<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"  android:layout_width="match_parent"  android:layout_height="match_parent"  android:orientation="horizontal" >  <Button    android:id="@+id/button"    android:layout_width="wrap_content"    android:layout_height="wrap_content"    android:onClick="clickButton"    android:text="開始計時" /></LinearLayout>

import android.app.Activity;import android.os.Bundle;import android.os.Handler;import android.os.Message;import android.view.View;import android.widget.Button;public class FirstActivity extends Activity{  private Button button;  private int count = 60;  private int COUNT_TIME = 0;  @Override  protected void onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);    setContentView(R.layout.first_activity);    button = (Button) findViewById(R.id.button);  }  private Handler handler = new Handler(){    @Override    public void handleMessage(Message msg) {      if(count <= 0){        count = 60;        button.setText("重新計時");        button.setClickable(true);        return;      }      count--;      button.setText(""+count);      sendEmptyMessageDelayed(COUNT_TIME,1000);    }  };  public void clickButton(View view){    handler.sendEmptyMessage(COUNT_TIME);    button.setClickable(false);  }}

import java.util.Timer;import java.util.TimerTask;import android.app.Activity;import android.os.Bundle;import android.os.Handler;import android.os.Message;import android.view.View;import android.widget.Button;public class FirstActivity extends Activity{  private Button button;  private int count = 30;  private int COUNT_TIME = 0;  @Override  protected void onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);    setContentView(R.layout.first_activity);    button = (Button) findViewById(R.id.button);  }  private Handler handler = new Handler(){    @Override    public void handleMessage(Message msg) {      button.setText(""+count);      if(count <= 0){        count = 30;        button.setClickable(true);        button.setText("重新計時");        timerTask.cancel(); //取消該任務      }    }  };  private Timer timer = new Timer();  private TimerTask timerTask;  public void clickButton(View view){    button.setClickable(false);    timerTask = new TimerTask() {      @Override      public void run() {        count--;        handler.sendEmptyMessage(COUNT_TIME);      }    };    timer.schedule(timerTask,0,1000); //0秒后，每過一秒鐘執行一次該任務  }  @Override  protected void onDestroy() {    super.onDestroy();    //釋放資源    if(timerTask != null){      timerTask.cancel();      timerTask = null;    }    if(timer != null){      timer.cancel();      timer = null;    }  }}

import android.app.Activity;import android.os.Bundle;import android.os.CountDownTimer;import android.view.View;import android.widget.Button;public class FirstActivity extends Activity{  private Button button;  private CountDownTimer timer;  @Override  protected void onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);    setContentView(R.layout.first_activity);    button = (Button) findViewById(R.id.button);  }  public void clickButton(View view){    button.setClickable(false);    //第一個參數：倒計時的毫秒數；第二個參數：接收onTick回調的時間間隔    timer = new CountDownTimer(30000, 10) {       public void onTick(long millisUntilFinished) {         button.setText(millisUntilFinished / 1000 + "秒");       }       public void onFinish() {         button.setText("重新計時");         button.setClickable(true);       }     };    timer.start();  }  @Override  protected void onDestroy() {    super.onDestroy();    if(timer != null){      timer.cancel();    }  }}