How do we use runOnUiThread in Android

Question

I m new to Android and 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    lt  1000                       btn setText     i                       try                           Thread sleep 300                                              catch  InterruptedException e                            e printStackTrace

User · Answer

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

User · Answer

runOnUiThread new Runnable                     public void run                       Do something on UiThread

User · Answer

Below is corrected Snippet of runThread Function   private void runThread          new Thread             public void run                 while  i    lt  1000                    try                       runOnUiThread new Runnable                               Override                         public void run                                 btn setText       i                                                                         Thread sleep 300                     catch  InterruptedException e                        e printStackTrace                                                    start

User · Answer

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

User · Answer

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

User · Answer

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  lt your runnable gt           this will always be run on the next run loop on the main thread

User · Answer

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

User · Answer

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

User · Answer

If using in fragment then simply write  getActivity   runOnUiThread new Runnable          Override     public void run                Do something on UiThread

User · Answer

This is how I use it   runOnUiThread new Runnable                      Override                 public void run                       Do something on UiThread

User · Answer

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

User · Answer

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

[android] How do we use runOnUiThread in Android?

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