Question

我使用对话框制作了DatePicker。当我从对话框设置日期时，程序崩溃并说“不幸的是prgram已经停止”。这是我的代码：

package com.example.reminder;

import java.util.Calendar;

import android.app.DatePickerDialog;
import android.app.Dialog;
import android.app.DialogFragment;
import android.os.Bundle;
import android.widget.DatePicker;
import android.widget.EditText;
import android.widget.TabHost;
import android.widget.TextView;


public class DatePickerFragment extends DialogFragment
implements DatePickerDialog.OnDateSetListener {

    public EditText editText;
    DatePicker dpResult;

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);
//return new DatePickerDialog(getActivity(), (EditSessionActivity)getActivity(), year, month, day);

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

public void onDateSet(DatePicker view, int year, int month, int day) {

    editText.setText(String.valueOf(day) + "/"
            + String.valueOf(month + 1) + "/" + String.valueOf(year));
    // set selected date into datepicker also


}
}

我知道问题出在onDateSet方法中。有人可以帮忙吗？

我的LogCat：

06-05 12:19:40.702: E/AndroidRuntime(2876): FATAL EXCEPTION: main
06-05 12:19:40.702: E/AndroidRuntime(2876): java.lang.NullPointerException
06-05 12:19:40.702: E/AndroidRuntime(2876):     at com.example.reminder.DatePickerFragment.onDateSet(DatePickerFragment.java:38)
06-05 12:19:40.702: E/AndroidRuntime(2876):     at android.app.DatePickerDialog.tryNotifyDateSet(DatePickerDialog.java:148)
06-05 12:19:40.702: E/AndroidRuntime(2876):     at android.app.DatePickerDialog.onClick(DatePickerDialog.java:116)
06-05 12:19:40.702: E/AndroidRuntime(2876):     at com.android.internal.app.AlertController$ButtonHandler.handleMessage(AlertController.java:166)
06-05 12:19:40.702: E/AndroidRuntime(2876):     at android.os.Handler.dispatchMessage(Handler.java:99)
06-05 12:19:40.702: E/AndroidRuntime(2876):     at android.os.Looper.loop(Looper.java:137)
06-05 12:19:40.702: E/AndroidRuntime(2876):     at android.app.ActivityThread.main(ActivityThread.java:5039)
06-05 12:19:40.702: E/AndroidRuntime(2876):     at java.lang.reflect.Method.invokeNative(Native Method)
06-05 12:19:40.702: E/AndroidRuntime(2876):     at java.lang.reflect.Method.invoke(Method.java:511)
06-05 12:19:40.702: E/AndroidRuntime(2876):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
06-05 12:19:40.702: E/AndroidRuntime(2876):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
06-05 12:19:40.702: E/AndroidRuntime(2876):     at dalvik.system.NativeStart.main(Native Method)
06-05 12:19:44.152: E/Trace(2899): error opening trace file: No such file or directory (2)

Answer 1

您的editText未初始化，是一个空（null）变量。

editText在哪里可见？

如果您在布局文件中声明了editText，请使用以下代码获取布局中的editText：

editText= (EditText) findViewById(R.id.editText);

我假设布局文件中的EditText名为editText。

Answer 2

您的edittext未初始化。

您将获得空指针异常，因为您没有初始化edittext。

使用以下内容作为参考。在按钮上单击日期选择器弹出。选择日期并单击设置，日期设置为edittext。

示例：

activity_main.xml中

 <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
 android:layout_width="fill_parent"
 android:layout_height="fill_parent" >

<Button
    android:id="@+id/button1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentBottom="true"
    android:layout_centerHorizontal="true"
    android:text="Button" />

<EditText
    android:id="@+id/editText1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentLeft="true"
    android:layout_alignParentRight="true"
    android:layout_alignParentTop="true"
    android:layout_marginTop="55dp"
    android:ems="10" >

    <requestFocus />
</EditText>

pickerdate类

   public class pickerdate extends Activity {

  static EditText mDateDisplay;
    private Button mPickDate;
    private int mYear;
    private int mMonth;
    private int mDay;

    static final int DATE_DIALOG_ID = 0;



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


        mDateDisplay = (EditText) findViewById(R.id.editText1);
        mPickDate = (Button) findViewById(R.id.button1);


        mPickDate.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
               // showDialog(DATE_DIALOG_ID);
                DialogFragment newFragment = new DatePickerFragment();
                newFragment.show(getFragmentManager(), "datePicker");
            }
        });


    }


    public static class DatePickerFragment extends DialogFragment
    implements DatePickerDialog.OnDateSetListener {

        public EditText editText;
        DatePicker dpResult;

    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);
    //return new DatePickerDialog(getActivity(), (EditSessionActivity)getActivity(), year, month, day);

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

    public void onDateSet(DatePicker view, int year, int month, int day) {

        mDateDisplay .setText(String.valueOf(day) + "/"
                + String.valueOf(month + 1) + "/" + String.valueOf(year));
        // set selected date into datepicker also


    }
    }
}

enter image description here

在EditText中设置日期时出错

2 个答案: