Develop Reference

Best way handle result from thread on UI

I want to save data to DB in new Thread and after that show toast on the UI.
Method for saving:
public void addToBasket(String text) {
new Thread(() -> {
//emulate save
try {
Thread.sleep(5000L);
} catch (InterruptedException e) {
e.printStackTrace();
}
//after that I need say ti UI thread - show Toast!
}).start();
}
I call this method:
BasketService.me().addToBasket(result.getContents());
I do now want use AsyncTask for this. Please tell me the best way to implement such tasks

batter to use:
runOnUiThread(new Runnable() {
public void run() {
//Do what ever you want do man
}
});
runOnUiThread() method to manipulate your UserInterface from background threads.

In case of callback from a nonUi thread to Ui thread you can use runOnUiThread()(As specified above) or Handler. Below is a example of using handler.
protected static final Handler mainThreadHandler = new Handler(Looper.getMainLooper());
protected void onSuccessInMainThread(final R result, final Bundle bundle) {
mainThreadHandler.post(new Runnable() {
#Override
public void run() {
callback.onSuccess(result, bundle);
}
});
}
protected void onErrorInMainThread(final Exception error) {
mainThreadHandler.post(new Runnable() {
#Override
public void run() {
callback.onError(error);
}
});
}

How to execute an instruction/method immediately after ProgressDialog dismisses?

I am trying to execute the method doSomeWork(); after the ProgressDialog dismisses in my method printing();which seems to be overlapped by the other method and the dialog is not showed up. If I comment method doSomeWork(); the dialog is displayed correctly until the thread is finished.
Here is my method printing();
public void printing()
{
final ProgressDialog printingDialog = ProgressDialog.show(this, "Printing...", "Please wait", true, false);
new Thread(new Runnable() {
#Override
public void run()
{
//something big executing here
}
}).start();
}
He is my method doSomework():
public void doSomeWork(){
Thread receiptPrint = new Thread(new Runnable() {
#Override
public void run() {
//something here
runOnUiThread(new Runnable() {
#Override
public void run() {
//another dialog here
}
});
}
});
}
Here you can see the how I am calling those two methods:
private OnClickListener onClickPrint = new OnClickListener() {
public void onClick(final View v) {
Log.d("Button","Clicked on Print Order Button");
printing();
doSomeWork();
Does anyone know how could I execute doSomeWork() only when printing(); will be completely finished?

This is one of the purposes of an AsyncTask. It would look similar to this:
public void onClick(final View v) {
new AsyncTask<Void, Void, Void>() {
#Override
protected void onPreExecute() {
//Show your progress dialog in here
super.onPreExecute();
}
#Override
protected Void doInBackground( Void... params ) {
printing();
return null;
}
#Override
protected void onPostExecute( Void result ) {
//Dismiss your progress dialog here
doSomeWork();
}
}.execute();
}

Instead of using thread you can use asynchronous task. Show the progress dialog in the preexecute method call the printing method inside the background method after completing printing operation call the doSomeWork() inside the postexecute method.

You can use Handler for that in android. for example consider the following piece of code. you can dismiss the dialogs inside handlers. may it work for you.
private void printing(){
Thread receiptPrint = new Thread(new Runnable() {
#Override
public void run() {
retrieveEmails();
runOnUiThread(new Runnable() {
#Override
public void run() {
try{
//here your code executes
//after code executes do following:
uiHandler.sendEmptyMessage(0);
}catch(Exception ex){
errorHandler.sendEmptyMessage(0);
}
}
});
}
});
receiptPrint.start();
}
final Handler uiHandler = new Handler() {
#Override
public void handleMessage(Message msg) {
//here execute doSomeWork()
}
};
final Handler errorHandler = new Handler() {
#Override
public void handleMessage(Message msg) {
//do other stuff
}
};

Progressdialog won't show up

I want to show this dialog, while the thread tries to build up a connection, but the dialog will not show up when I press the button which starts this method.
public void add_mpd(View view) {
dialog = ProgressDialog.show(MainActivity.this, "", "Trying to connect...");
new Thread(new Runnable() {
public void run() {
try {
String child;
EditText new_mpd = (EditText) findViewById(R.id.new_mpd);
child = new_mpd.getText().toString();
mpd = new MPD(child);
children.get(1).add(child);
} catch (UnknownHostException e) {
e.printStackTrace();
} catch (MPDConnectionException e) {
e.printStackTrace();
}
}
}
).start();
adapter.notifyDataSetChanged();
dialog.dismiss();
}

It will not show up because the (blocking) work is done in another thread. That means, the start()-method of the Thread-class will not block.
Ergo, you show the Dialog, the Thread is started and the dialog is immediately dismissed (and therefore closed).
Put the call to dismiss() at the end of your run()-method and it should work just fine.
The above might be working for you, but you should not use the Thread-class directly. There are wrappers around it which are way more comfortable to use.
In Android, if you want to do long-term work off the UI-Thread, you should use an AsyncTask.

