Develop Reference

How to load new values of JSON after every 10 seconds

Hi people I am getting problem in getting my latest JSON value after every 10 seconds. I have developed this code and now I am stucked in this. When I run this code it shows the value after second and did not get updated the second time. I have implemented the handler but it is also not working here.
public class MainActivity extends AppCompatActivity {
TextView a,b,c,d,e,f,g,h;
String result = "";
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
a=(TextView) findViewById(R.id.a);
b=(TextView) findViewById(R.id.b);
c=(TextView) findViewById(R.id.c);
DownloadTask task = new DownloadTask();
task.execute("https://api.thingspeak.com/channels/12345/feeds.json?results=1");
}
public class DownloadTask extends AsyncTask<String, Void, String> {
#Override
protected String doInBackground(String... urls) {
URL url;
HttpURLConnection urlConnection = null;
try {
url = new URL(urls[0]);
urlConnection = (HttpURLConnection) url.openConnection();
InputStream in = urlConnection.getInputStream();
InputStreamReader reader = new InputStreamReader(in);
int data = reader.read();
while (data != -1) {
char current = (char) data;
result += current;
data = reader.read();
}
return result;
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
#Override
protected void onPostExecute(final String result) {
super.onPostExecute(result);
new Handler().postDelayed(new Runnable() {
public void run() {
search(result);
}
}, 10000);
}
public void search(String result){
try {
JSONObject jsonObject = new JSONObject(result);
JSONArray weatherInfo = jsonObject.getJSONArray("feeds");
JSONObject legsobject = weatherInfo.getJSONObject(0);
a.setText(legsobject.getString("field1"));
b.setText(legsobject.getString("field2"));
c.setText(legsobject.getString("field3"));
}catch (JSONException e) {
e.printStackTrace();
}
}
}
}
I want to get my value refreshed after every 10 seconds and it is not doing it.
Can any one guide me that how can I make it possible.

Try this code ..
private final int INTERVAL_MILLI = 60000; // define your time..
Handler mHandler;
#Override
protected void onDestroy() {
super.onDestroy();
mHandler.removeCallbacks(SyncData);
}
Runnable SyncData = new Runnable() {
#Override
public void run() {
// call your code here..
Log.e(TAG, "SyncData1: " + new java.sql.Date(System.currentTimeMillis()).toString());
final String Token = AppSetting.getStringSharedPref(mContext, Constants.USER_KEY_TOKEN, "");
if (!TextUtils.isEmpty(Token) && !CommonUtils.isServiceRunning(mContext)) {
Log.e(TAG, "SyncData2: " + new java.sql.Date(System.currentTimeMillis()).toString());
startService(new Intent(mContext, SyncService.class));
}
callSyncData();
}
};
public void callSyncData()
{
mHandler.postDelayed(SyncData, INTERVAL_MILLI);
}
and callSyncData() method called in activity onCreate method and run method.

To begin with, I don't like the idea of hammering the server with a request every 10s even nothing changes really. If you can move to a solution with notification from the server it will be better.
If you still need to do that you can use three common solutions to fire a repeating task with a period:
1- Use Timer & TimerTask
For this solution you need to declare your timer task to run:
final TimerTask repeatedTask = new TimerTask() {
#Override
public void run() {
//you stuff here
}
};
Then you need to schedule your task using a timer like below:
final Timer timer = new Timer();
timer.scheduleAtFixedRate(repeatedTask,0, 10 * 1000);
==> Don't forget to call timer.cancel(); when your are done (or activity pause, stop, ...)
2- Use ScheduledThreadPoolExecutor
This is basically a replacing for Timer task starting android 5.0. The setup is more easy and straightforward like below:
ScheduledExecutorService executor = Executors.newScheduledThreadPool(1);
executor.scheduleAtFixedRate(new Runnable() {
#Override
public void run() {
//you stuff here
}
}, 0, 10, TimeUnit.SECONDS);
==> don't forget to shutdown your executor when you are done by calling : executor.shutdown();
3- Use Handler
The tip here is to repost the runnable after downloading your json like mentionned in the previous answer.

