Question

我最初遵循android developers上的教程，但由于我计划在页面上有两个，我觉得从拾取器中提取值会更优雅一些。我首先在XML中使用了onClick方法;但是，现在，我试图在按下按钮（btn_schedule_adventure）后拉出值。我尝试设置DateView

时收到错误

DatePicker startDatePicker = (DatePicker) findViewById(R.id.picker_start_date);

我下面的代码会抛出错误。我如何能： 1 - 从日期/时间选择器中拉出值（绕过下面的错误） 2 - 保持默认时间/日期

提前致谢。

错误：

05-26 04:27:44.084: E/AndroidRuntime(798): FATAL EXCEPTION: main
05-26 04:27:44.084: E/AndroidRuntime(798): java.lang.ClassCastException: android.widget.Button cannot be cast to android.widget.DatePicker
05-26 04:27:44.084: E/AndroidRuntime(798):  at com.scarr025.zwilio.AdventureSetUp$1.onClick(AdventureSetUp.java:40)
05-26 04:27:44.084: E/AndroidRuntime(798):  at android.view.View.performClick(View.java:4204)
05-26 04:27:44.084: E/AndroidRuntime(798):  at android.view.View$PerformClick.run(View.java:17355)
05-26 04:27:44.084: E/AndroidRuntime(798):  at android.os.Handler.handleCallback(Handler.java:725)
05-26 04:27:44.084: E/AndroidRuntime(798):  at android.os.Handler.dispatchMessage(Handler.java:92)
05-26 04:27:44.084: E/AndroidRuntime(798):  at android.os.Looper.loop(Looper.java:137)
05-26 04:27:44.084: E/AndroidRuntime(798):  at android.app.ActivityThread.main(ActivityThread.java:5041)
05-26 04:27:44.084: E/AndroidRuntime(798):  at java.lang.reflect.Method.invokeNative(Native Method)
05-26 04:27:44.084: E/AndroidRuntime(798):  at java.lang.reflect.Method.invoke(Method.java:511)
05-26 04:27:44.084: E/AndroidRuntime(798):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
05-26 04:27:44.084: E/AndroidRuntime(798):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
05-26 04:27:44.084: E/AndroidRuntime(798):  at dalvik.system.NativeStart.main(Native Method)

方法

public class AdventureSetUp extends Activity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    //Remove title bar
    //this.requestWindowFeature(Window.FEATURE_NO_TITLE);
    Log.d("$$LOGCHECK$$", "In onCreate");

    setContentView(R.layout.activity_adventure_set_up); 

    Button btnScheduleAdventure = (Button) findViewById(R.id.btn_schedule_adventure);
    btnScheduleAdventure.setOnClickListener(new View.OnClickListener() {
                    //perform your action here
        public void onClick(View v) {
            // Get adventure title
            EditText btnScheduleAdventure = (EditText) findViewById(R.id.adventure_title);
            String adventureTitle = btnScheduleAdventure.getText().toString();
            // Get adventure start date
            DatePicker startDatePicker = (DatePicker) findViewById(R.id.picker_start_date);
            int startDay = startDatePicker.getDayOfMonth();
            int startMonth = startDatePicker.getMonth();
            int startYear = startDatePicker.getYear();      

            Log.d("$$LOGCHECK$$", "Clicked Schedule Adventure");
            Log.d("$$LOGCHECK$$", "Title: " + adventureTitle);
            Log.d("$$LOGCHECK$$", "Start Date: " + startMonth + "-" + startDay + "-" + startYear);


            Intent newIntent = new Intent();

        }
    });
}

日期/时间选择器代码（来自教程）

//---------------Date/Time Picker Methods-------------------------------------
// Date Picker
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);
    }

    public void onDateSet(DatePicker view, int year, int month, int day) {
        // Do something with the date chosen by the user
        Log.d("$$LOGCHECK$$", "Date Picked--Year:" + year + " Month: " + month + " Day: " + day);
    }
}

public void showDatePickerDialog(View v) {
    DialogFragment newFragment = new DatePickerFragment();
    newFragment.show(getFragmentManager(), "datePicker");
}

// Time Picker
public static class TimePickerFragment extends DialogFragment
    implements TimePickerDialog.OnTimeSetListener {

    @Override
    public Dialog onCreateDialog(Bundle savedInstanceState) {
    // Use the current time as the default values for the picker
        final Calendar c = Calendar.getInstance();
        int hour = c.get(Calendar.HOUR_OF_DAY);
        int minute = c.get(Calendar.MINUTE);

        // Create a new instance of TimePickerDialog and return it
        return new TimePickerDialog(getActivity(), this, hour, minute,
        DateFormat.is24HourFormat(getActivity()));
    }

    public void onTimeSet(TimePicker view, int hourOfDay, int minute) {
        // Do something with the time chosen by the user
    }
}

public void showTimePickerDialog(View v) {
    DialogFragment newFragment = new TimePickerFragment();
    newFragment.show(getFragmentManager(), "timePicker");
}

XML

<LinearLayout 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"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:orientation="vertical"
tools:context=".AdventureSetUp" >
<EditText
    android:id="@+id/adventure_title"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:hint="@string/hint_adventure_title"
    android:inputType="textEmailAddress" />
<Button 
    android:id="@+id/picker_start_date"         
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content"
    android:text="@string/btn_adventure_start_date" 
    android:onClick="showDatePickerDialog" />
<Button 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content"
    android:text="@string/btn_adventure_start_time" 
    android:onClick="showTimePickerDialog" />


<Button 
    android:id="@+id/picker_end_date"       
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content"
    android:text="@string/btn_adventure_end_date" 
    android:onClick="showDatePickerDialog" />
<Button 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content"
    android:text="@string/btn_adventure_end_time" 
    android:onClick="showTimePickerDialog" />

<Button 
    android:id="@+id/btn_schedule_adventure"        
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content"
    android:text="@string/btn_schedule_adventure" 
    android:onClick="scheduleAdventure" />
</LinearLayout>

Answer 1

您的问题在此明确说明：

05-26 04:27:44.084: E/AndroidRuntime(798): java.lang.ClassCastException: android.widget.Button cannot be cast to android.widget.DatePicker

因为您正在检索此按钮：

<Button 
    android:id="@+id/picker_start_date"       
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content"
    android:text="@string/btn_adventure_end_date" 
    android:onClick="showDatePickerDialog" />

作为DatePicker：

DatePicker startDatePicker = (DatePicker) findViewById(R.id.picker_start_date);

所以改变这个：

DatePicker startDatePicker = (DatePicker) findViewById(R.id.picker_start_date);

由：

Button startDatePicker = (Button) findViewById(R.id.picker_start_date);

Answer 2

这不是拉取价值的正确方法。

当您点击DatePickerDialog中的设置按钮时，会自动调用onDateSet方法。

单击DatePickerDialog中的Set时，您是否可以在Logcat中看到此行。

Date Picked--Year:" + year + " Month: " + month + " Day: " + day

如何以编程方式从Android中的DatePicker / TimePicker Spinners中提取值？

2 个答案: