java如何使用安卓 studio中其他类的方法

Question

我有两门课。java和其他。java。我的日期差异。java看起来像：

public class DateDifference {
    public static void main(String[] args) {
        // Creates two calendars instances
        Calendar cal1 = Calendar.getInstance();
        Calendar cal2 = Calendar.getInstance();

        // Set the date for both of the calendar instance
        cal1.set(2006, Calendar.DECEMBER, 30);
        cal2.set(2007, Calendar.MAY, 3);

        // Get the represented date in milliseconds
        long millis1 = cal1.getTimeInMillis();
        long millis2 = cal2.getTimeInMillis();

        // Calculate difference in milliseconds
        long diff = millis2 - millis1;

        // Calculate difference in seconds
        long diffSeconds = diff / 1000;

        // Calculate difference in minutes
        long diffMinutes = diff / (60 * 1000);

        // Calculate difference in hours
        long diffHours = diff / (60 * 60 * 1000);

        // Calculate difference in days
        long diffDays = diff / (24 * 60 * 60 * 1000);

        System.out.println("In milliseconds: " + diff + " milliseconds.");
        System.out.println("In seconds: " + diffSeconds + " seconds.");
        System.out.println("In minutes: " + diffMinutes + " minutes.");
        System.out.println("In hours: " + diffHours + " hours.");
        System.out.println("In days: " + diffDays + " days.");
    }
}

我怎样才能打印出其他时间的所有差异。java还是其他类

Answer 1

正如你在As中提到的，从另一个类调用函数，对吗？到目前为止，我从你的问题中了解到的是，你可能把activityClass与常规java类混淆了，后者是完全不同的
活动类——把它当作任何应用程序的入门类，在应用程序中，一切都在发生——小部件、列表、片段等。每当你打开任何应用程序，你首先看到的就是你的活动。好吧在activityClass中，你只能做android studio允许你做的事情。好吗
问题是：

Can you methods from other class in android studio?
yes!

class LoginActivity extends AppCompatActivity {

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.login_main);
OtherClass oC = new OtherClass();
oC.method();
  }
}

其他课程

public class OtherClass{

public void method() {
system.out.println("Yes!!");
   }
}

Answer 2

您需要在DateDifference中创建除main之外的方法，并从所需的类中调用它。e、 g:

public class DateDifference {

    /* 
    * If you're coding for Android you don't need the main function.
    * How to run an Android app is a completely different subject
    */

    public long getDifference(Calendar a, Calendar b) {
        long millisA = a.getTimeInMillis();
        long millisB = b.getTimeInMillis();

        return b - a;
    }

}

public class Others {

    // Say you want to display your diff here
    public void displayDiff() {
        DateDifference dateDifference = new DateDifference();

        Calendar a = Calendar.getInstance();
        Calendar b = Calendar.getInstance();

        a.set(2006, Calendar.DECEMBER, 30);
        b.set(2007, Calendar.MAY, 3);

        long diffMillis = dateDifference.getDifference(a, b);
        long diffSeconds = millisToSeconds(diffMillis);
        long diffMinutes = millisToMinutes(diffMillis);
        long diffHours = millisToHours(diffMillis);
        long diffDays = millisToDays(diffMillis);

        /*
        * If you're coding for Android you won't see this output in your app.
        * How to display data on an Android app is a completely different subject
        */
        System.out.println("In milliseconds: " + diffMillis + " milliseconds.");
        System.out.println("In seconds: " + diffSeconds + " seconds.");
        System.out.println("In minutes: " + diffMinutes + " minutes.");
        System.out.println("In hours: " + diffHours + " hours.");
        System.out.println("In days: " + diffDays + " days.");
    }

    private long millisToSeconds(long millis) {
        return millis / 1000;
    }

    private long millisToMinutes(long millis) {
        return diffMillis / (60 * 1000);
    }

    private long millisToHours(long millis) {
        return diffMillis / (60 * 60 * 1000);
    }

    private long millisToDays(long millis) {
        return diffMillis / (24 * 60 * 60 * 1000);
    }

}

Answer 3

如果你想调用其他方法。java的参数，你可以用它的名字和一个“.”来调用它

Others.whatever(millis1);

whatever方法必须是public和static。 如果想从另一个方法调用变量，可以将其公开

public class DateDifference {
        public long millis1;
        public  long millis2;
        public  long diff;
        public  long diffSeconds;
        public  long diffMinutes;
        public  long diffHours;
        public  long diffDays;
    public static void main(String[] args) {
        // Creates two calendars instances
        Calendar cal1 = Calendar.getInstance();
        Calendar cal2 = Calendar.getInstance();

        // Set the date for both of the calendar instance
        cal1.set(2006, Calendar.DECEMBER, 30);
        cal2.set(2007, Calendar.MAY, 3);

        // Get the represented date in milliseconds
        millis1 = cal1.getTimeInMillis();
        millis2 = cal2.getTimeInMillis();

        // Calculate difference in milliseconds
        diff = millis2 - millis1;

        // Calculate difference in seconds
        diffSeconds = diff / 1000;

        // Calculate difference in minutes
        diffMinutes = diff / (60 * 1000);

        // Calculate difference in hours
        diffHours = diff / (60 * 60 * 1000);

        // Calculate difference in days
        diffDays = diff / (24 * 60 * 60 * 1000);

        System.out.println("In milliseconds: " + diff + " milliseconds.");
        System.out.println("In seconds: " + diffSeconds + " seconds.");
        System.out.println("In minutes: " + diffMinutes + " minutes.");
        System.out.println("In hours: " + diffHours + " hours.");
        System.out.println("In days: " + diffDays + " days.");
    }
}

要访问例如mills1，请执行以下操作：

DateDifference.mills1;

Answer 4

如果我没弄错你的问题，你想调用DateDifference中的代码。可以在DateDifference中创建静态函数。java并将所需代码放在那里，然后调用DateDifference。来自所需类的funstionName（）