Additionaly, to build up on what Lukas said, you can look at this example.
http://www.helloandroid.com/tutorials/using-threads-and-progressdialog
public class ProgressDialogExample extends Activity implements Runnable {
private String pi_string;
private TextView tv;
private ProgressDialog pd;
#Override
public void onCreate(Bundle icicle) {
super.onCreate(icicle);
setContentView(R.layout.main);
tv = (TextView) this.findViewById(R.id.main);
tv.setText("Press any key to start calculation");
}
#Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
pd = ProgressDialog.show(this, "Working..", "Calculating Pi", true,
false);
Thread thread = new Thread(this);
thread.start();
return super.onKeyDown(keyCode, event);
}
public void run() {
pi_string = Pi.computePi(800).toString();
handler.sendEmptyMessage(0);
}
private Handler handler = new Handler() {
#Override
public void handleMessage(Message msg) {
pd.dismiss();
tv.setText(pi_string);
}
};
}

How do we use runOnUiThread in Android?

I'm trying to use the UI-Thread, so I've written a simple test activity. But I think I've misunderstood something, because on clicking the button - the app does not respond anymore
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(){
runOnUiThread (new Thread(new Runnable() {
public void run() {
while(i++ < 1000){
btn.setText("#"+i);
try {
Thread.sleep(300);
}
catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}));
}
}

Below is corrected Snippet of runThread Function.
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();
}

Just wrap it as a function, then call this function from your background thread.
public void debugMsg(String msg) {
final String str = msg;
runOnUiThread(new Runnable() {
#Override
public void run() {
mInfo.setText(str);
}
});
}

You have it back-to-front. Your button click results in a call to runOnUiThread(), but this isn't needed, since the click handler is already running on the UI thread. Then, your code in runOnUiThread() is launching a new background thread, where you try to do UI operations, which then fail.
Instead, just launch the background thread directly from your click handler. Then, wrap the calls to btn.setText() inside a call to runOnUiThread().

runOnUiThread(new Runnable() {
public void run() {
//Do something on UiThread
}
});

There are several techniques using of runOnUiThread(), lets see all
This is my main thread (UI thread) called AndroidBasicThreadActivity and I'm going to update it from a worker thread in various ways -
public class AndroidBasicThreadActivity extends AppCompatActivity
{
public static TextView textView;
#Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_android_basic_thread);
textView = (TextView) findViewById(R.id.textview);
MyAndroidThread myTask = new MyAndroidThread(AndroidBasicThreadActivity.this);
Thread t1 = new Thread(myTask, "Bajrang");
t1.start();
}
}
1.) By passing Activity's instance as an argument on worker thread
class MyAndroidThread implements Runnable
{
Activity activity;
public MyAndroidThread(Activity activity)
{
this.activity = activity;
}
#Override
public void run()
{
//perform heavy task here and finally update the UI with result this way -
activity.runOnUiThread(new Runnable()
{
#Override
public void run()
{
AndroidBasicThreadActivity.textView.setText("Hello!! Android Team :-) From child thread.");
}
});
}
}
2.) By using View's post(Runnable runnable) method in worker thread
class MyAndroidThread implements Runnable
{
Activity activity;
public MyAndroidThread(Activity activity)
{
this.activity = activity;
}
#Override
public void run()
{
//perform heavy task here and finally update the UI with result this way -
AndroidBasicThreadActivity.textView.post(new Runnable()
{
#Override
public void run()
{
AndroidBasicThreadActivity.textView.setText("Hello!! Android Team :-) From child thread.");
}
});
}
}
3.) By using Handler class from android.os package
If we don't have the context (this/ getApplicationContext()) or Activity's instance (AndroidBasicThreadActivity.this) then we have to use Handler class as below -
class MyAndroidThread implements Runnable
{
Activity activity;
public MyAndroidThread(Activity activity)
{
this.activity = activity;
}
#Override
public void run()
{
//perform heavy task here and finally update the UI with result this way -
new Handler(Looper.getMainLooper()).post(new Runnable() {
public void run() {
AndroidBasicThreadActivity.textView.setText("Hello!! Android Team :-) From child thread.");
}
});
}
}

If using in fragment then simply write
getActivity().runOnUiThread(new Runnable() {
#Override
public void run() {
// Do something on UiThread
}
});

We use Worker Thread to make Apps smoother and avoid ANR's. We may need to update UI after the heavy process in worker Tread.
The UI can only be updated from UI Thread. In such cases, we use Handler or runOnUiThread both have a Runnable run method that executes in UI Thread.
The onClick method runs in UI thread so don't need to use runOnUiThread here.
Using Kotlin
While in Activity,
this.runOnUiThread {
// Do stuff
}
From Fragment,
activity?.runOnUiThread {
// Do stuff
}
Using Java,
this.runOnUiThread(new Runnable() {
void run() {
// Do stuff
}
});

