一个时间始停APP

package cn.oracle;

import java.text.SimpleDateFormat;
import java.util.Date;
import javafx.application.Application;
import javafx.application.Platform;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.layout.HBox;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;

public class Test_151130_Time extends Application {
 volatile static boolean b = true;
 volatile static boolean a = false;
 static Thread t;
 static int count = 0;

 @Override
 public void start(Stage stage) throws Exception {
  // 声明一个
  VBox box = new VBox(10);
  box.setAlignment(Pos.CENTER);
  // 添加一个文本
  final Label label = new Label("显示时间");
  box.getChildren().add(label);

  HBox hbox = new HBox(10);
  hbox.setAlignment(Pos.CENTER);
  Button btn1 = new Button("启动");
  Button btn2 = new Button("停止");
  hbox.getChildren().addAll(btn1, btn2);

  // 声明一个内部的线程

  t = new Thread() {

     

   @Override
   public void run() {

    SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
    while (true) {
        while (b) {
      String str = sdf.format(new Date());
      System.err.println(str);
      try {
       sleep(1000);
      } catch (InterruptedException e) {

       e.printStackTrace();
      }
      Platform.runLater(new Runnable() {
       @Override
       public void run() {
        label.setText(str);// 设置上面的文本
       }
      }

      );

      }
    }
   }
  };

  // 给btn1添加事件
  btn1.setOnAction(new EventHandler<ActionEvent>() {
   public void handle(ActionEvent event) {
    if (count == 0) {
     t.start();
     count++;
    } else {
     System.out.println("--第" + count + "次重启--");
     count++;
     b = true;
    }

   }
  });
    btn2.setOnAction(new EventHandler<ActionEvent>() {

   @Override
   public void handle(ActionEvent event) {
    System.out.println("--第" + count + "次停止--");
    b = false;
   }

  });
  box.getChildren().add(hbox);

  // 添加用于显示的对象
  Scene scene = new Scene(box, 300, 300);
  stage.setScene(scene);
  stage.show();

 }

 public static void main(String[] args) {
  launch();
 }
}