling it from the Thread is the problem.
public class TeleprompterActivity extends Activity {
static ScrollView mScrollView;
TextView teleprompterTextView;
String message;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_teleprompter);
teleprompterTextView = findViewById(R.id.teleprompter_text_view);
teleprompterTextView.setText(MainActivity.contents);
mScrollView = findViewById(R.id.scroll);
Thread mThread = new Thread(new ServerClass());
mThread.start();
handleScrolling(3, true);
Log.e("TELE", "handleScrolling at start onCrete");
}
void handleScrolling(final int numLines, final boolean next) {
mScrollView.post(new Runnable() {
public void run() {
int currPosition = mScrollView.getScrollY();
int textSize = (int) teleprompterTextView.getTextSize();
if (next) {
int newPos = currPosition + (textSize * numLines);
mScrollView.smoothScrollTo(0, newPos);
}
if (!next) {
int newPos = currPosition - (textSize * numLines);
if (newPos < 0) {
newPos = 0;
}
mScrollView.scrollTo(0, newPos);
}
}
});
}
void handleMessage(String message) {
if (message.contains("NEXT:")) {
try {
int numLine = Integer.parseInt(message.substring(5));
handleScrolling(numLine, true);
return;
} catch (NumberFormatException nFE) {
nFE.printStackTrace();
Toast.makeText(TeleprompterActivity.this, "Number Format Exception", Toast.LENGTH_SHORT).show();
}
}
if (message.contains("BACK:")) {
try {
int numLine = Integer.parseInt(message.substring(5));
handleScrolling(numLine, false);
} catch (NumberFormatException nFE) {
nFE.printStackTrace();
Toast.makeText(TeleprompterActivity.this, "Number Format Exception", Toast.LENGTH_SHORT).show();
}
}
}
public class ServerClass implements Runnable {
ServerSocket serverSocket;
Socket socket;
DataInputStream dataInputStream;
String receivedData;
Handler handler = new Handler();
#Override
public void run() {
try {
serverSocket = new ServerSocket(8080);
Log.e("TELE", "WAITIN FOR CLIENT");
while (true) {
socket = serverSocket.accept();
dataInputStream = new DataInputStream(socket.getInputStream());
receivedData = dataInputStream.readUTF();
handler.post(new Runnable() {
#Override
public void run() {
message = receivedData;
handleMessage(message);
}
});
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
The handleScrolling() method works perfectly when called outside the Thread. Is it any problem of reference or something like that.
Thanks..

Never update UI components from a thread directly ,call Activity's runOnUiThread so you can use code construct like below:
public class TeleprompterActivity extends Activity {
static ScrollView mScrollView;
TextView teleprompterTextView;
String message;
Activity thisActivity;//<--- used for saving reference to this Activity
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_teleprompter);
teleprompterTextView = findViewById(R.id.teleprompter_text_view);
teleprompterTextView.setText(MainActivity.contents);
mScrollView = findViewById(R.id.scroll);
thisActivity = this;//<---- saving a reference to this activity
Thread mThread = new Thread(new ServerClass());
mThread.start();
handleScrolling(3, true);
Log.e("TELE", "handleScrolling at start onCrete");
}
void handleScrolling(final int numLines, final boolean next) {
thisActivity.runOnUiThread(new Runnable()//<--used thisActivity.runOnUiThread here
{
public void run() {
int currPosition = mScrollView.getScrollY();
int textSize = (int) teleprompterTextView.getTextSize();
if (next) {
int newPos = currPosition + (textSize * numLines);
mScrollView.smoothScrollTo(0, newPos);
}
if (!next) {
int newPos = currPosition - (textSize * numLines);
if (newPos < 0) {
newPos = 0;
}
mScrollView.scrollTo(0, newPos);
}
}
});
}

Handlers don't end after calling removeCallbacksAndMessages(null)

