android实现倒计时功能（开始、暂停、0秒结束）

<Button   android:id="@+id/button_start_timer"   android:layout_width="0dp"   android:layout_height="wrap_content"   android:layout_weight="1"   android:layout_gravity="center_vertical"   android:gravity="center"   android:text="开始"   android:textSize="12sp"   /><TextView   android:id="@+id/textViewTime24"   android:layout_width="0dp"   android:layout_height="wrap_content"   android:layout_gravity="center_vertical"   android:layout_weight="2"   android:gravity="center"   android:text="24"   android:textColor="#33ff00"   android:textSize="60sp" />

package com.example.wlf.gamerecorder.gameon;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.view.View;import android.widget.Button;import android.widget.TextView;import android.os.Handler;import com.example.wlf.gamerecorder.R;import java.util.Date;import java.util.Timer;import java.util.TimerTask;public class SimpleGameonActivity extends AppCompatActivity { private final static int COUNT = 1; private final static int TOTAL_TIME_24 = 24; private TextView textViewTime24; Timer timer; @Override protected void onCreate(Bundle savedInstanceState) {  super.onCreate(savedInstanceState);  setContentView(R.layout.activity_simple_gameon);  textViewTime24=(TextView)findViewById(R.id.textViewTime24);//24秒倒计时  final Button button_start_timer = (Button)findViewById(R.id.button_start_timer);  button_start_timer.setOnClickListener(new View.OnClickListener() {   @Override   public void onClick(View v) {    String str = button_start_timer.getText().toString();//获取按钮字符串    if(str.equals("开始")){ //切换按钮文字     button_start_timer.setText("暂停");     initView();    }    else{     button_start_timer.setText("开始");     timer.cancel();//终止线程    }   }  }); } public void initView(){  //countDown = (TextView) findViewById(R.id.textViewTime24);  timer = new Timer();  /**   * 每一秒发送一次消息给handler更新UI   * schedule(TimerTask task, long delay, long period)   */  timer.schedule(new TimerTask() {   @Override   public void run() {    handler.sendEmptyMessage(COUNT);   }  }, 0, 1000); } private Handler handler = new Handler(){  int num = TOTAL_TIME_24;  public void handleMessage(android.os.Message msg) {   switch (msg.what) {    case COUNT:     textViewTime24.setText(String.valueOf(num));     if(num == 0)      timer.cancel();//0秒结束     num--;     break;    default:     break;   }  }; };}