Java 使用时钟更新TextView

我一直在尝试创建一个程序，该程序将输出一个工作的数字时钟，使我能够快速访问日期和时间。我有解析时间的代码，但是，我很难更新textview。我有这个：

    `public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    timer = (TextView)findViewById(R.id.timer);

    time = new Time();
    time.setToNow();

    timeString = time.toString();
    changeTime = Parser(timeString);


    time.setToNow();
    timeString = time.toString();
    changeTime = Parser(timeString);

    timer.setText(changeTime);  
    } 
    private String Parser(String time){

    String year = time.substring(0, 4);
    String month = time.substring(4,6);
    String day = time.substring(6, 8);
    String hour = time.substring(9,11);
    String minute = time.substring(11, 13);
    String second = time.substring(13, 15);

    String finalTime = hour + ":" + minute + ":" + second + " " + day + " " + month + " "  + year;
    //String finalTime = second;
    return finalTime;


}`

如何将其放入循环中以不断更新textview

---

感谢您提供的任何帮助。

声明一个处理程序以更新UI线程上的TextView

private Handler mHandler = new Handler() {
 @Override
 public void handleMessage(Message msg) {
    time = new Time();
    time.setToNow();

    timeString = time.toString();
    changeTime = Parser(timeString); 
    timer.setText(changeTime);  
 }
};

启动将更新TextView的TimeTask

int initialDelay = 1000; //first update in miliseconds
int period = 5000;      //nexts updates in miliseconds       

Timer timer = new Timer();
TimerTask task = new TimerTask() {
  public void run() {
      Message msg = new Message();
      mHandler.sendMessage(msg);
  }
};
timer.scheduleAtFixedRate(task, initialDelay, period);

---

你应该使用一个定时器线程。您还可以使用

日历

简化时间和日期转换，并使用

格式

优化字符串创建。此示例将每秒（1000毫秒）更新您的

TextView

：

---

这可以在android中的线程帮助下轻松完成，但由于您希望访问ui，因此线程无法帮助您。您最好选择处理程序或timertask

但是，异步任务也在非ui线程上运行，因此在timertask中创建一个处理程序

Timer t=Timer();

    t.scheduleAtFixedRate(new TimerTask(new Runnable()
        {
    public void run(){
    Handler h=new Handler(getMainLooper());
    h.post(new Runnable(
){public void run(){
//get the time here and set the textview here as here it has access to the main ui
}});
    }
    }
    ), long delay, Long period);

---

很抱歉，错误的代码格式设置……但这对您很有用

使用永无止境的处理程序消息开始更新视图是一种不好的做法（请尝试查看您的进程的CPU级别）。 更好、更优雅的方法是注册一个将触发更新的

BroadcastReceiver

public class Clock extends LinearLayout {

    private Calendar mCalendar;
    private LinearLayout mLayoutTime;
    private TextView mAMPMText;
    private TextView mDateText;
    private TextView mTimeText;
    private View mSendFeedback;
    private boolean mAttached;

    private final Handler mHandler = new Handler();
    SimpleDateFormat dateFormatter = new SimpleDateFormat("EEE, MMM d, yyyy");
    SimpleDateFormat timeFormatter = new SimpleDateFormat("h:mm");

    public Clock(final Context context, int layoutResourceID, int dateResId, int meResId,int amPmResId) {
        super(context);
        LayoutInflater layoutInflater = LayoutInflater.from(context);
        View view = layoutInflater.inflate(layoutResourceID, null);
        addView(view, new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT));
        mAMPMText = (TextView) view.findViewById(amPmResId);
        mTimeText = (TextView) view.findViewById(timeResId);
        mDateText = (TextView) view.findViewById(dateResId);    
    }

    @Override
    protected void onAttachedToWindow() {
        super.onAttachedToWindow();

        if (!mAttached) {
            mAttached = true;
            IntentFilter filter = new IntentFilter();

            filter.addAction(Intent.ACTION_TIME_TICK);
            filter.addAction(Intent.ACTION_TIME_CHANGED);
            filter.addAction(Intent.ACTION_TIMEZONE_CHANGED);

            getContext().registerReceiver(mIntentReceiver, filter, null, mHandler);
        }

        // NOTE: It's safe to do these after registering the receiver since the receiver always runs
        // in the main thread, therefore the receiver can't run before this method returns.

        // The time zone may have changed while the receiver wasn't registered, so update the Time
        mCalendar = Calendar.getInstance();

        // Make sure we update to the current time
        onTimeChanged();
        updateView();
    }

    @Override
    protected void onDetachedFromWindow() {
        super.onDetachedFromWindow();
        if (mAttached) {
            getContext().unregisterReceiver(mIntentReceiver);
            mAttached = false;
        }
    }

    private void updateView(){
        mTimeText.setText(timeFormatter.format(mCalendar.getTime()));
        mDateText.setText(dateFormatter.format(mCalendar.getTime()));
        mAMPMText.setText(mCalendar.get(Calendar.AM_PM) == 0 ? "AM" : "PM");
    }

    private void onTimeChanged() {
        mCalendar.setTime(new Date());

        updateContentDescription(mCalendar);
    }

    private final BroadcastReceiver mIntentReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            if (intent.getAction().equals(Intent.ACTION_TIMEZONE_CHANGED)) {
                String tz = intent.getStringExtra("time-zone");
                mCalendar.setTimeZone(TimeZone.getTimeZone(tz));
            }

            onTimeChanged();

            updateView();
        }
    };

    private void updateContentDescription(Calendar calendar) {
        setContentDescription(calendar.toString());
    }
}

布局（可以做得更好）

您可以使用

线程

、

时间任务

或

处理程序。postdelayed

不断更新文本视图，而不是使用循环。这似乎会使格式化的时间出现，但似乎不会更新。你知道我可能做错了什么吗？@JJJ1106，是的-我修正了我的帖子。您需要在

TimerTask

内创建

Calendar

实例。如果这对你有用，请考虑接受这个答案，因为它很简单。

public class Clock extends LinearLayout {

    private Calendar mCalendar;
    private LinearLayout mLayoutTime;
    private TextView mAMPMText;
    private TextView mDateText;
    private TextView mTimeText;
    private View mSendFeedback;
    private boolean mAttached;

    private final Handler mHandler = new Handler();
    SimpleDateFormat dateFormatter = new SimpleDateFormat("EEE, MMM d, yyyy");
    SimpleDateFormat timeFormatter = new SimpleDateFormat("h:mm");

    public Clock(final Context context, int layoutResourceID, int dateResId, int meResId,int amPmResId) {
        super(context);
        LayoutInflater layoutInflater = LayoutInflater.from(context);
        View view = layoutInflater.inflate(layoutResourceID, null);
        addView(view, new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT));
        mAMPMText = (TextView) view.findViewById(amPmResId);
        mTimeText = (TextView) view.findViewById(timeResId);
        mDateText = (TextView) view.findViewById(dateResId);    
    }

    @Override
    protected void onAttachedToWindow() {
        super.onAttachedToWindow();

        if (!mAttached) {
            mAttached = true;
            IntentFilter filter = new IntentFilter();

            filter.addAction(Intent.ACTION_TIME_TICK);
            filter.addAction(Intent.ACTION_TIME_CHANGED);
            filter.addAction(Intent.ACTION_TIMEZONE_CHANGED);

            getContext().registerReceiver(mIntentReceiver, filter, null, mHandler);
        }

        // NOTE: It's safe to do these after registering the receiver since the receiver always runs
        // in the main thread, therefore the receiver can't run before this method returns.

        // The time zone may have changed while the receiver wasn't registered, so update the Time
        mCalendar = Calendar.getInstance();

        // Make sure we update to the current time
        onTimeChanged();
        updateView();
    }

    @Override
    protected void onDetachedFromWindow() {
        super.onDetachedFromWindow();
        if (mAttached) {
            getContext().unregisterReceiver(mIntentReceiver);
            mAttached = false;
        }
    }

    private void updateView(){
        mTimeText.setText(timeFormatter.format(mCalendar.getTime()));
        mDateText.setText(dateFormatter.format(mCalendar.getTime()));
        mAMPMText.setText(mCalendar.get(Calendar.AM_PM) == 0 ? "AM" : "PM");
    }

    private void onTimeChanged() {
        mCalendar.setTime(new Date());

        updateContentDescription(mCalendar);
    }

    private final BroadcastReceiver mIntentReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            if (intent.getAction().equals(Intent.ACTION_TIMEZONE_CHANGED)) {
                String tz = intent.getStringExtra("time-zone");
                mCalendar.setTimeZone(TimeZone.getTimeZone(tz));
            }

            onTimeChanged();

            updateView();
        }
    };

    private void updateContentDescription(Calendar calendar) {
        setContentDescription(calendar.toString());
    }
}

    <?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="wrap_content"
    android:layout_height="match_parent"
    android:gravity="center_vertical"
    android:orientation="horizontal" >

    <LinearLayout
        android:id="@+id/layout_time"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="horizontal" >

        <TextView
            android:id="@+id/time_txt"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:includeFontPadding="true" />

        <TextView
            android:id="@+id/am_pm_txt"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="AM" />
    </LinearLayout>

    <TextView
        android:id="@+id/date_txt"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

</RelativeLayout>