TimeCount。直接上程式碼。

import android.os.CountDownTimer;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

public class MainActivity extends AppCompatActivity {
    private TimeCount timeCount;
    private Button btn;
    
 
@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        btn = (Button) findViewById(R.id.btn);
        btn.setOnClickListener(new View.OnClickListener() {
            @Override
            
 
public void onClick(View v) {
                //開始倒計時
                timeCount.start();
            }
        });
        initData();
    }
    private void initData() {
        timeCount = new TimeCount(3000, 1000);
    }

    class TimeCount extends CountDownTimer {
        public TimeCount(long millisInFuture, long 
 
countDownInterval) {
            super(millisInFuture, countDownInterval);
        }

        //結束後顯示的文字
        public void onFinish() {
            btn.setText("傳送啟用碼");
            btn.setClickable(true);
        }

        public void onTick(long millisUntilFinished) {
            btn.setClickable(false);
            btn.setText("在" + millisUntilFinished / 1000 + "秒後點擊重發啟用碼");
        }
    }
}