You can use TimerTask and Timer. If you need to update UI components you should run it on UI thread.
final TimerTask yourRepeatedTask = new TimerTask() {
#Override
public void run() {
runOnUiThread(new Runnable() {
#Override
public void run() {
//your code here
}
});
}
};
And the Timer which schedules your task in a given interval. In your case, it is 10s. Make sure to give the interval in milliseconds.
final Timer timer = new Timer();
timer.scheduleAtFixedRate(yourRepeatedTask ,0, 10 * 1000);
At last call timer.cancel() to stop the timer.
#Override
protected void onPause() {
if (timer != null) {
timer.cancel();
}
super.onPause();
}

Android - Moveing an Activity inside of background thread

Every time I`m trying to finish an activity inside of a timer method, the activity comes back alive over and over again.
I running this activity:
public class PlayerNoAdmin extends ActionBarActivity {
Timer myTimer; boolean isAdmin;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_player_no_admin);
Intent oldIntent = getIntent();
if (oldIntent != null && oldIntent.hasExtra("THE_LIST")){
songs = oldIntent.getParcelableArrayListExtra("THE_LIST");
id = oldIntent.getIntExtra("ID",0);
listId = oldIntent.getIntExtra("LIST_ID",0);
isAdmin = oldIntent.getBooleanExtra("IS_ADMIN",false);
}
//update the list every k seconds
myTimer = new Timer();
myTimer.schedule(new TimerTask() {
#Override
public void run() {
TimerMethod();
}
}, 0, k_time2Update);
}
private void TimerMethod() {
//This method is called directly by the timer
//and runs in the same thread as the timer.
//We call the method that will work with the UI
//through the runOnUiThread method.
this.runOnUiThread(Timer_Tick);
}
private Runnable Timer_Tick = new Runnable() {
public void run() {
//Here check for update in the list every 30 seconds and send the new location
String url = getRunUrl();
new TaskMusicPlay().execute(url);
}
};
private class TaskMusicPlay extends AsyncTask<String, Void, String> {
#Override
protected String doInBackground(String... params) {
String jsonResult = null;
try {
String url = params[0];
TestMain client = new TestMain();
jsonResult = client.doGetRequest(url);
} catch (IOException e) {
e.printStackTrace();
}
return jsonResult;
}
#Override
protected void onPostExecute(String aVoid) {
super.onPostExecute(aVoid);
checkIfNew(aVoid);
}
private void checkIfNew(String result) {
try {
JSONObject object = new JSONObject(result);
String temp = object.getJSONObject("info").getString("isAdmin");
isAdmin = (temp.equals("true"));
if (isAdmin) {
Intent intent = new Intent(getApplication(),YouTubePlayer.class);
intent.putExtra("THE_LIST", songs);
intent.putExtra("ID", id);
intent.putExtra("LIST_ID",listId);
intent.putExtra("IS_ADMIN",isAdmin);
startActivity(intent);
finish();
}
}
} catch (JSONException e) {
e.printStackTrace();
}
}
}
}
At the end, I succeeded to move to the YouTubePlayer activity, but every few seconds the app returns to the code of this activity (and then executes again the startActivity call and goes back to YouTubePlayer) and that's going on and on.

Your Timer is periodically calling the player to start over and over again.
You must make a cancel() call to the Timer if it is no longer needed so you prevent it from holding a reference for your activity and thus preventing from being removed from the backstack and GC.
http://developer.android.com/reference/java/util/Timer.html
And your Timer is not running on the same thread as it's code because the timer thread iis another Thread and the Code in the Timer is running on UI. You can check it out by adding some logs in the Timer's run method outside of the runOnUIThread() and inside of it.

android app shows blank screen (not updating ui) while in a loop

In my application, a client is connected to server. It waits until the connection to the server occurs. During that time the application is not responding. How can i solve this problem. Tried code snippet shows below
public Connection(){
client.SetParent(this);
this.context = g.getContext();
bConnected = false;
mNetworkRunner = new Runnable() {
public void run() {
try {
Log.e("", "mNetworkRunner...");
if( SendKeepAlive()){
Main.conStatus(1);
Log.e("", "SendKeepAlive...");
}
else {
Main.conStatus(0);
Log.e("", "No connection...");
g.log("Connection to server is lost... Trying to Connect...");
while(true){
Log.e("", "In while loop...");
if(!Connect()){
g.log("Trying...");
Log.e("", "In Connect no connect...");
Thread.sleep(2000);
}
else {
g.log("Connected");
break;
}
}
Main.conStatus(1);
}
mNetworkHandler.postDelayed(this, 30000);
}
catch (Exception e) {
e.printStackTrace();
}
}
};
}
//
private void CheckNetworkConnection(){
if( mNetworkHandler == null ){
mNetworkHandler = new Handler();
mNetworkHandler.post(mNetworkRunner);
Log.e("", "CheckNetworkConnection...");
}
}

You are doing a lot of time consuming work in UI Thread, which create problem. In this situation you should use AsyncTask.
AsyncTask enables proper and easy use of the UI thread. This class allows to perform background operations and publish results on the UI thread without having to manipulate threads and/or handlers.
private class DownloadFilesTask extends AsyncTask<URL, Integer, Long> {
protected Long doInBackground(URL... urls) {
//do your time consuming task here
}
protected void onProgressUpdate(Integer... progress) {
//setProgressPercent(progress[0]);
}
protected void onPostExecute(Long result) {
//showDialog("Downloaded " + result + " bytes");
}
}
Once created, a task is executed very simply:
new DownloadFilesTask().execute(url1, url2, url3);

mNetworkHandler = new Handler() will make Runnable execute on UI Thread, you need HandlerThread
private void CheckNetworkConnection(){
if( mNetworkHandler == null ){
HandlerThread handlerThread = new HandlerThread("thread");
handlerThread.start();
mNetworkHandler = new Handler(handlerThread.getLooper());
mNetworkHandler.post(mNetworkRunner);
Log.e("", "CheckNetworkConnection...");
}
}

Update UI from running thread

I want to write a download manager app, in the activity I add a progress bar which show the current progress to the user, now if user touch the back button and re-open the activity again this ProgressBar won't be updated.
To avoid from this problem I create a single thread with unique name for each download that keep progress runnable and check if that thread is running in onResume function, if it is then clone it to the current thread and re-run the new thread again but it won't update my UI either, Any ideas !?
#Override
public void onResume()
{
super.onResume();
Set<Thread> threadSet = Thread.getAllStackTraces().keySet();
Thread[] threadArray = threadSet.toArray(new Thread[threadSet.size()]);
for (int i = 0; i < threadArray.length; i++)
if (threadArray[i].getName().equals(APPLICATION_ID))
{
mBackground = new Thread(threadArray[i]);
mBackground.start();
downloadProgressBar.setVisibility(View.VISIBLE);
Toast.makeText(showcaseActivity.this
, "Find that thread - okay", Toast.LENGTH_LONG).show();
}
}
private void updateProgressBar()
{
Runnable runnable = new updateProgress();
mBackground = new Thread(runnable);
mBackground.setName(APPLICATION_ID);
mBackground.start();
}
private class updateProgress implements Runnable
{
public void run()
{
while (Thread.currentThread() == mBackground)
try
{
Thread.sleep(1000);
Message setMessage = new Message();
setMessage.what = mDownloadReceiver.getProgressPercentage();
mHandler.sendMessage(setMessage);
}
catch (InterruptedException e)
{
Thread.currentThread().interrupt();
}
catch (Exception e)
{/* Do Nothing */}
}
}
private Handler mHandler = new Handler()
{
#Override
public void handleMessage(Message getMessage)
{
downloadProgressBar.setIndeterminate(false);
downloadProgressBar.setProgress(getMessage.what);
if (getMessage.what == 100)
downloadProgressBar.setVisibility(View.GONE);
}
};
Download button code:
downloadBtn.setOnClickListener(new View.OnClickListener()
{
#Override
public void onClick(View arg0)
{
downloadProgressBar.setVisibility(View.VISIBLE);
downloadProgressBar.setIndeterminate(true);
downloadProgressBar.setMax(100);
Intent intent = new Intent(showcaseActivity.this, downloadManagers.class);
intent.putExtra("url", "http://test.com/t.zip");
intent.putExtra("receiver", mDownloadReceiver);
startService(intent);
updateProgressBar();
}
});

I'd strongly recommend reading the Android Developer blog post on Painless Threading. As it states, the easiest way to update your UI from another thread is using Activity.runOnUiThread.

