如何调用另一个类的非静态方法 [英] How to call non-static method of another class

问题描述

我想知道如何调用一个类的非静态方法的类。

I want to understand how to call a non-static method of one class in another class.

我已经看到类似以下内容：

I have seen something like the following:

Class1 c1 = new Class1();
c1.doSomething();

当Class1的方法中调用另一个类。

when the method Class1 is called in another class.

public class AddA extends AppCompatActivity {
@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_add_a);
        final DatePicker datePicker = (DatePicker) this.findViewById(R.id.DatePicker);
        final TimePicker timePicker = (TimePicker) this.findViewById(R.id.TimePicker);

 Button clear = (Button) this.findViewById(R.id.clear);
        clear.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                subject.setText("");
                message.setText("");
                //DatePicker.setCurrentDateOnView();
                //TimePicker.setCurrentTimeOnView();
                DateTimePicker datePicker = new DateTimePicker();
                datePicker.setCurrentDateOnView(); //null here
            }

        });
//...More code
}

---

public class DateTimePicker extends AddA {
      @Override
        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_add_alerts);

            setCurrentDateOnView();
            setCurrentTimeOnView();
        }

        // display current date
        public void setCurrentDateOnView() { //null here


            final Calendar c = Calendar.getInstance();
            year = c.get(Calendar.YEAR);
            month = c.get(Calendar.MONTH);
            day = c.get(Calendar.DAY_OF_MONTH);

            // set current date into datepicker
            dpResult.init(year, month, day, null);

        }
    ///..More code}

我将不胜AP preciate详细的解释。是的，我已经研究这个概念，但我不能掌握它。谢谢！

I would greatly appreciate a detailed explanation. Yes, I have researched this notion, but I just cannot grasp it. Thanks!

推荐答案

您不需要类继承在所有acheive在你的问题的问题。

You don't need class inheritance at all to acheive the problem in your question.

我能一起抛出此工作的例子，既复位采摘为当前日期。

I was able to throw this working example together that resets both pickers to the current date.

MainActivity

public class MainActivity extends Activity {

    private Button resetButton;
    private DatePicker datePicker;
    private TimePicker timePicker;

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

        resetButton = (Button) findViewById(R.id.btn_reset);
        datePicker = (DatePicker) findViewById(R.id.datePicker);
        timePicker = (TimePicker) findViewById(R.id.timePicker);

        resetButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Calendar c = Calendar.getInstance();

                int year = c.get(Calendar.YEAR);
                int month = c.get(Calendar.MONTH);
                int day = c.get(Calendar.DAY_OF_MONTH);

                datePicker.init(year, month, day, null);

                int hour = c.get(Calendar.HOUR_OF_DAY);
                int minute = c.get(Calendar.MINUTE);

                timePicker.setCurrentHour(hour);
                timePicker.setCurrentMinute(minute);
            }
        });

    }
}

activity_main.xml中

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:layout_width="match_parent"
              android:layout_height="match_parent"
              android:orientation="vertical">

    <Button
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="Reset"
            android:id="@+id/btn_reset"/>
    <DatePicker
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/datePicker" 
            android:layout_gravity="center_horizontal"/>
    <TimePicker
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center_horizontal"
            android:id="@+id/timePicker"/>
</LinearLayout>

---

或者，如果你想方法来设置日期和时间，你可以做到这一点。

---

Or if you want methods to set the date and time, you can do this

resetButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Calendar c = Calendar.getInstance();
                setDate(c);
                setTime(c);
            }
        });


} // end onCreate

private void setDate(Calendar c) {
    int year = c.get(Calendar.YEAR);
    int month = c.get(Calendar.MONTH);
    int day = c.get(Calendar.DAY_OF_MONTH);

    datePicker.init(year, month, day, null);
}

private void setTime(Calendar c) {
    int hour = c.get(Calendar.HOUR_OF_DAY);
    int minute = c.get(Calendar.MINUTE);

    timePicker.setCurrentHour(hour);
    timePicker.setCurrentMinute(minute);
}

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