I have two handlers. Handler in a handler. Both of them are in a for-loop.
The overview is something like this,
for{
handler.postDelayed(runnableA{
for{
handler2.postDelayed(runnableB{
function();
}, 3000);
}
}, 1000);
}
I wanted to end handlers' work at any time when the user clicks back button. So, I created two Runnable Classes so that I can use something like runnableA.removellbacksAndMessages(null).
Handler messageHandler;
Handler countDownHandler;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toast.makeText(this, "Start Play in 5 seconds", Toast.LENGTH_SHORT).show();
countDownHandler = new Handler();
for (int i = 7; i >= 0; --i) {
final int idx = i;
Runnable countRunnable = new CountRunnable(idx, countDownView);
countDownHandler.postDelayed(countRunnable, 1000 * (7 - i));
}
}
And this is Runnable Classes.
public class CountRunnable implements Runnable {
int idx;
TextView countDownView;
public CountRunnable(int idx, TextView countDownView) {
this.idx = idx;
this.countDownView = countDownView;
}
#Override
public void run() {
int messageSize = messageItems.size();
for (int j = 0; j < messageSize; j++) {
final int jdx = j;
messageHandler = new Handler();
Runnable messageRunnable = new MessageRunnable(jdx);
messageHandler.postDelayed(messageRunnable, 3000 * jdx);
}
}
}
class MessageRunnable implements Runnable {
int jdx;
public MessageRunnable(int jdx) {
this.jdx = jdx;
}
#Override
public void run() {
addMessageView(messageItems.get(jdx));
}
}
This is onBackPressed():
#Override
public void onBackPressed() {
super.onBackPressed();
Toast.makeText(getApplicationContext(), "All Work Ended.", Toast.LENGTH_SHORT).show();
scrollFlag = true;
try {
messageHandler.removeCallbacksAndMessages(null);
} catch (Exception e) {
Log.d(TAG, "messageHandler never used");
e.printStackTrace();
}
try {
countDownHandler.removeCallbacksAndMessages(null);
} catch (Exception e) {
e.printStackTrace();
}
}
public void addMessageView(String message){
try{
mTextView.setText(message);
}catch(Exception e){
Toast.makeText(getApplicationContext(), "Abnormal End", Toast.LENGTH_SHORT).show();
}
}
But, I keep getting errors because the activity already ended but the handlers can't find the activity. So, Abnormal End Toast message shows as many as the size of inner for loop.
I can ignore this if I don't use the Toast message, but I am afraid of Memory leak or Bad formed Program or something like that.
How can I fix this problem?

The main problem is that you are creating n numbers of CountRunnables and m number MessageRunnables. Despite creating more than one numbers of handlers you are removing callbacks only for the latest-created Hanlder.
Here's what you should do:
Keep a reference of all the Handlers and Runnables and call messageHandler.removeCallbacksAndMessages(null); and countDownHandler.removeCallbacksAndMessages(null); on all of them.

delay inside for loop, make toast every 2 seconds

So hi everyone, this is my first post in stackoverflow,
and i get stucked in 1 problem,
the problem is:
how can I add a delay inside for loop
I did lots of research and none of it works
So I decided to ask myself.
Here is my code
Handler handler1 = new Handler();
for (langId = 1; langId <= 3; langId++) {
handler1.postDelayed(new Runnable() {
#Override
public void run() {
if (langId == 1) {
Toast.makeText(KCRdestActivity.this, "1", Toast.LENGTH_LONG).show();
delayTime += 2000;
}
if (langId == 2) {
Toast.makeText(KCRdestActivity.this, "2", Toast.LENGTH_LONG).show();
delayTime += 2000;
}
if (langId == 3) {
Toast.makeText(KCRdestActivity.this, "3", Toast.LENGTH_LONG).show();
delayTime += 2000;
}
}
}, delayTime);
}
So the result I want is:
"1" -> 2000ms -> "2" -> 2000ms -> "3"
Any ideas?
I tried Thread.sleep(2000), it works, but it freeze the app, I need to do extra things during the process.
Edit
Problem solved, this is the working code, also my final goal
playBtn2.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
final Handler handler1 = new Handler();
langId = 1;
max = 1;
delayTime = 0;
selectedMP = 1;
if (((RadioButton) findViewById(R.id.noneDepart)).isChecked()) max = 3;
else max = 6;
handler1.post(new Runnable() {
#Override
public void run() {
if (((RadioButton) findViewById(R.id.noneDepart)).isChecked()) {
String destdir = "KCR/Depart/" + Utils.getDestID(selectedDest) + "_";
if (viaRAC.isChecked()) destdir = destdir + "via_rac_";
destdir = destdir + langId + ".mp3";
if (selectedMP == 1) {
try {
afd = getAssets().openFd(destdir);
mp1.reset();
mp1.setDataSource(afd.getFileDescriptor(), afd.getStartOffset(), afd.getLength());
mp1.prepare();
mp1.start();
//Utils.RunOnUiThread(KCRdestActivity.this, mp1, sb1);
((Button) findViewById(R.id.Play1)).setText("❙❙");
selectedMP = 2;
delayTime = mp1.getDuration() - 130;
Toast.makeText(KCRdestActivity.this, delayTime + "##" + destdir, Toast.LENGTH_LONG).show();
} catch (Exception e) {
e.printStackTrace();
}
} else {
try {
afd = getAssets().openFd(destdir);
mp2.reset();
mp2.setDataSource(afd.getFileDescriptor(), afd.getStartOffset(), afd.getLength());
mp2.prepare();
mp2.start();
//Utils.RunOnUiThread(KCRdestActivity.this, mp1, sb1);
((Button) findViewById(R.id.Play1)).setText("❙❙");
selectedMP = 1;
delayTime = mp2.getDuration() - 130;
Toast.makeText(KCRdestActivity.this, delayTime + "##" + destdir, Toast.LENGTH_LONG).show();
} catch (Exception e) {
e.printStackTrace();
}
}
}
if (langId > 3) {
return;
}
langId++;
handler1.postDelayed(this, delayTime);
}
});
}
});