For fragment use that:
requireActivity().runOnUiThread(() -> {
//your code logic
});
For activity use that:
runOnUiThread(() -> {
//your code logic
});
runOnUiThread is used in a way the UI can be updated with our background thread. For more: https://www.tutorialspoint.com/how-do-we-use-runonuithread-in-android

thy this:
#UiThread
public void logMsg(final String msg) {
new Handler(Looper.getMainLooper()).post(new Runnable() {
#Override
public void run() {
Log.d("UI thread", "I am the UI thread");
}
});
}

You can use from this sample :
In the following example, we are going to use this facility to publish the result from a
synonym search that was processed by a background thread.
To accomplish the goal during the OnCreate activity callback, we will set up
onClickListener to run searchTask on a created thread.
When the user clicks on the Search button, we will create a Runnable anonymous
class that searches for the word typed in R.id.wordEt EditText and starts the
thread to execute Runnable.
When the search completes, we will create an instance of Runnable SetSynonymResult
to publish the result back on the synonym TextView over the UI thread.
This technique is sometime not the most convenient one, especially when we don't
have access to an Activity instance; therefore, in the following chapters, we are
going to discuss simpler and cleaner techniques to update the UI from a background
computing task.
public class MainActivity extends AppCompatActivity {
class SetSynonymResult implements Runnable {
String synonym;
SetSynonymResult(String synonym) {
this.synonym = synonym;
}
public void run() {
Log.d("AsyncAndroid", String.format("Sending synonym result %s on %d",
synonym, Thread.currentThread().getId()) + " !");
TextView tv = (TextView) findViewById(R.id.synonymTv);
tv.setText(this.synonym);
}
}
;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button search = (Button) findViewById(R.id.searchBut);
final EditText word = (EditText) findViewById(R.id.wordEt);
search.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Runnable searchTask = new Runnable() {
#Override
public void run() {
String result = searchSynomim(word.getText().toString());
Log.d("AsyncAndroid", String.format("Searching for synonym for %s on %s",
word.getText(), Thread.currentThread().getName()));
runOnUiThread(new SetSynonymResult(result));
}
};
Thread thread = new Thread(searchTask);
thread.start();
}
});
}
static int i = 0;
String searchSynomim(String word) {
return ++i % 2 == 0 ? "fake" : "mock";
}
}
Source :
asynchronous android programming Helder Vasconcelos

This is how I use it:
runOnUiThread(new Runnable() {
#Override
public void run() {
//Do something on UiThread
}
});

#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
gifImageView = (GifImageView) findViewById(R.id.GifImageView);
gifImageView.setGifImageResource(R.drawable.success1);
new Thread(new Runnable() {
#Override
public void run() {
try {
//dummy delay for 2 second
Thread.sleep(8000);
} catch (InterruptedException e) {
e.printStackTrace();
}
//update ui on UI thread
runOnUiThread(new Runnable() {
#Override
public void run() {
gifImageView.setGifImageResource(R.drawable.success);
}
});
}
}).start();
}

Try this: getActivity().runOnUiThread(new Runnable...
It's because:
1) the implicit this in your call to runOnUiThread is referring to AsyncTask, not your fragment.
2) Fragment doesn't have runOnUiThread.
However, Activity does.
Note that Activity just executes the Runnable if you're already on the main thread, otherwise it uses a Handler. You can implement a Handler in your fragment if you don't want to worry about the context of this, it's actually very easy:
// A class instance
private Handler mHandler = new Handler(Looper.getMainLooper());
// anywhere else in your code
mHandler.post(<your runnable>);
// ^ this will always be run on the next run loop on the main thread.

How to sync between ProgressDialog and text appearance?

i got this progress dialog code:
new Thread() {
#Override
public void run() {
try {
sleep(1000);
}
catch (Exception e) {
Log.e("tag", e.getMessage());
}
// dismiss the progress dialog
progressDialog.dismiss();
}
}.start();
and i got text that will apear after some httprequest actions:
editText2.setText(stringEr);
how do i sync between them? i want that the text will be hidden untill the progress will finish
tnx!

You have to use Handlers to update your UI. A little modification here,
new Thread()
{
#Override
public void run()
{
try
{
//Instead of sleep, call your http request method here.
handler.sendEmptyMessage(0);
}
catch (Exception e)
{
Log.e("tag", e.getMessage());
}
// dismiss the progress dialog
progressDialog.dismiss();
}
}.start();
And create a handler in onCreate(),
Handler handler=new Handler()
{
public void handleMEssage(Message msg)
{
if(msg.what==0)
editText2.setText(stringEr);
}
};

i think you should use AsyncTask for that and you can hide in OnPreExecute Method i mean when asynctask in started and show in OnPostExecute method. after complete the progress.

Android skip the painful Threading concept, Use Asyntask class.
http://developer.android.com/reference/android/os/AsyncTask.html
private class UIOperation extends AsyncTask<String, Void, String> {
#Override
protected void onPreExecute() {
//show dialog
}
#Override
protected String doInBackground(String... params) {
//collect data
return null;
}
#Override
protected void onPostExecute(String result) {
//dismiss dialog
//update UI
}
}