I modified the standard Bluetoothchat example to send 4 bytes of data at a time to a bluetooth device every half a second. It works fine if I start the App fresh. However, there is a problem if I reconnect as follows:
While Bluetooth is connected, I click the connect button again on the menu and select the same device. This disconnects the bluetooth (not sure whether this is the right procedure to disconnect). Then, I connect again by selecting the device, and it will be reconnected. After reconnection, a very strange problem appears: instead of sending the data every half a second, it will send the data every quarter a second. If I go through the process again and reconnect, the time interval will become even shorter. It gets to a point that the bluetooth device on the receiving end can't keep up with the data. At this point, the only way out is to kill the app and restart again. Then everything becomes normal, till next time I try to reconnect again.
I have tried different things but nothing appear to fix this. For example, I made sure the thread sending the data is killed when disconnected so no multiple threads are sending the data. I was wondering whether the baud rate changed when reconnected, but then why would the baud rate affect the Thread.sleep(500); statement (which is responsible for controlling the half a second data send). Any help would be greatly appreciated.
Here is the code, the SendClass is created under the MainActivity:
class SendClass implements Runnable {
public void run() {
bytearr[0]=0;bytearr[1]=0;bytearr[2]=0;bytearr[3]=0;
while (!Thread.currentThread().isInterrupted()) {
if (mChatService==null || mChatService.getState()
!=BluetoothChatService.STATE_CONNECTED) {
continue;
} else {
try {
Thread.sleep(500);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
mChatService.write(bytearr);
}
}//end of run
}//end of runnable
Then under STATE_CONNECTED:
case BluetoothChatService.STATE_CONNECTED:
setStatus(getString(R.string.title_connected_to,mConnectedDeviceName));
/*
if(sendingThread!=null){
//sendingThread.stop();
sendingThread.interrupt();
if(D) Log.i(TAG, "after sendingThread");
sendingThread = null;
}*/
sendingThread = new Thread(new SendClass());
sendingThread.start();
break;
As you can see, I tried to kill the thread before creating a new one but that didn't make any difference. Any suggestions?
You are creating a thread that never actually stops, even after you create a new thread and assign to the same variable that particular thread wont stop running.
You need to make sure that the thread will stop after it disconnects.
Here is my suggestion
Change your SendClass to:
class SendClass implements Runnable {
private boolean stopped = false;
public void setStopped(boolean s){
this.stopped = s;
}
public void run() {
bytearr[0]=0;bytearr[1]=0;bytearr[2]=0;bytearr[3]=0;
while (!Thread.currentThread().isInterrupted() && !stopped) {
if (mChatService==null || mChatService.getState() !=BluetoothChatService.STATE_CONNECTED) {
continue;
} else {
try {
Thread.sleep(500);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
mChatService.write(bytearr);
}
}//end of run
}//end of runnable
Then when you start your thread keep the reference to the Runnable so you can call the setStopped(true); like this
SendClass sc = new SendClass();
sendingThread = new Thread(sc);
sendingThread.start();
When you disconnect the bluetooth dont forget to call sc.setStopped(true); so your thread will finish by not going into the while.
Related
I want to send five data to Bluetooth. First one is turn on and second one is turn off, third one is turn on, and so on... I want post delay between turn on and turn off (about 1 second). Which is best one to do it. Currently, I am using sleep in Thread class
for (int i=1;i<5;i++) {
try {
if(i%2==0){
send(1);
Thread.sleep(500);
}
else{
send(0);
Thread.sleep(500);
}
} catch (InterruptedException e) {
e.printStackTrace();
}
}
I have a Runnable r that is triggered periodically once per minute by handler.postDelayed(60*1000). And I test my code on a real device.
However I notice, when the phone is charging (AC or USB) , it works well, but if the phone is disconnected, the Runnable r will only run once every 20min or even worse, several hours. Thanks for any help!
