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copied!<p>Ok you are trying to access the GUI via another thread. This, in the main, is not good practice. </p> <p>The AsyncTask executes everything in <code>doInBackground()</code> inside of another thread, which does not have access to the GUI where your views are.</p> <p><code>preExecute()</code> and <code>postExecute()</code> offer you access to GUI before and after the heavy lifting occurs in this new thread, you can even pass the result of the long operation to <code>postExecute()</code> to then show any results of processing.</p> <p>See these lines where you are later updating your TextView:</p> <pre><code>TextView txt = (TextView) findViewById(R.id.output); txt.setText("Executed"); </code></pre> <p>put them in <code>PostExecute()</code></p> <p>You will then see your TextView text updated after the <code>doInBackground</code> completes.</p> <p><strong>EDIT:</strong> I noticed that your onClick listener does not check to see which View has been selected. I find the easiest way to do this is via switch statements. I have a complete class edited below with all suggestions to save confusion.</p> <pre><code>import android.app.Activity; import android.os.AsyncTask; import android.os.Bundle; import android.provider.Settings.System; import android.view.View; import android.widget.Button; import android.widget.TextView; import android.view.View.OnClickListener; public class AsyncTaskActivity extends Activity implements OnClickListener { Button btn; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); btn = (Button) findViewById(R.id.button1); // because we implement OnClickListener we only have to pass "this" // (much easier) btn.setOnClickListener(this); } public void onClick(View view) { // detect the view that was "clicked" switch (view.getId()) { case R.id.button1: new LongOperation().execute(""); break; } } private class LongOperation extends AsyncTask<String, Void, String> { @Override protected String doInBackground(String... params) { for (int i = 0; i < 5; i++) { try { Thread.sleep(1000); } catch (InterruptedException e) { Thread.interrupted(); } } return "Executed"; } @Override protected void onPostExecute(String result) { TextView txt = (TextView) findViewById(R.id.output); txt.setText("Executed"); // txt.setText(result); // might want to change "executed" for the returned string passed // into onPostExecute() but that is upto you } @Override protected void onPreExecute() {} @Override protected void onProgressUpdate(Void... values) {} } } </code></pre>

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