AsyncTask

when should we use the AsyncTask?
the task is 2-3 s.
not too log.
can finish before the activity end

If we want some action do in the background for a long time, we should use services.

1.

1.think what is the input of the AsyncTask.eg,int
2. what is the type to indicate the prohress.
3 what do it return.String

2.Create the AsyncTask class

private class MyTask extends AsyncTask<int, Void, String> { ... }

<Params,Progress,Result>

3. implement the method in AsyncTask

1. onPreExecute(), invoked on the UI thread before the task is executed. This step is normally used to setup the task, for instance by showing a progress bar in the user interface.
2. doInBackground(Params...), invoked on the background thread immediately after onPreExecute() finishes executing. This step is used to perform background computation that can take a long time. The parameters of the asynchronous task are passed to this step. The result of the computation must be returned by this step and will be passed back to the last step. This step can also usepublishProgress(Progress...) to publish one or more units of progress. These values are published on the UI thread, in the onProgressUpdate(Progress...) step.
3. onProgressUpdate(Progress...), invoked on the UI thread after a call to publishProgress(Progress...). The timing of the execution is undefined. This method is used to display any form of progress in the user interface while the background computation is still executing. For instance, it can be used to animate a progress bar or show logs in a text field.
4. onPostExecute(Result), invoked on the UI thread after the background computation finishes. The result of the background computation is passed to this step as a parameter.

4.Execute the asynctask

• The task instance must be created on the UI thread.

new MyTask(int i).execute();