Posts tagged have-the-same

This exercise have the same effect of “Android background thread, by extending Thread” and “Android background thread, by implementing Thread object, provided with a Runnable object“. It is implemented in AsyncTask instead of Thread.

AsyncTask enables proper and easy use of the UI thread. This class allows to perform background operations and publish results on the UI thread without having to manipulate threads and/or handlers.

An asynchronous task is defined by a computation that runs on a background thread and whose result is published on the UI thread. An asynchronous task is defined by 3 generic types, called Params, Progress and Result, and 4 steps, called begin, doInBackground, processProgress and end.

main.xml

AndroidBackgroundAsyncTask.java

package com.exercise.AndroidBackgroundAsyncTask;

import android.app.Activity;import android.os.AsyncTask;import android.os.Bundle;import android.os.SystemClock;import android.view.View;import android.widget.TextView;import android.widget.Toast;

public class AndroidBackgroundAsyncTask extends Activity {

 TextView myText;

   public class BackgroundAsyncTask extends   AsyncTask {

    boolean myTextOn;

  @Override  protected Void doInBackground(Void... params) {   // TODO Auto-generated method stub

   while(true)   {    myTextOn = !myTextOn;    publishProgress(myTextOn);     SystemClock.sleep(1000);   }   //return null;  }

  @Override  protected void onPostExecute(Void result) {   // TODO Auto-generated method stub   //it will never been shown in this exercise...   Toast.makeText(AndroidBackgroundAsyncTask.this,     "onPostExecute", Toast.LENGTH_LONG).show();  }

  @Override  protected void onPreExecute() {   // TODO Auto-generated method stub   myTextOn = true;   Toast.makeText(AndroidBackgroundAsyncTask.this,     "onPreExecute", Toast.LENGTH_LONG).show();  }

  @Override  protected void onProgressUpdate(Boolean... values) {   // TODO Auto-generated method stub

   if (values[0]){    myText.setVisibility(View.GONE);    }   else{    myText.setVisibility(View.VISIBLE);    }   }

 }

 /** Called when the activity is first created. */   @Override   public void onCreate(Bundle savedInstanceState) {       super.onCreate(savedInstanceState);       setContentView(R.layout.main);       myText = (TextView)findViewById(R.id.mytext);

       new BackgroundAsyncTask().execute();   }}

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