Android: Memory leak due to AsyncTask

I'm stuck with a memory leak that I cannot fix. I identified where it occurs, using the MemoryAnalizer but I vainly struggle to get rid of it. Here is the code:
public class MyActivity extends Activity implements SurfaceHolder.Callback {
...
Camera.PictureCallback mPictureCallbackJpeg = new Camera.PictureCallback() {
public void onPictureTaken(byte[] data, Camera c) {
try {
// log the action
Log.e(getClass().getSimpleName(), "PICTURE CALLBACK JPEG: data.length = " + data);
// Show the ProgressDialog on this thread
pd = ProgressDialog.show(MyActivity.this, "", "Préparation", true, false);
// Start a new thread that will manage the capture
new ManageCaptureTask().execute(data, c);
}
catch(Exception e){
AlertDialog.Builder dialog = new AlertDialog.Builder(MyActivity.this);
...
dialog.create().show();
}
}
class ManageCaptureTask extends AsyncTask<Object, Void, Boolean> {
protected Boolean doInBackground(Object... args) {
Boolean isSuccess = false;
// initialize the bitmap before the capture
((myApp) getApplication()).setBitmapX(null);
try{
// Check if it is a real device or an emulator
TelephonyManager telmgr = (TelephonyManager) getSystemService(Context.TELEPHONY_SERVICE);
String deviceID = telmgr.getDeviceId();
boolean isEmulator = "000000000000000".equalsIgnoreCase(deviceID);
// get the bitmap
if (isEmulator) {
((myApp) getApplication()).setBitmapX(BitmapFactory.decodeFile(imageFileName));
} else {
((myApp) getApplication()).setBitmapX(BitmapFactory.decodeByteArray((byte[]) args[0], 0, ((byte[])args[0]).length));
}
((myApp) getApplication()).setImageForDB(ImageTools.resizeBmp(((myApp) getApplication()).getBmp()));
// convert the bitmap into a grayscale image and display it in the preview
((myApp) getApplication()).setImage(makeGrayScale());
isSuccess = true;
}
catch (Exception connEx){
errorMessageFromBkgndThread = getString(R.string.errcapture);
}
return isSuccess;
}
protected void onPostExecute(Boolean result) {
// Pass the result data back to the main activity
if (MyActivity.this.pd != null) {
MyActivity.this.pd.dismiss();
}
if (result){
((ImageView) findViewById(R.id.apercu)).setImageBitmap(((myApp) getApplication()).getBmp());
((myApp) getApplication()).setBitmapX(null);
}
else{
// there was an error
ErrAlert();
}
}
}
};
private void ErrAlert(){
// notify the user about the error
AlertDialog.Builder dialog = new AlertDialog.Builder(this);
...
dialog.create().show();
}
}
The activity is terminated on a button click, like this:
Button use = (Button) findViewById(R.id.use);
use.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
Intent intent = new Intent(MyActivity.this, NextActivity.class);
intent.putExtra("dbID", "-1");
intent.putExtra("category", category);
((myApp) getApplication()).setBitmapX(null);
MyActivity.this.startActivity(intent);
MyActivity.this.finish();
}
});
MemoryAnalyzer indicated the memory leak at:
((myApp) getApplication()).setBitmapX(BitmapFactory.decodeByteArray((byte[]) args[0], 0, ((byte[])args[0]).length));
I am grateful for any suggestion, thank you in advance.

Is your thread garbage collected after onPostExecute is called or is it still in the memory?
A Async Task will not be canceled or destroyed at the moment the activity is dismissed. If your thread is more or less lightweight and finishes after a small time, just keep it running and add a MyActivity.this.isFinishing() clause in the onPostExecute() method.
Your Task stores a implicit reference to your Activity MyActivity.this because it is a private class inside the activity. This means that your Activity will not be garbage collected until the task exits.

You can try below code snippet
protected void onPostExecute(Boolean result) {
if(YourActivity.this.isFinished()){
//to smomething here
}
}