public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    setContentView(R.layout.main);
    Thread myThread = null;

    Runnable runnable = new CountDownRunner();
    myThread= new Thread(runnable);   
    myThread.start();

}

public void doWork() {
    runOnUiThread(new Runnable() {
        public void run() {
            try{
                TextView txtCurrentTime= (TextView)findViewById(R.id.lbltime);
                    Date dt = new Date();
                    int hours = dt.getHours();
                    int minutes = dt.getMinutes();
                    int seconds = dt.getSeconds();
                    String curTime = hours + ":" + minutes + ":" + seconds;
                    txtCurrentTime.setText(curTime);
            }catch (Exception e) {}
        }
    });
}


class CountDownRunner implements Runnable{
    // @Override
    public void run() {
            while(!Thread.currentThread().isInterrupted()){
                try {
                doWork();
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                        Thread.currentThread().interrupt();
                }catch(Exception e){
                }
            }
    }
}

如果你想在android中使用日期/时间，我建议你使用ThreeTenABP，这是java.time的一个版本。*包(可从android上的API 26开始使用)随Java 8一起发布，可作为Java .util. date和Java .util. calendar的替代品。

LocalDate localDate = LocalDate.now();
DateTimeFormatter formatter = DateTimeFormatter.ofLocalizedDate(FormatStyle.MEDIUM);
String date = localDate.format(formatter);
textView.setText(date);

下面是对我有用的代码。请尝尝这个。这是一个简单的方法，从系统调用中获取时间和日期。

public static String getDatetime() {
    Calendar c = Calendar .getInstance();
    System.out.println("Current time => "+c.getTime());
    SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mms");
    String formattedDate = df.format(c.getTime());
    return formattedDate;
}

实际上，最好使用TextClock小部件。它为您处理所有的复杂性，并将尊重用户的12/24小时的偏好。 http://developer.android.com/reference/android/widget/TextClock.html

简单地复制此代码，并希望这为您工作良好。

Calendar c = Calendar.getInstance();
SimpleDateFormat sdf = new SimpleDateFormat("dd:MMMM:yyyy HH:mm:ss a");
String strDate = sdf.format(c.getTime());

public class XYZ extends Activity {

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //setContentView(R.layout.main);

        Calendar c = Calendar.getInstance();
        System.out.println("Current time => "+c.getTime());

        SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        String formattedDate = df.format(c.getTime());
        // formattedDate have current date/time
        Toast.makeText(this, formattedDate, Toast.LENGTH_SHORT).show();


      // Now we display formattedDate value in TextView
        TextView txtView = new TextView(this);
        txtView.setText("Current Date and Time : "+formattedDate);
        txtView.setGravity(Gravity.CENTER);
        txtView.setTextSize(20);
        setContentView(txtView);
    }

}