# 1。我想显示一个datepicker与当前日期预选(我使用butterknife注入)

  @OnClick(R.id.your_view) public void onClickYourView() {

    final Calendar myCalendar = Calendar.getInstance();
    DatePickerDialog.OnDateSetListener date = new DatePickerDialog.OnDateSetListener() {
      @Override
      public void onDateSet(DatePicker view, int year, int monthOfYear, int dayOfMonth) {
        // TODO Auto-generated method stub
        myCalendar.set(Calendar.YEAR, year);
        myCalendar.set(Calendar.MONTH, monthOfYear);
        myCalendar.set(Calendar.DAY_OF_MONTH, dayOfMonth);
        String myFormat = "dd MMMM yyyy"; // your format
        SimpleDateFormat sdf = new SimpleDateFormat(myFormat, Locale.getDefault());

        your_view.setText(sdf.format(myCalendar.getTime()));
      }

    };
    new DatePickerDialog(mContext, date, myCalendar.get(Calendar.YEAR), myCalendar.get(Calendar.MONTH), myCalendar.get(Calendar.DAY_OF_MONTH)).show();

  }

2. 如果您想预选日期，请将最后一部分替换为

new DatePickerDialog(mContext, date, 1990, 0, 1).show();

然后你可以使用myCalendar变量或直接在视图上的文本来获取它。

import android.app.DatePickerDialog;
import android.content.Context;
import android.view.View;
import android.widget.DatePicker;
import android.widget.TextView;

import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Locale;

public class DatePickerHelper {

private final Calendar calendar = Calendar.getInstance();
private final String dateFormat = "MM/dd/yy";
private TextView textView = null;

public DatePickerHelper(final Context context, TextView textView) {
    this.textView = textView;

    // Setup on click listener if the TextView is not null
    if (textView != null) {
        textView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                getDatePickerDialog(context).show();
            }
        });
    }
}

/**
 * Return a new date picker listener tied to the specified TextView field
 * @return
 */
private DatePickerDialog.OnDateSetListener getOnDateSetListener() {
    return new DatePickerDialog.OnDateSetListener() {
        @Override
        public void onDateSet(DatePicker view, int year, int monthOfYear,
                              int dayOfMonth) {
            calendar.set(Calendar.YEAR, year);
            calendar.set(Calendar.MONTH, monthOfYear);
            calendar.set(Calendar.DAY_OF_MONTH, dayOfMonth);

            SimpleDateFormat sdf = new SimpleDateFormat(dateFormat, Locale.US);
            textView.setText(sdf.format(calendar.getTime()));
        }
    };
}

/**
 * Return new DatePickerDialog for field
 * @param context
 * @return
 */
private DatePickerDialog getDatePickerDialog(Context context) {
    return new DatePickerDialog(context, getOnDateSetListener(), calendar
            .get(Calendar.YEAR), calendar.get(Calendar.MONTH),
            calendar.get(Calendar.DAY_OF_MONTH));
}

}

用法:

  DatePickerHelper assessmentDueDateHelper = new DatePickerHelper(AssessmentsDetailActivity.this,
            (TextView) findViewById(R.id.assessmentDueDateEditText));

还有另一种更好的可重用方式:

创建一个类:

class setDate implements OnFocusChangeListener, OnDateSetListener {   

       private EditText editText;
       private Calendar myCalendar;

       public setDate(EditText editText, Context ctx){
           this.editText = editText;
           this.editText.setOnFocusChangeListener(this);
           myCalendar = Calendar.getInstance();
       }

       @Override
       public void onDateSet(DatePicker view, int year, int monthOfYear, int dayOfMonth)     {
           // this.editText.setText();

            String myFormat = "MMM dd, yyyy"; //In which you need put here
            SimpleDateFormat sdformat = new SimpleDateFormat(myFormat, Locale.US);
            myCalendar.set(Calendar.YEAR, year);
            myCalendar.set(Calendar.MONTH, monthOfYear);
            myCalendar.set(Calendar.DAY_OF_MONTH, dayOfMonth);

            editText.setText(sdformat.format(myCalendar.getTime()));

