Android asyncTask details

Android AsyncTask is a lightweight asynchronous task processing class

Common steps->Create an asynchronous task processing class inherited from the AsyncTask class

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(AsyncTask

Params to start the task execution input parameters, such as a set of URLs

Progress background task execution percentage

Result The return result after the task is executed)

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class MyAsyncTask extends AsyncTask {



 @Override

 protected String doInBackground(Integer... params) {

 //Run on worker thread

 //Execute immediately after the onPreExecute method is executed, responsible for execution

 // Time-consuming background processing tasks, you can call the publishProgress method to implement

 //Update task progress at the time

}



 @Override

 protected void onPreExecute() {

 //Run on UI thread

 //Before performing background time-consuming operations, it is usually used for some Initialization operations, such as progress bar display

}



 @Override

 protected void onProgressUpdate(Integer... values) {

 //Run on UI thread

 //In the doBackground method, it will be triggered every time the publishProgress method is called The method

}

}

->Create an instance of MyAsyncTask in the UI thread

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->Call mAsyncTask.execute() in the UI thread

A complete example

MainActivity

package com.example.myfirstapp;



import androidx.appcompat.app.AppCompatActivity;



import android.os.AsyncTask;

import android.os.Bundle;

import android.view.View;

import android.widget.Button;

import android.widget.ProgressBar;

import android.widget.TextView;



public class MainActivity extends AppCompatActivity {



 private TextView txttitle;

 private ProgressBar pgbar;

 private Button btnupdate;



 @Override

 protected void onCreate(Bundle savedInstanceState) {

 super.onCreate(savedInstanceState);

 setContentView(R.layout.activity_main);

 txttitle = (TextView)findViewById(R.id.txttitle);

 pgbar = (ProgressBar)findViewById(R.id.pgbar);

 btnupdate = (Button)findViewById(R.id.btnupdate);

 btnupdate.setOnClickListener(new View.OnClickListener() {

 @Override

 public void onClick(View v) {

 MyAsyncTask myTask = new MyAsyncTask(txttitle,pgbar);

 myTask.execute(1000);

}

 });

}

}



class DelayOperator {

 // Delayed operation to simulate downloading

 public void delay()

 {

 try {

 Thread.sleep(1000);

 }catch (InterruptedException e){

 e.printStackTrace();;

}

}

}



class MyAsyncTask extends AsyncTask

{

 private TextView txt;

 private ProgressBar pgbar;



 public MyAsyncTask(TextView txt,ProgressBar pgbar)

 {

 super();

 this.txt = txt;

 this.pgbar = pgbar;

}





 //This method does not run in the UI thread, mainly used Asynchronous operation, by calling publishProgress() method

 // trigger onProgressUpdate to operate on the UI

 @Override

 protected String doInBackground(Integer... params) {

 DelayOperator dop = new DelayOperator();

 int i = 0;

 for (i = 10;i <= 100;i+=10 )

 {

 dop.delay();

 publishProgress(i);

}

 //i + params[0].intValue() span>

 return "";

}



 //This method runs in the UI thread and can be used for UI controls Make settings

 @Override

 protected void onPreExecute() {

 txt.setText("Start executing asynchronous thread~");

}





 //In the doBackground method, it will be triggered every time the publishProgress method is called this method

 // runs in the UI thread and can operate on UI controls 





 @Override

 protected void onProgressUpdate(Integer... values) {

 pgbar.setProgress(values[0].intValue());

}

}

Layout code

activity_main

class MyAsyncTask extends AsyncTask {



 @Override

 protected String doInBackground(Integer... params) {

 //Run on worker thread

 //Execute immediately after the onPreExecute method is executed, responsible for execution

 // Time-consuming background processing tasks, you can call the publishProgress method to implement

 //Update task progress at the time

}



 @Override

 protected void onPreExecute() {

 //Run on UI thread

 //Before performing background time-consuming operations, it is usually used for some Initialization operations, such as progress bar display

}



 @Override

 protected void onProgressUpdate(Integer... values) {

 //Run on UI thread

 //In the doBackground method, it will be triggered every time the publishProgress method is called The method

}

}

package com.example.myfirstapp;



import androidx.appcompat.app.AppCompatActivity;



import android.os.AsyncTask;

import android.os.Bundle;

import android.view.View;

import android.widget.Button;

import android.widget.ProgressBar;

import android.widget.TextView;



public class MainActivity extends AppCompatActivity {



 private TextView txttitle;

 private ProgressBar pgbar;

 private Button btnupdate;



 @Override

 protected void onCreate(Bundle savedInstanceState) {

 super.onCreate(savedInstanceState);

 setContentView(R.layout.activity_main);

 txttitle = (TextView)findViewById(R.id.txttitle);

 pgbar = (ProgressBar)findViewById(R.id.pgbar);

 btnupdate = (Button)findViewById(R.id.btnupdate);

 btnupdate.setOnClickListener(new View.OnClickListener() {

 @Override

 public void onClick(View v) {

 MyAsyncTask myTask = new MyAsyncTask(txttitle,pgbar);

 myTask.execute(1000);

}

 });

}

}



class DelayOperator {

 // Delayed operation to simulate downloading

 public void delay()

 {

 try {

 Thread.sleep(1000);

 }catch (InterruptedException e){

 e.printStackTrace();;

}

}

}



class MyAsyncTask extends AsyncTask

{

 private TextView txt;

 private ProgressBar pgbar;



 public MyAsyncTask(TextView txt,ProgressBar pgbar)

 {

 super();

 this.txt = txt;

 this.pgbar = pgbar;

}





 //This method does not run in the UI thread, mainly used Asynchronous operation, by calling publishProgress() method

 // trigger onProgressUpdate to operate on the UI

 @Override

 protected String doInBackground(Integer... params) {

 DelayOperator dop = new DelayOperator();

 int i = 0;

 for (i = 10;i <= 100;i+=10 )

 {

 dop.delay();

 publishProgress(i);

}

 //i + params[0].intValue() span>

 return "";

}



 //This method runs in the UI thread and can be used for UI controls Make settings

 @Override

 protected void onPreExecute() {

 txt.setText("Start executing asynchronous thread~");

}





 //In the doBackground method, it will be triggered every time the publishProgress method is called this method

 // runs in the UI thread and can operate on UI controls 





 @Override

 protected void onProgressUpdate(Integer... values) {

 pgbar.setProgress(values[0].intValue());

}

}

<LinearLayout xmlns:android="http://schemas.android.com/ apk/res/android"

 xmlns:tools="http://schemas.android.com/tools"

 android:layout_width="match_parent"

 android:layout_height="match_parent"

 android:orientation="vertical"

 tools:context=".MyActivity">

 <TextView

 android:id="@+id/txttitle"

 android:layout_width="wrap_content"

 android:layout_height="wrap_content" />

 

 <ProgressBar

 android:layout_width="fill_parent"

 android:layout_height="wrap_content"

 android:id="@+id/pgbar"

 style="?android:attr/progressBarStyleHorizontal"/>

 <Button

 android:layout_width="wrap_content"

 android:layout_height="wrap_content"

 android:id="@+id/btnupdate"

 android:text="Update progressBar"/>

LinearLayout>