CountDownTimer

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/LinearLayout2"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context="${relativePackage}.${activityClass}" >

    <TextView
        android:id="@+id/textView1"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:gravity="center"
        android:text="5"
        android:textSize="140sp" />

    <ImageView
        android:id="@+id/imageView1"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:src="@drawable/ic_launcher" />

</LinearLayout>

package com.example.app24;

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

public class MainActivity extends Activity {

    CountDownTimer timer;
    TextView textView1;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        textView1 = (TextView)this.findViewById(R.id.textView1);

        timer=new CountDownTimer(5000,10) {

            @Override
            public void onTick(long millisUntilFinished) {
                // TODO Auto-generated method stub
                Log.e("MainActivity", "經過時間:"+millisUntilFinished);
                textView1.setText(""+millisUntilFinished/1000);
            }

            @Override
            public void onFinish() {
                Log.e("MainActivity","時間到");
                textView1.setVisibility(View.GONE);
            }
        };
        timer.start();
    }
}