       }

        @Override
        public void onFocusChange(View v, boolean hasFocus) {
            // TODO Auto-generated method stub
            if(hasFocus){
             new DatePickerDialog(ctx, this, myCalendar
                       .get(Calendar.YEAR), myCalendar.get(Calendar.MONTH),
                       myCalendar.get(Calendar.DAY_OF_MONTH)).show();
            }
        }

    }

然后在onCreate函数下调用这个类:

    EditText editTextFromDate = (EditText) findViewById(R.id.editTextFromDate);
    setDate fromDate = new setDate(editTextFromDate, this);

使用数据绑定:

<EditText
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  android:focusable="false"
  android:onClick="@{() -> viewModel.onDateEditTextClicked()}"
  android:hint="@string/hint_date"
  android:imeOptions="actionDone"
  android:inputType="none"
  android:maxLines="1"
  android:text="@={viewModel.filterDate}" />

(参见focusable, inputType和onClick)

在视图模型:

public void onDateEditTextClicked() {
    // do something
}

这是我怎么做的:类似于选择的答案，但使用一个静态对话框类，所以它更可重用，也使用onFocusChange而不是onClick。

editText.setOnFocusChangeListener(new View.OnFocusChangeListener() {
        @Override
        public void onFocusChange(View v, boolean hasFocus) {
            if (hasFocus) {
                DialogFragment datePickerFragment = new DatePickerFragment() {
                    @Override
                    public void onDateSet(DatePicker view, int year, int month, int day) {
                        Log.d(TAG, "onDateSet");
                        Calendar c = Calendar.getInstance();
                        c.set(year, month, day);
                        editText.setText(df.format(c.getTime()));
                        nextField.requestFocus(); //moves the focus to something else after dialog is closed
                    }
                };
                datePickerFragment.show(getActivity().getSupportFragmentManager(), "datePicker");
            }
        }
    });

datepicker对话框。

public static class DatePickerFragment extends DialogFragment implements DatePickerDialog.OnDateSetListener{

    @Override
    public Dialog onCreateDialog(Bundle savedInstanceState) {
        // Use the current date as the default date in the picker
        final Calendar c = Calendar.getInstance();
        int year = c.get(Calendar.YEAR);
        int month = c.get(Calendar.MONTH);
        int day = c.get(Calendar.DAY_OF_MONTH);

        // Create a new instance of DatePickerDialog and return it
        return new DatePickerDialog(getActivity(), this, year, month, day);
    }

    @Override
    public void onDateSet(DatePicker view, int year, int month, int day) {
        //blah
    }
}

下面是一个针对懒人的Kotlin扩展函数:

fun EditText.transformIntoDatePicker(context: Context, format: String, maxDate: Date? = null) {
    isFocusableInTouchMode = false
    isClickable = true
    isFocusable = false

    val myCalendar = Calendar.getInstance()
    val datePickerOnDataSetListener =
        DatePickerDialog.OnDateSetListener { _, year, monthOfYear, dayOfMonth ->
            myCalendar.set(Calendar.YEAR, year)
            myCalendar.set(Calendar.MONTH, monthOfYear)
            myCalendar.set(Calendar.DAY_OF_MONTH, dayOfMonth)
            val sdf = SimpleDateFormat(format, Locale.UK)
            setText(sdf.format(myCalendar.time))
        }

    setOnClickListener {
        DatePickerDialog(
            context, datePickerOnDataSetListener, myCalendar
                .get(Calendar.YEAR), myCalendar.get(Calendar.MONTH),
            myCalendar.get(Calendar.DAY_OF_MONTH)
        ).run {
            maxDate?.time?.also { datePicker.maxDate = it }
            show()
        }
    }
}

用法:

在活动:

editText.transformIntoDatePicker(this, "MM/dd/yyyy")
editText.transformIntoDatePicker(this, "MM/dd/yyyy", Date())

在片段:

editText.transformIntoDatePicker(requireContext(), "MM/dd/yyyy")
editText.transformIntoDatePicker(requireContext(), "MM/dd/yyyy", Date())