Thread In Android @ Worker and Main Thread - Communication

Hi .... Dear All ....  Today I am uploading a superb example of Multi-threading. 

In this example i have one Main Thread / UI Thread and worker thread.

Worker thread updates the status on UI thread.

•    Threads are lightweight processes, which allow us to perform jobs in parallel and concurrent manner.

•      Android starts a process with a single thread for execution called the “Main thread” or “UI Thread”.

•       Capable of handling multiple threads

•       Different threads need different priorities

Thread Life Cycle

In Android we can classify threads based on their Access to UI toolkit. Thus we have two types of thread

  1. UI thread

  2. Worker thread

UI thread

•We have already seen that the application starts its execution with a single thread called the UI thread.

•Since the UI thread is responsible for the user’s interaction with the UI components.

•Android UI toolkit is not thread safe. This means that other thread cannot access the UI toolkit.

•In order to manipulate the widgets, we must follow these two golden rules.

  • Always access the UI toolkit from the UI thread only.

  • Never block the UI thread

Worker Thread

•Worker threads are created to remove long time-consuming jobs off from the UI thread.

•These threads are vital for the responsiveness of the application, given that UI thread can’t be blocked.

•Basically, all network related operations like fetching data from web services, downloading files, etc., database queries, IO operations like reading or writing to a file, time consuming calculations etc. are performed on these threads.

•To overcome this problem, Android has a work around solution allows us to post task to the UI thread from any thread. Following are the method which helps us achieve this.

  • View.post(Runnable)

  • Activity.runOnUiThread(Runnable)

  • View.postDelayed(Runnable,timeInMillis) 

See an Example 

A. Output will be like 

a.

b.

B. XML files are 

<?xml version="1.0" encoding="utf-8"?>

<RelativeLayout 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"

    tools:context=".ThreadActivity">

    <TextView        android:id="@+id/counter"

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:textSize="40dp"

        android:layout_centerVertical="true"

        android:layout_alignParentEnd="true"

        android:textAlignment="center"/>

</RelativeLayout>

C. Java code is as 

package com.exam.ravi.threadex1;

import android.os.SystemClock;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.TextView;

public class ThreadActivity extends AppCompatActivity {
     TextView textView;
    @Override    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_thread);
        textView = (TextView) findViewById(R.id.counter);
        new Thread(new Runnable() {
            @Override            public void run() {
           int i=0;
                while(i<100)
                {
                    SystemClock.sleep(200);
                    i++;
                    final int curCount =i;
                    if(curCount%10==0)
                    {
                        textView.post(new Runnable() {
                            @Override                            public void run() {
                                textView.setText(curCount+"% Complete");
                            }
                        });
                    }
                }
                textView.post(new Runnable() {
                    @Override                    public void run() {
                        textView.setText("Count Completed");
                    }
                });
            }
        }).start();
    }
}