Question

我是Android新编码的新手，我编写了这段代码来帮助我评估我的进度，并了解android中的编码。一旦按下开始按钮，计时器就会启动。我认为程序运行正常，每次调试。但是屏幕上没有定时器输出。

请帮助，谢谢 .XML文件

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.android.clockproject.MainActivity">

    <Button
        android:id="@+id/startButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:text="START"
        android:onClick="collectTime"/>

    <TextView
        android:id="@+id/digits_display"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text=""
        android:textSize="50sp"
        android:layout_centerInParent="true"
         />

</RelativeLayout>

.Java文件

package com.example.android.clockproject;

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

import static android.R.attr.button;
import static android.R.attr.onClick;

public class MainActivity extends AppCompatActivity {
    int hours = 0;
    String hoursDisplay = "00";
    int minutes = 0;
    String minutesDisplay = "00";
    int seconds = 0;
    String secondsDisplay = "00";
    int milliSecond = 0;
    String millisecondDisplay = "0";
    String fullTimeDisplay;
    int loop = 7;

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


    /**
     * method collectTime is called when "start" button is pressed
     */

    public void collectTime(View view) {
        while (loop == 7) {
            fullTimeDisplay = hoursDisplay + ":" + minutesDisplay + ":" + secondsDisplay + "." + millisecondDisplay;
            displayMessage(fullTimeDisplay);
            firstDigit();
        }
    }

    /**
     * method is called to increse hours
     *
     * @param hours
     * @return
     */
    private String forthDigit(int hours) {
        hours = hours + 1;
        if (hours == 13) {
            hours = 0;
        }
        if (hours < 10) {
            hoursDisplay = "0" + hours;
        } else {
            hoursDisplay = "" + hours;
        }
        return hoursDisplay;
    }

    /**
     * method is called to increase minutes
     *
     * @param minutes
     * @return
     */
    private String thirdDigit(int minutes) {
        minutes = minutes + 1;
        if (minutes == 60) {
            forthDigit(hours);
            minutes = 0;
        }
        if (minutes < 10) {
            minutesDisplay = "0" + minutes;
        } else {
            minutesDisplay = "" + minutes;
        }
        return minutesDisplay;
    }

    /**
     * method called to increase seconds
     *
     * @return
     */
    private int secondDigit() {
        seconds = seconds + 1;
        if (seconds == 60) {
            thirdDigit(minutes);
            seconds = 0;
        }
        if (seconds < 10) {
            secondsDisplay = "0" + seconds;
        } else {
            secondsDisplay = "" + seconds;
        }
        return seconds;
    }

    /**
     * method called to increase milliseconds
     */
    private void firstDigit() {
        milliSecond = milliSecond + 1;
        if (milliSecond > 9) {
            milliSecond = 0;
            millisecondDisplay = "0";
            secondDigit();
        }
        millisecondDisplay = "" + milliSecond;

    }

    /**
     * This method displays the given fullTimeDisplay "the clock" on the screen.
     */
    public void displayMessage(String fullTimeDisplay) {
        TextView timeDisplayTextView = (TextView) findViewById(R.id.digits_display);
        timeDisplayTextView.setText(fullTimeDisplay);
    }
}

Answer 1

您还没有发布您的xml布局文件，因此很难提供帮助。首先，我尝试使用测试字符串从onCreate（）调用displayMessage（）函数。如果这不起作用，则问题出在您的xml布局中，您需要将其添加到您的问题中，以便我们看到错误。

编辑：

第一次没看到这个。你使用一个阻塞主线程的while循环直到它完成，我不明白为什么它没有设置文本但是任何一种while循环都不是一个好的解决方案，因为你将来尝试运行的其他代码不会工作

我建议将collectTime（）函数更改为：

  public void collectTime(View view) {
        // 30,000 milliseconds is 30 seconds, the 1000 is how many 
        milliseoncds to wait before calling the onTick
        CountDownTimer timer = new CountDownTimer(30000, 1000) {

        public void onTick(long millisUntilFinished) {
            timeDisplayTextView.setText("seconds remaining: " + millisUntilFinished / 1000);
        }

        public void onFinish() {
            timeDisplayTextView.setText("done!");

            // restarts the time to run 30 seconds again
            timer.start();
        }

    }.start();
}

计时器未在屏幕上显示

1 个答案: