totalcross.util.concurrent

Class AsyncTask<Params,Progress,Result>

java.lang.Object

totalcross.util.concurrent.AsyncTask<Params,Progress,Result>

Type Parameters:

Params -

Progress -

Result -

public abstract class AsyncTask<Params,Progress,Result>
extends java.lang.Object

AsyncTask provides use of asynchronous operations without ocupying UI Thread with non user interface tasks. In addition, you can easily publish results without the need of manupulating Thread, see the example bellow (Copy and paste this code inside a Container instance):

 Button dldButton = new Button("download zip");
 add(dldButton, CENTER, CENTER);

 final ProgressBar progressBar = new ProgressBar();
 add(progressBar, CENTER, AFTER + UnitsConverter.toPixels(DP + 16),
         PARENTSIZE + 80, PREFERRED);

 dldButton.addPressListener((c) -> {
     new AsyncTask() {
         int progress = 0;
         UpdateListener updateListener = null;

         @Override
         protected Object doInBackground(Object... objects) {
             HttpStream.Options o = new HttpStream.Options();
             o.httpType = HttpStream.GET;
             final String url = "";

             if(url.startsWith("https:"))
                 o.socketFactory = new SSLSocketFactory();

             try {
                 HttpStream p = new HttpStream(new URI(url));
                 File f = new File("file.zip", File.CREATE_EMPTY);
                 int totalSize = p.contentLength;
                 byte [] buff = new  byte[4096];
                 BufferedStream bs = new BufferedStream(f, BufferedStream.WRITE, 4096);
                 int counter = 0;
                 while(true) {
                     int size = p.readBytes(buff, 0, buff.length);
                     counter += size;
                     progress = (int)((counter/(double)totalSize)*100);
                     if(size <= 0) break;
                     bs.writeBytes(buff, 0, size);
                 }
                 progress = 100;
                 bs.close();
                 p.close();
                 f.close();
             } catch (IOException e) {
                 e.printStackTrace();
             }
             return null;
         }

         @Override
         protected void onPreExecute() {
             dldButton.setEnabled(false);
             MainWindow.getMainWindow().addUpdateListener(updateListener = (elapsed) -> {
                 progressBar.setValue(progress);
             });
         }

         @Override
         protected void onPostExecute(Object result) {
             dldButton.setEnabled(true);
             MainWindow.getMainWindow().removeUpdateListener(updateListener);
         }
     }.execute();
 });

 

Since:

TotalCross 4.3.9

Constructor Summary

Constructors

Constructor and Description
AsyncTask()

Method Summary

Modifier and Type	Method and Description
protected abstract Result	doInBackground(Params... params) Method in background thread when execute method is called
AsyncTask<Params,Progress,Result>	execute(Params... params) execute doInBackground(java.lang.Object[]) outside UI Thread
protected void	onPostExecute(Result result) Method called in UI Thread when the task executed in doInBackground(java.lang.Object[]) is finished.
protected void	onPreExecute() Process task on pre execute in the thread in which this method was called
protected void	onProgressUpdate(Progress... values) Override this method if you want to Provide progress to the UI Thread when calling publishProgress inside doInBackground.
protected void	publishProgress(Progress... values) Calls onProgressUpdate(java.lang.Object[]) in UI Thread

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

AsyncTask

public AsyncTask()

Method Detail

onPreExecute

protected void onPreExecute()

Process task on pre execute in the thread in which this method was called

doInBackground

protected abstract Result doInBackground(Params... params)

Method in background thread when execute method is called

Parameters:

params -

Returns:

See Also:

execute(java.lang.Object[])

onProgressUpdate

protected void onProgressUpdate(Progress... values)

Override this method if you want to Provide progress to the UI Thread when calling publishProgress inside doInBackground.

Parameters:

values -

See Also:

doInBackground(java.lang.Object[]), publishProgress(java.lang.Object[])

publishProgress

@SafeVarargs
protected final void publishProgress(Progress... values)

Calls onProgressUpdate(java.lang.Object[]) in UI Thread

Parameters:

values -

See Also:

onProgressUpdate(java.lang.Object[])

onPostExecute

protected void onPostExecute(Result result)

Method called in UI Thread when the task executed in doInBackground(java.lang.Object[]) is finished.

Parameters:

result -

See Also:

doInBackground(java.lang.Object[])

execute

@SafeVarargs
public final AsyncTask<Params,Progress,Result> execute(Params... params)

execute doInBackground(java.lang.Object[]) outside UI Thread

Parameters:

params -

Returns: