我正在尝试创建一个倒数计时器，其中包括事件的天、小时、分钟和秒？

Question

以下是我在运行应用程序时将倒数计时器显示到文本视图中的代码。但是，当我运行它时，它不会出现。

private TextView countdowndisplay;
private Handler handler;
private Runnable runnable;

countdowndisplay = (TextView) view.findViewById(R.id.countdowntv);

        countDownStart();



 public void countDownStart() {
        handler = new Handler();
        runnable = new Runnable() {
            @RequiresApi(api = Build.VERSION_CODES.N)
            @Override
            public void run() {
                handler.postDelayed(this, 1000);
                try {
                    SimpleDateFormat dateFormat = null;
                    if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.N) {
                        dateFormat = new SimpleDateFormat("yyyy-MM-dd");
                    } else {
                        //Set the optional Date format here for Devices Running ANDROID VERSION BELOW N
                        dateFormat = new SimpleDateFormat("yyyy-MM-dd");
                    }
// Please here set your event date//YYYY-MM-DD
                    Date futureDate = dateFormat.parse("2017-09-23");
                    Date currentDate = new Date();
                    if (!currentDate.after(futureDate)) {
                        long diff = futureDate.getTime()
                                - currentDate.getTime();
                        long days = diff / (24 * 60 * 60 * 1000);
                        diff -= days * (24 * 60 * 60 * 1000);
                        long hours = diff / (60 * 60 * 1000);
                        diff -= hours * (60 * 60 * 1000);
                        long minutes = diff / (60 * 1000);
                        diff -= minutes * (60 * 1000);
                        long seconds = diff / 1000;
                        countdowndisplay.setText("" + String.format("%02d", days, hours, minutes, seconds));

                    }
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        };
        handler.postDelayed(runnable, 1 * 1000);

    }

下面是我想要显示输出的 textView 的 XML。

<TextView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_below="@+id/nextdrifttv"
        android:layout_alignParentRight="true"
        android:layout_alignParentEnd="true"
        android:id="@+id/countdowntv"/>

Answer 1

我会以不同的方式执行此操作，但这可以使用您的代码 - android。

package com.example.coundown.countdownapp;

import android.os.Build;
import android.os.Bundle;
import android.os.Handler;
import android.support.annotation.RequiresApi;
import android.support.v7.app.AppCompatActivity;
import android.widget.TextView;

import java.text.SimpleDateFormat;
import java.util.Date;

public class MainActivity extends AppCompatActivity {
    private TextView countdowndisplay;
    private Handler handler;
    private Runnable runnable;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        countdowndisplay = (TextView) findViewById(R.id.coundowntimer);

        countDownStart();

    }

    public void countDownStart() {
        handler = new Handler();
        runnable = new Runnable() {
            @RequiresApi(api = Build.VERSION_CODES.N)
            @Override
            public void run() {
                handler.postDelayed(this, 1000);
                try {
                    SimpleDateFormat dateFormat = null;
                    if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.N) {
                        dateFormat = new SimpleDateFormat("yyyy-MM-dd");
                    } else {
                        //Set the optional Date format here for Devices Running ANDROID VERSION BELOW N
                        dateFormat = new SimpleDateFormat("yyyy-MM-dd");
                    }
// Please here set your event date//YYYY-MM-DD
                    Date futureDate = dateFormat.parse("2017-09-23");
                    Date currentDate = new Date();
                    if (!currentDate.after(futureDate)) {
                        long diff = futureDate.getTime() - currentDate.getTime();
                        long days = diff / (24 * 60 * 60 * 1000);
                        diff -= days * (24 * 60 * 60 * 1000);
                        long hours = diff / (60 * 60 * 1000);
                        diff -= hours * (60 * 60 * 1000);
                        long minutes = diff / (60 * 1000);
                        diff -= minutes * (60 * 1000);
                        long seconds = diff / 1000;
                        if (countdowndisplay != null)
                            countdowndisplay.setText(String.valueOf(days) + " days \n" + String.valueOf(hours) + " hours \n " + String.valueOf(minutes) + " minutes \n" + String.valueOf(seconds)+ " seconds");

                    }
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        };
        handler.postDelayed(runnable, 1 * 1000);

    }


}

Answer 2

试试这个。您的问题是从可运行更新 UI。

public class MainActivity extends AppCompatActivity {
     TextView countdowndisplay;
    int count=0;
    Handler handler = new Handler();
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);
        countdowndisplay = (TextView) findViewById(R.id.mainText);
        countdowndisplay.setText("really");
        countDownStart();

    }
    void countDownStart(){
        //Post handler after 1 second.
        handler.postDelayed(runnable, 1000);
    }


    Runnable runnable = new Runnable() {
        @Override
        public void run() {
            count++;
            handler.postDelayed(runnable, 1000);
            ///**Update your UI from here**///
            countdowndisplay.setText(count+" Second");
        }
    };
}