Develop Reference

Thread runs After activity life cycle?

I have network operation inside a thread which in oncreate() based on network response I need to process the next step but the thread is running after the activity life cycle.
I called networkRequest() in oncreate() in activity
private void networkRequest() {
final String[] resp = new String[1];
Thread thread = new Thread(new Runnable() {
#Override
public void run() {
try {
resp[0] = AttemptingUploadCheckList.getJsonObj(url);
JSONObject response = new JSONObject(resp[0]);
if (response != null) {
version_code = response.getInt("version_code");
recommended_update = response.getBoolean("recommended_update");
forced_update = response.getBoolean("forced_update");
}
if (recommended_update) {
recomendUpadate();
} else if (forced_update)
onUpdateNeeded(url);
else {
Intent intent = new Intent(SplashActivity.this, LoginActivity.class);
startActivity(intent);
finish();
}
} catch (Exception e) {
e.printStackTrace();
}
}
});
thread.start();
}

Thread is not bound with the activity. It's not running with the main thread.
Android said if you want to perform any long running tasks like api call, data from database then you need to use the AsyncTask or the Service.
In your case, you can use the AsycnTask for the fetching data.
class MyAsync extends AsyncTask<Void, Void, Void>{
final String[] resp = new String[1];
JSONObject response;
#Override
protected void onPreExecute() {
super.onPreExecute();
// Show Progress Dialog
}
#Override
protected void onPostExecute(Void aVoid) {
super.onPostExecute(aVoid);
// Hide Progress Dialog
if (response != null) {
version_code = response.getInt("version_code");
recommended_update = response.getBoolean("recommended_update");
forced_update = response.getBoolean("forced_update");
}
if (recommended_update) {
recomendUpadate();
} else if (forced_update)
onUpdateNeeded(url);
else {
Intent intent = new Intent(SplashActivity.this, LoginActivity.class);
startActivity(intent);
finish();
}
}
#Override
protected Void doInBackground(Void... voids) {
try {
resp[0] = AttemptingUploadCheckList.getJsonObj(url);
response = new JSONObject(resp[0]);
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
}
For executing the above AsynTask
private void networkRequest() {
new MyAsync().execute();
}

Thread does not care about Activity or any other Component's lifecycle Except the Process in which it is Running.
You need to check for state of component yourself.
I can provide some example code but i really do not understand what exactly you are trying to do .
Considering you are making a network request there. Java thread individually is hard to handle in such cases considering the fact that after response we need to move on to Main thread to update the UI. So i highly recommend you should use a Network API Library probably RetroFit .
You can check state of the Component like isFinishing() in Activity .

Android Timed Async Task

Hi currently i have the following code which utilizes Asycn Task and Timer.
My async task is basically trying to send a HTTP GET method from a URL where the response from the server could varies depending on connection and load.
What i would like to do is to have a timed async task. Where, it will schedule an AsyncTask every X second BUT if there is currently an Async Task in progress i would have to kill it first. Then start a new one.
Here is the code that i have at the moment:
private static boolean running = false;
Timer myTimer;
protected void onCreate(Bundle savedInstanceState) {
/* REST OF CODE OMITTED */
MyTimerTask myTask = new MyTimerTask();
myTimer = new Timer();
myTimer.schedule(myTask, 0, 10000);
}
/* REST OF CODE OMITTED */
private class MyTimerTask extends TimerTask {
public void run() {
if(!running){
Log.i("TAG", "NEW TIMER STARTED.");
RetrieveChatMessage task = new RetrieveChatMessage();
task.execute();
running = true;
}else{
running = false;
}
}
}
private class RetrieveChatMessage extends AsyncTask<String, Void, ArrayList<Chat>> {
#Override
protected ArrayList<Chat> doInBackground(String... params) {
// TODO Auto-generated method stub
ArrayList<Chat> cList = null;
String jResult = null;
Log.i("TAG", "RETRIEVING CHAT MESSAGE");
try {
jResult = ((new HttpRetriever())).getChatList(mAccount.email, mAccount.passwd);
} catch (UnsupportedEncodingException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (NoSuchAlgorithmException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
try {
if(jResult != null){
Log.i("TAG", "JSON DATA: " + jResult);
cList = (new ChatHandlers()).getChatList(jResult);
}else{
cList = null;
}
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
Log.e("TAG", "JSON Exception " + e.toString());
}
return cList;
}
#Override
protected void onPostExecute(final ArrayList<Chat> result) {
Log.i("TAG", "ON POST EXECUTE");
if(result != null){
// Do something here
}
}
}
To be honest the code above works with slight issues:
1. It seems to execute the Async randomly, instead of every 10 seconds.
2. When i go to another activity, somewhat it prevents other Async task from doing its job (Which is also trying to retrieve JSON response from server).
I am not too worried about the later problem (and that is not the question i am asking). I just would like to know how to have a proper timed Async Task. Can anyone point me to a direction.
Thank you.
EDIT #1:
after reading #thepoosh comment's i tried the following (i put it in onCreate):
scheduleTaskExecutor= Executors.newScheduledThreadPool(5);
scheduleTaskExecutor.scheduleAtFixedRate(new Runnable() {
public void run() {
// Parsing RSS feed:
// myFeedParser.doSomething();
Log.w("THUMBQOO", "NEW TASK STARTED");
retrieveChat();
}
}, 0, 15, TimeUnit.SECONDS);
Result: i have a consistent execution of Task. However, it seems that retrieveChat(); is never be called after the first execution.