Handler handler1 = new Handler();
int langId = 1;
handler1.postDelayed(new Runnable() {
#Override
public void run() {
if (langId > 3) {
return;
}
if (langId == 1) {
Toast.makeText(KCRdestActivity.this, "1", Toast.LENGTH_LONG).show();
delayTime = 2000;
}
if (langId == 2) {
Toast.makeText(KCRdestActivity.this, "2", Toast.LENGTH_LONG).show();
delayTime = 2000;
}
if (langId == 3) {
Toast.makeText(KCRdestActivity.this, "3", Toast.LENGTH_LONG).show();
delayTime = 2000;
}
langId++;
handler1.postDelayed(this, delayTyme);
}
}

There's no need to write that much lines of code, try this:
Handler handler1 = new Handler();
int langId = 1;
handler1.post(new Runnable() {
#Override
public void run() {
if (langId > 3) {
return;
}
Toast.makeText(KCRdestActivity.this, String.valueOf(langId++), Toast.LENGTH_LONG).show();
handler1.postDelayed(this, 2000); // If delay time is constant!
}
});

you can use asyntask along with Thread.sleep(2000) in the doInBackground method

try this..
MainActivity.....
long Delay = 2000;
oncreate().........
Timer Run = new Timer();
TimerTask Show = new TimerTask() {
#Override
public void run() {
do something.........
}
};
Run.schedule(Show, Delay);
}

You need to move your code out of run method and put into for loop directly. Put only toast inside run method.
1. Implement a timer task and schedule it after every 2seconds
int value = 1;
Timer timer = new Timer();
TimerTask task = new TimerTask() {
#Override
public void run() {
Toast.makeText(KCRdestActivity.this, value, Toast.LENGTH_LONG).show();
value++;
}
};
timer.schedule(task, 2000);
OR
2. Change your code to
Try
for (langId = 1; langId <= 3; langId++) {
delayTime += 2000;
Handler handler = new Handler();
handler.postDelayed(new Runnable() {
#Override
public void run() {
Toast.makeText(KCRdestActivity.this, String.valueOf(langId), Toast.LENGTH_LONG).show();
}
}, delayTime);
}

You can use an AsyncTask for this.
public class MyAsyncTask extends AsyncTask<Void, Integer, Void> {
#Override
protected Void doInBackground(Void... params) {
for (int langId = 1; langId <= 3; langId++) {
publishProgress(langId);
try {
Thread.sleep(2000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
return null;
}
#Override
protected void onProgressUpdate(Integer... values) {
super.onProgressUpdate(values);
Toast.makeText(KCRdestActivity.this, String.valueOf(values[0]), Toast.LENGTH_LONG).show();
}
}

use this method
declare global these classes
private int TIME_STAMP_INTERVAL = 2000;
private Runnable runnable = null;
private int count=0;
final Handler handler = new Handler();
then add this in method which u call
runnable = new Runnable() {
#Override
public void run() {
Toast.makeText(context, ""count++, Toast.LENGTH_SHORT).show();
handler.postDelayed(runnable, TIME_STAMP_INTERVAL);
}
};
handler.post(runnable);

A quick and dirty way to achieve this using Thread.sleep(2000):
public static void main(String[] args) {
Runnable forLoop = () -> {
for (int i = 1; i <= 3; i++) {
System.out.print(i); // Do your stuff
try {
Thread.sleep(2000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
};
new Thread(forLoop).start();
}
Output:
1 -> 2000ms -> 2 -> 2000ms -> 3

