单击按钮时，Android Countdown Timer应用程序崩溃

Question

I've just started coding in Android SDK and this is my first attempt at a Countdown Timer. I've set the timer to start at the press of the button with setOnClickListener(). The timer doesn't start but the app stops working when I click the button. The device displays a message saying the app has stopped working.

I've written a method to format the time into minutes and seconds. And i've set the call in the onTick() method of the CountDownTimer.

I've posted my code below. Please take a look and point me to where the problem is and what to do. Much appreciated.

package com.example.day1;

import android.app.Activity;
import android.os.Bundle;
import android.os.CountDownTimer;
import android.view.View;
import android.widget.Button; 
import android.widget.TextView;
public class MainActivity extends Activity {


TextView Timer;//Textview to display the timer
    //This is the method to format the time into minutes and seconds 
public String formatTime(long millis)
{
    String output="00:00";
    long second=millis/1000;
    long minute=second/60;
    second=second%60;
    minute=minute%60;
    String sec=String.valueOf(second);
    String min=String.valueOf(minute);
    output=min+":"+sec;
    return output;
}

@Override
 protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.countdown);
    Timer=(TextView) findViewById(R.id.text1);
    Button button1=(Button)findViewById(R.id.button1);
    button1.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {


    new CountDownTimer(60000,1000)
    {
        public void onTick(long millisUntilFinished){
    Timer.setText(formatTime(millisUntilFinished));
        }
    public void onFinish()
    {
        onStop();
    }
    }.start();
    }
         });
     }
         }

Answer 1

(1) Your app crash because you do not implements your activity with OnClickListener: you need to extend the method of your activity onclicklistener evet

Here is the code

package com.example.day1;

import android.app.Activity;
import android.os.Bundle;
import android.os.CountDownTimer;
import android.view.View;
import android.widget.Button; 
import android.widget.TextView;

///////////////////The solution is fix here///////////////
public class MainActivity extends Activity implements View.OnClickListener {
///////////////////End of solution//////////

TextView Timer;//Textview to display the timer
    //This is the method to format the time into minutes and seconds 
public String formatTime(long millis)
{
    String output="00:00";
    long second=millis/1000;
    long minute=second/60;
    second=second%60;
    minute=minute%60;
    String sec=String.valueOf(second);
    String min=String.valueOf(minute);
    output=min+":"+sec;
    return output;
}

@Override
 protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.countdown);
    Timer=(TextView) findViewById(R.id.text1);
    Button button1=(Button)findViewById(R.id.button1);
    button1.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {


    new CountDownTimer(60000,1000)
    {
        public void onTick(long millisUntilFinished){
    Timer.setText(formatTime(millisUntilFinished));
        }
    public void onFinish()
    {
        onStop();
    }
    }.start();
    }
         });
     }
         }