Actually AsyncTask is not used for long operations .Check Here
You should use a Thread that uses a interface to notify UI or you can simply use a Handler which is the most Preffered way in android. Simply you can do a task repeatedly for every 10 seconds by
handler.postDelayed(new Runnable() {
#Override
public void run() {
// do work
handler.postDelayed(10000);
}
}, 10000);

Declare a Handler object to maintain future task executor...
private Handler mTimerHandler = new Handler();
Write a thread which will execute your future task...
private Runnable mTimerExecutor = new Runnable() {
#Override
public void run() {
//write your code what you want to do after the specified time elapsed
if(!running){
RetrieveChatMessage task = new RetrieveChatMessage();
task.execute();
running = true;
}else{
running = false;
}
}
};
Call your future tast executor with time using hanlder...
mTimerHandler.postDelayed(mTimerExecutor, 10000);
You can cancle your future task executor any time by this...
mTimerHandler.removeCallbacks(mTimerExecutor);

I am not sure if this is a very good way of accomplishing this (my answer here below) :
Use a Handler, create a HandlerThread and keep posting messages to this handler.
For the handlers "handleMessage" method, you can do your task and again send a message back to the MessageQueue.
HandlerThread thread = new HandlerThread(<name>);
thread.start();
Looper looper = thread.getLooper();
CustomHandler handler = new CustomHandler(looper);
// The CustomHandler class
class CustomHandler extends Handler {
public CustomHandler(Looper looper) {
super(looper);
}
#Override
public void handleMessage(Message msg) {
//Do your operation here
handler.sendEmptyMessageDelayed(msg, <delayTime>);
}
}

Android does thread end itself after executing code

So, I'm searching on net for a while and now I'm confused... do I need to explicitly end thread after code is executed or thread does it automatically?
Code:
Runnable waitForInput = new Runnable() {
public void run() {
while (!inputOK) {
try {
Thread.sleep(100);
} catch (Exception e) {}
}
if (!ret_val.equals("")) {
port = ret_val;
}
inputOK = false;
ret_val = "";
}
};
Thread inputW = new Thread(waitForInput);
inputW.start();

The Thread ends when the method run ends. Since you have while loop you have to force explicitly the exit condition

how to link process output to textview and automatically update in realtime?