Stuck in a loop, freezing the android app

I found out that when i pressed a button to run a while loop, the android app will freeze although the program can run. It seem that i stuck in a loop and i want to make a thread to show the GUI and the other for the main code . I'm new in java and i'm self-learned so i would appreciated if anyone could give me an example how to prevent the app from freezing.
I'm sorry if i didn't explain my problem well.
Thank you
Here is my code
public class TachoCount extends Thread {
public boolean isConnected;
protected static final String TAG = "TachoCount";
NXTConnector conn;
//_message = (TextView) findViewById(R.id.messageText);
//final TextView textView = (TextView) findViewById(R.id.textView1);
public static NXTConnector connect(final CONN_TYPE connection_type) {
Log.d(TAG, " about to add LEJOS listener ");
NXTConnector conn = new NXTConnector();
conn.setDebug(true);
conn.addLogListener(new NXTCommLogListener() {
public void logEvent(String arg0) {
Log.e(TAG + " NXJ log:", arg0);
}
public void logEvent(Throwable arg0) {
Log.e(TAG + " NXJ log:", arg0.getMessage(), arg0);
}
});
switch (connection_type) {
case LEGO_LCP:
conn.connectTo("btspp://NXT", NXTComm.LCP);
break;
case LEJOS_PACKET:
conn.connectTo("btspp://");
break;
}
return conn;
}
public TachoCount() {
}
public void closeConnection() {
try {
Log.d(TAG, "TachoCount run loop finished and closing");
conn.getNXTComm().close();
} catch (Exception e) {
} finally {
conn = null;
}
}
public void establishConnection(){
conn = TachoCount.connect(CONN_TYPE.LEGO_LCP);
NXTCommand.getSingleton().setNXTComm(conn.getNXTComm());
NXTInfo info = conn.getNXTInfo();
if (info.connectionState== NXTConnectionState.LCP_CONNECTED)
{
isConnected = true;
// set
//textView.setText("NXT is here");
}
}
public void forward(){
Motor.A.setSpeed(300);
Motor.C.setSpeed(300);
Motor.A.forward();
Motor.C.forward();
}
public void backward(){
Motor.A.setSpeed(300);
Motor.C.setSpeed(300);
Motor.A.backward();
Motor.C.backward();
}
public void byebye(){
Motor.A.stop();
Motor.C.stop();
}
public int getSensorValue()
{
int val = 0;
LightSensor ls = new LightSensor(SensorPort.S3);
val = ls.readValue();
return val;
}
public void linefollower()
{
run();
}
public void run()
{
int min = 30, max = 37, readLight = 0, Mspeed = 90, Mspeed2 = 20;
LightSensor ls = new LightSensor(SensorPort.S3);
while(true){
Motor.A.forward();
Motor.C.forward();
readLight = ls.readValue();
LeJOSDroid.sendMessageToUIThread("Sensor: "+ls.readValue());
if (readLight < min){
readLight = min+1;
}
if (max < readLight){
readLight = max-1;
}
Motor.C.setSpeed(Mspeed + (Mspeed2 * (readLight - min)));
Motor.A.setSpeed(Mspeed + (Mspeed2 * (max - readLight)));
}
}
i tried to change the code. It runs well (although the reading of the
sensor doesn't seem accurate), but then when i push another button,
nothing happens
public void linefollower()
{
Thread thread = new Thread(runnable);
thread.start();
}
Runnable runnable = new Runnable ()
{
public void run(){
int min = 30, max = 37, readLight = 0, Mspeed = 90, Mspeed2 = 20;
LightSensor ls = new LightSensor(SensorPort.S3);
while(true){
Motor.A.forward();
Motor.C.forward();
readLight = ls.readValue();
LeJOSDroid.sendMessageToUIThread("Sensor: "+ls.readValue());
if (readLight < min){
readLight = min+1;
}
if (max < readLight){
readLight = max-1;
}
Motor.C.setSpeed(Mspeed + (Mspeed2 * (readLight - min)));
Motor.A.setSpeed(Mspeed + (Mspeed2 * (max - readLight)));
}
}
};

Try using Runnable or background worker

Your loop looks infinite, it's always true. Also, it's probably better to do heavy tasks in an asynctask activity.
Check the official info: http://developer.android.com/reference/android/os/AsyncTask.html