How to make a countdown timer in Android?

new CountDownTimer(30000, 1000) {    public void onTick(long millisUntilFinished) {        mTextField.setText("seconds remaining: " + millisUntilFinished / 1000);       //here you can have your logic to set text to edittext    }    public void onFinish() {        mTextField.setText("done!");    }}.start();

Refer to this link.

if you use the below code (as mentioned in accepted answer),

new CountDownTimer(30000, 1000) {    public void onTick(long millisUntilFinished) {        mTextField.setText("seconds remaining: " + millisUntilFinished / 1000);       //here you can have your logic to set text to edittext    }    public void onFinish() {        mTextField.setText("done!");    }}.start();

It will result in memory leak of the instance of the activity where you use this code, if you don't carefully clean up the references.

use the following code

//Declare timerCountDownTimer cTimer = null;//start timer functionvoid startTimer() {    cTimer = new CountDownTimer(30000, 1000) {        public void onTick(long millisUntilFinished) {        }        public void onFinish() {        }    };    cTimer.start();}//cancel timervoid cancelTimer() {    if(cTimer!=null)        cTimer.cancel();}

You need to call cTtimer.cancel() whenever the onDestroy()/onDestroyView() in the owning Activity/Fragment is called.

MainActivity.java

package com.zeustechnocrats.countdown;import android.os.Bundle;import android.os.Handler;import android.support.v7.app.AppCompatActivity;import android.view.View;import android.widget.LinearLayout;import android.widget.TextView;import java.text.SimpleDateFormat;import java.util.Date;public class MainActivity extends AppCompatActivity {    private String EVENT_DATE_TIME = "2021-12-31 10:30:00";    private String DATE_FORMAT = "yyyy-MM-dd HH:mm:ss";    private LinearLayout linear_layout_1, linear_layout_2;    private TextView tv_days, tv_hour, tv_minute, tv_second;    private Handler handler = new Handler();    private Runnable runnable;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.count_down);        initUI();        countDownStart();    }    private void initUI() {        linear_layout_1 = findViewById(R.id.linear_layout_1);        linear_layout_2 = findViewById(R.id.linear_layout_2);        tv_days = findViewById(R.id.tv_days);        tv_hour = findViewById(R.id.tv_hour);        tv_minute = findViewById(R.id.tv_minute);        tv_second = findViewById(R.id.tv_second);    }    private void countDownStart() {        runnable = new Runnable() {            @Override            public void run() {                try {                    handler.postDelayed(this, 1000);                    SimpleDateFormat dateFormat = new SimpleDateFormat(DATE_FORMAT);                    Date event_date = dateFormat.parse(EVENT_DATE_TIME);                    Date current_date = new Date();                    if (!current_date.after(event_date)) {                        long diff = event_date.getTime() - current_date.getTime();                        long Days = diff / (24 * 60 * 60 * 1000);                        long Hours = diff / (60 * 60 * 1000) % 24;                        long Minutes = diff / (60 * 1000) % 60;                        long Seconds = diff / 1000 % 60;                        //                        tv_days.setText(String.format("%02d", Days));                        tv_hour.setText(String.format("%02d", Hours));                        tv_minute.setText(String.format("%02d", Minutes));                        tv_second.setText(String.format("%02d", Seconds));                    } else {                        linear_layout_1.setVisibility(View.VISIBLE);                        linear_layout_2.setVisibility(View.GONE);                        handler.removeCallbacks(runnable);                    }                } catch (Exception e) {                    e.printStackTrace();                }            }        };        handler.postDelayed(runnable, 0);    }    protected void onStop() {        super.onStop();        handler.removeCallbacks(runnable);    }}

activity_main.xml

    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:background="@android:color/white"    android:orientation="horizontal">    <LinearLayout        android:id="@+id/linear_layout_1"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:background="@android:color/black"        android:gravity="center_horizontal"        android:visibility="gone">        <TextView            android:id="@+id/tv_event"            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:layout_margin="20dp"            android:text="Android Event Start"            android:textColor="@android:color/white"            android:textSize="20dp"            android:textStyle="normal" />    </LinearLayout>    <LinearLayout        android:id="@+id/linear_layout_2"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:background="@android:color/black"        android:visibility="visible">        <LinearLayout            android:layout_width="match_parent"            android:layout_height="wrap_content"            android:layout_weight="1"            android:orientation="vertical">            <TextView                android:id="@+id/tv_days"                android:layout_width="wrap_content"                android:layout_height="wrap_content"                android:layout_gravity="center"                android:text="00"                android:textColor="@android:color/white"                android:textSize="20dp"                android:textStyle="bold" />            <TextView                android:id="@+id/tv_days_title"                android:layout_width="wrap_content"                android:layout_height="wrap_content"                android:layout_gravity="center"                android:text="Days"                android:textColor="@android:color/white"                android:textSize="20dp"                android:textStyle="normal" />        </LinearLayout>        <LinearLayout            android:layout_width="match_parent"            android:layout_height="wrap_content"            android:layout_weight="1"            android:orientation="vertical">            <TextView                android:id="@+id/tv_hour"                android:layout_width="wrap_content"                android:layout_height="wrap_content"                android:layout_gravity="center"                android:text="00"                android:textColor="@android:color/white"                android:textSize="20dp"                android:textStyle="bold" />            <TextView                android:id="@+id/tv_hour_title"                android:layout_width="wrap_content"                android:layout_height="wrap_content"                android:layout_gravity="center"                android:text="Hour"                android:textColor="@android:color/white"                android:textSize="20dp"                android:textStyle="normal" />        </LinearLayout>        <LinearLayout            android:layout_width="match_parent"            android:layout_height="wrap_content"            android:layout_weight="1"            android:orientation="vertical">            <TextView                android:id="@+id/tv_minute"                android:layout_width="wrap_content"                android:layout_height="wrap_content"                android:layout_gravity="center"                android:text="00"                android:textColor="@android:color/white"                android:textSize="20dp"                android:textStyle="bold" />            <TextView                android:id="@+id/tv_minute_title"                android:layout_width="wrap_content"                android:layout_height="wrap_content"                android:layout_gravity="center"                android:text="Minute"                android:textColor="@android:color/white"                android:textSize="20dp"                android:textStyle="normal" />        </LinearLayout>        <LinearLayout            android:layout_width="match_parent"            android:layout_height="wrap_content"            android:layout_weight="1"            android:orientation="vertical">            <TextView                android:id="@+id/tv_second"                android:layout_width="wrap_content"                android:layout_height="wrap_content"                android:layout_gravity="center"                android:text="00"                android:textColor="@android:color/white"                android:textSize="20dp"                android:textStyle="bold" />            <TextView                android:id="@+id/tv_second_title"                android:layout_width="wrap_content"                android:layout_height="wrap_content"                android:layout_gravity="center"                android:text="Second"                android:textColor="@android:color/white"                android:textSize="20dp"                android:textStyle="normal" />        </LinearLayout>    </LinearLayout></LinearLayout>