I'm not the best programmer, actually, I'm pretty bad :(
I need help with something thats driving my crazy. basically I have a tcpdump process, I want to extract the output and put it into a textview which is updated every few milliseconds, I've tried everything and just cant get it to work.
I don't get any errors and it seems to work in the background, but only displays chunks of text only after I go to the homescreen and return back into the app. however, it doesnt constantly update the textview, and sometimes hangs and crashes.
I've created a simple handler which can update the textview with plain text without problems, but then i faced major problems getting it to read the process.
Begin button
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.capture);
this.LiveTraffic = (TextView) findViewById(R.id.LiveTraffic);
this.CaptureText = (TextView) findViewById(R.id.CaptureText);
((TextView) findViewById(R.id.ipv4)).setText(getLocalIpv4Address());
((TextView) findViewById(R.id.ipv6)).setText(getLocalIpv6Address());
//Begin button
final Button startButton = (Button) findViewById(R.id.start);
startButton.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
Toast.makeText(getApplicationContext(), "Now Capturing Packets", Toast.LENGTH_LONG).show();
try {
process = Runtime.getRuntime().exec("su");
DataOutputStream os = new DataOutputStream(process.getOutputStream());
os.writeBytes("/data/local/tcpdump -q\n");
os.flush();
os.writeBytes("exit\n");
os.flush();
os.close();
inputStream = new DataInputStream(process.getInputStream());
Thread.sleep(1000);
Process process2 = Runtime.getRuntime().exec("ps tcpdump");
DataInputStream in = new DataInputStream(process2.getInputStream());
String temp = in.readLine();
temp = in.readLine();
temp = temp.replaceAll("^root *([0-9]*).*", "$1");
pid = Integer.parseInt(temp);
Log.e("MyTemp", "" + pid);
process2.destroy();
CaptureActivity.this.thisActivity.CaptureText.setText("Active");
} catch (Exception e) {
}
ListenThread thread = new ListenThread(new BufferedReader(new InputStreamReader(inputStream)));
thread.start();
}
});
}
ListenThread class
public class ListenThread extends Thread {
public ListenThread(BufferedReader reader) {
this.reader = reader;
}
private BufferedReader reader = null;
#Override
public void run() {
reader = new BufferedReader(new InputStreamReader(inputStream));
while (true) {
try {
CaptureActivity.this.thisActivity.CaptureText.setText("exec");
int a = 1;
String received = reader.readLine();
while (a == 1) {
CaptureActivity.this.thisActivity.LiveTraffic.append(received);
CaptureActivity.this.thisActivity.LiveTraffic.append("\n");
received = reader.readLine();
CaptureActivity.this.thisActivity.CaptureText.setText("in loop");
}
CaptureActivity.this.thisActivity.CaptureText.setText("out loop");
} catch (Exception e) {
Log.e("FSE", "", e);
}
}
}
}

I am not an android expert but I notice that:
you are running I/O operations in the UI thread - that will freeze your GUI until the I/O operation finishes ==> run them in a separate thread.
you update the UI from outside the UI thread in ListenThread, which can lead to unexpected results
You can read more about it in this tutorial (make sure you read the 2 examples as the first one is broken (on purpose)).
EDIT
In conclusion you should have something like this in your first piece of code:
startButton.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
Toast.makeText(getApplicationContext(), "Now Capturing Packets", Toast.LENGTH_LONG).show();
new Thread(new Runnable() {
public void run() {
try {
process = Runtime.getRuntime().exec("su");
...
CaptureActivity.this.runOnUiThread(new Runnable() {
public void run() {
CaptureActivity.this.thisActivity.CaptureText.setText("Active");
}
});
} catch (Exception e) {
}
ListenThread thread = new ListenThread(new BufferedReader(new InputStreamReader(inputStream)));
thread.start();
}
}).start();
}
});
and in the second:
while (true) {
try {
CaptureActivity.this.runOnUiThread(new Runnable() {
public void run() {
CaptureActivity.this.thisActivity.CaptureText.setText("exec");
}
});
int a = 1;
String received = reader.readLine();
while (a == 1) {
CaptureActivity.this.runOnUiThread(new Runnable() {
public void run() {
CaptureActivity.this.thisActivity.LiveTraffic.append(received);
CaptureActivity.this.thisActivity.LiveTraffic.append("\n");
CaptureActivity.this.thisActivity.CaptureText.setText("in loop");
}
});
received = reader.readLine();
}
CaptureActivity.this.runOnUiThread(new Runnable() {
public void run() {
CaptureActivity.this.thisActivity.CaptureText.setText("out loop");
}
});
} catch (Exception e) {
Log.e("FSE", "", e);
}
}
That should solve the specific UI interaction issue. But there are other logic problems in your code which go beyond this question (for example the fact that you never test if you have reached the end of the file you are reading, the fact that while(a==1) is an infinite loop because you never change the value of a etc.).

how can I chnage a TextViews text from a thread?

