Android中实现计时器的小案例

在android中实现倒计时的功能

实验效果：

（1）activity_main.xml文件中具体代码如下：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="bzu.edu.cn.mytimer.MainActivity">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="10"
        android:textSize="100sp"
        android:id="@+id/tvNumber"
        android:layout_centerVertical="true"
        android:layout_centerHorizontal="true" />
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="start"
        android:background="@null"
        android:layout_below="@+id/tvNumber"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="29dp"
        android:onClick="start"
        android:id="@+id/button"/>
</RelativeLayout>

（2）MainActivity中具体代码如下：

package bzu.edu.cn.mytimer;

import android.os.Handler;
import android.os.Message;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {
    private TextView tvNumber;
    private int count=10;
    private static final int UPDATE_TIME=1;
    private Handler handler=new Handler(){
        public void handleMessage(Message msg){
            super.handleMessage(msg);
            switch (msg.what){
                case UPDATE_TIME:tvNumber.setText(count+"");
            }
        }
    };
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        tvNumber=(TextView)findViewById(R.id.tvNumber);
    }
    public void start(View view){
        new Thread(new Runnable() {
            @Override
            public void run() {
                while(count>0){
                    count--;
                    Message message=new Message();
                    message.what=UPDATE_TIME;
                    handler.sendMessage(message);
                    try {
                        Thread.sleep(1000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }

                }
            }
        }).start();
    }
}