Below is the code:
private final Runnable listen_to_server = new Runnable(){
public void run(){
new Thread() {
public void run() {
try {
handler.sendMessage(handler.obtainMessage(PING_SERVER,"listen"));
synchronized (listen) {
listen.wait();
}
handler.postDelayed(listen_to_server, 50000);
}
catch (Exception e) {
e.printStackTrace();
}
}
}.start();
}
};
In the Handler:
handler=new Handler() {
#Override
public void handleMessage(final Message msg) {
switch (msg.what) {
case PING_SERVER:
String type = (String) msg.obj;
add_log("ping server"); // print to screen and Log.d
...
...
}
}
}
Referring to this link i think the problem might be, as they said:
Android is not a real-time operating system. All postDelayed()
guarantees is that it will be at least the number of milliseconds
specified. Beyond that will be dependent primarily on what the main
application thread is doing (if you are tying it up, it cannot process
the Runnable), and secondarily on what else is going on the device
(services run with background priority and therefore get less CPU time
than does the foreground).
How to fix this? in this post the solution was the following:
You'll probably have better luck using the AlarmManager for such a
long delay. Handler is best for ticks and timeouts while your app is
in the foreground.
so try implement an AlarmManager looking at the doc.
Hope i helped :)
I keep getting an illegal argument exception when running my app. However, this happens prior to the Toast messages coming up and that's why I think I need a delay.
Prior to adding on the DatabaseHelper class, my app was running and the proper value was coming up on both Toast messages, the one in the MainActivity and the one showing the intent value passed in the DisplayResult activity.
I'm not sure what to do at this point.
Just do a thread sleep in a runnable.
int timeYouWantToSleep = 60000;
new Thread(new Runnable() {
public void run() {
try {
Thread.sleep(timeYouWantToSleep);
//do your work here
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}).start();
If this doesn't work, you know it's not a delay that you need.
im making an app that should send a message after certain amount of time via bluetooth.
The thread works fine when i use "Log" but when i use the write function of bluetooth, it seems to executes the loop when the app wants.
Hope somebody can help me:
public class AsyncWrite extends Thread {
#Override
public void run() {
while(true) {
try {this.sleep(250);} catch (Exception E) {}
//Log.e(TAG,"Test run");
mConnectedThread.write(A);
}
}
}
I've already try using asynctask executors and handlers, the result it's the same.
I'm working on a memory game for Android and I'm having a problem. When the user taps the second image - if the images are not the same I want the second image to show for 1, 2 seconds.
What I've tried is to sleep for 1-2 sec. the UI thread after the second image is activated - but this doesn't seem to work - the second image doesn't seem to show! (only the first images is showed)
Here's my code:
public void whenTapedImage(View v, int position)
{
i++;
ImageView imgV=(ImageView)v;
if(i%2!=0)
{
firstClick=position;
imgV.setImageResource(im.images.get(firstClick));
}
else
{
secondClick=position;
imgV.setImageResource(im.images.get(secondClick));
try {
Thread.currentThread().sleep(1000);
if(!(im.images.get(firstClick).equals(im.images.get(secondClick))))
{
Toast.makeText(easyGame.this, "Try Again!", Toast.LENGTH_SHORT).show();
im.notifyDataSetChanged();
gridview.setAdapter(im);
gridview.invalidate();
aux=player1Turn;
player1Turn=player2Turn;
player2Turn=aux;
}
else{
done=done+2;
ImageAdapter.keepVisibleViews.add(firstClick);
ImageAdapter.keepVisibleViews.add(secondClick);
if(player1Turn==true)
{
player1Score++;
String score=Integer.toString(player1Score);
score1.setText(score);
}
if(player2Turn==true)
{
player2Score++;
String score=Integer.toString(player2Score);
score2.setText(score);
}
}
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
What am I doing wrong?
You must not sleep the UI thread as this would prevent android from delivering any other events to your activity's UI.
Instead, do something such as use a timer and have the timer's method use the run on ui thread facility to make the desired postponed change.
For robustness you may need to implement a state machine (either formally, or in effect) to keep track of what is supposed to be happening - you'll need to decide if the current delay should be aborted or enforced if another button is pushed, and make the state machine treat that appropriately.
This is similar to Waiting in android app
Try following the solution posted there and use the Timer Class