I'm trying to write code to pull a server every second for updated messages. The messages then get displayed in a text view. If I do not change the text in the text view it runs fine. It will crash if I try to change the textview on the thread. IF i change it not on the thread works fine.
I'm assuming the thread cannot access the main threads memory? How can I set the text in the view with the text just loaded over the internet?
In the code below I have a thread that does a endless loop with a sleep. It calls a method called SendMessage. Send Message loads in text over the internet and at the end tries to update the View with it. It causes a exception when this happens.
code:
public class cChat extends cBase implements OnClickListener {
/** Called when the activity is first created. */
TextView mUsers;
TextView mComments;
int i=0;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.chat);
mUsers=( TextView) findViewById(R.id.viewusers);;
mComments=( TextView) findViewById(R.id.viewchats);;
Thread thread = new Thread()
{
#Override
public void run() {
try {
int t=0;
while(true)
{
SendMessage();
sleep(1000*5);
t++;
}
} catch (InterruptedException e) {
e.printStackTrace();
}
}
};
thread.start();
}
public void onClick(View v) {
} // end function
// send a uypdate message to chat server
// return reply in string
void SendMessage()
{
try {
URL url = new URL("http://50.63.66.138:1044/update");
System.out.println("make connection");
URLConnection conn = url.openConnection();
// set timeouts to 5 seconds
conn.setConnectTimeout(1000*5);
conn.setReadTimeout(5*1000);
conn.setDoOutput(true);
BufferedReader rd = new BufferedReader(new InputStreamReader(conn.getInputStream()));
// String line;
String strUsers=new String("");
String strComments=new String("");
String line=new String();
int state=0;
while ((line= rd.readLine() ) != null) {
switch(state){
case 0:
if ( line.contains("START USER"))
state=1;
if ( line.contains("START COMMENTS"))
state=2;
break;
case 1:
if ( line.contains("END USER"))
state=0;
else
{
strUsers+=line;
strUsers+="\n";
}
break;
case 2:
if ( line.contains("END COMMENTS"))
state=0;
else {
strComments+=line;
strComments+="\n";
}
break;
} // end switch
} // end loop
// the next line will cause a exception
mUsers.setText(strUsers);
mComments.setText(strComments);
} catch (Exception e) {
i++; // use this to see if it goes here in debugger
// System.out.println("exception");
// System.out.println(e.getMessage());
}
} // end methed
}

use runOnUiThread as
YOUR_CURRENT_ACTIVITY.this.runOnUiThread(new Runnable() {
#Override
public void run() {
// the next line will cause a exception
mUsers.setText(strUsers);
mComments.setText(strComments);
//....YOUR UI ELEMENTS
}
});
EDIT :
see doc runOnUiThread

You can use a handler to post tasks (Runnables) to the UI/Main Thread:
private Handler handler = new Handler();
//...
Thread thread = new Thread()
{
#Override
public void run() {
try {
int t=0;
while(true)
{
handler.post(new Runnable() {
#Override
public void run() {
SendMessage();
}
});
sleep(1000*5);
t++;
}
} catch (InterruptedException e) {
e.printStackTrace();
}
}
};

You can't touch an UI widget from a thread different than the one used to create it (the UI thread). But if you have a reference to the Activity, you can simply do:
activity.runOnUiThread(new Runnable() {
#Override
public void run() {
mUsers.setText(strUsers);
mComments.setText(strComments);
}
});
which would require strUsers to be accessible by the anonymous class. For that you can simply do:
final String finalUseres = strUsers;
and use finalUsers within run().

Try using a Service to continuously pull/send data to server. This will reduce the load on your UI-Thread.

the Andoid UI toolkit is not thread-safe. So, you
must not manipulate your UI from a worker thread
To fix this problem, Android offers several ways to access the UI thread from other threads. Here is a list of methods that can help:
Activity.runOnUiThread(Runnable)
View.post(Runnable)
View.postDelayed(Runnable, long)
you can also use AsyncTask.
see this tutorial on process and threads in android.