我正在使用时间选择器让用户输入他所需的时间来执行特定任务,我正在使用支持库中提供的DialogFragment类来向后兼容较旧的Android版本.

以下是我创建TimePickerFragment类的代码,该类在单独的文件中创建,取自：http://developer.android.com/guide/topics/ui/controls/pickers.html：

package com.calls.only;
import java.util.Calendar;
import android.app.Dialog;
import android.app.TimePickerDialog;
import android.os.Bundle;
import android.support.v4.app.DialogFragment;
import android.widget.TimePicker;


public 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, false);
    }

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

主要活动：

package com.calls.only;


import java.util.Calendar;
import java.util.TimeZone;
import android.os.Bundle;
import android.app.AlarmManager;
import android.app.PendingIntent;
import android.content.Context;
import android.content.Intent;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.DialogFragment;
import android.view.Menu;
import android.view.View;
import android.widget.RadioButton;
import android.widget.TextView;

public class MainActivity extends FragmentActivity {

public void InputStartTime(View v) {
    DialogFragment newFragment = new TimePickerFragment();
    newFragment.show(getSupportFragmentManager(), "timePicker");

}

private TimePickerDialog.OnTimeSetListener mTimeSetListener =
        new TimePickerDialog.OnTimeSetListener() {
                    //Overriding onTimeSet causes an error, see below
            public void onTimeSet(TimePicker view, int hourOfDay, int minute) {
               Log.i("TimePicker", "Time picker set!");
            }
        };

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.activity_main, menu);
    return true;
}
}

我没有调用onTimeset方法,因为我可以从日志中看到,如果我尝试覆盖此方法,则会收到错误：
“new TimePickerDialog.OnTimeSetListener(){}类型的onTimeSet(TimePicker,int,int)方法必须覆盖超类方法”

任何人都可以告诉我这是什么问题？
我一直在试图解决这个问题,这让我感到非常沮丧！

解决方法:

the onTimeset method is not being called as I can see from the log

那么,那是因为当你创建TimePickerDialog时,你将片段作为OnTimeSetListener提供：

return new TimePickerDialog(getActivity(), this, hour, minute, false);
                                             ^

换句话说：您没有看到日志语句,因为活动中的mTimeSetListener变量永远不会被设置为您在片段中创建的对话框的侦听器.

您可以通过将片段附加到MainActivity上的活动强制转换,或者如果您更喜欢可重用的东西,通过接口进行回调来轻松解决此问题.在这种情况下,您可以重用OnTimeSetListener接口,但您也可以设置自己的接口,例如,将Calendar对象传递回活动而不是原始小时/分钟值.

在它最基本的形式中,它看起来有点像这样：

public class TimePickerFragment extends DialogFragment {

    @Override public Dialog onCreateDialog(Bundle savedInstanceState) {
        // ... omitted

        if (!(getActivity() instanceof OnTimeSetListener)) throw new IllegalStateException("Activity should implement OnTimeSetListener!");
        OnTimeSetListener timeSetListener =  (OnTimeSetListener) getActivity();

        // Create a new instance of TimePickerDialog and return it
        return new TimePickerDialog(getActivity(), timeSetListener, hour, minute, false);
    }
}

然后让MainActivity实现相同的接口,而不是使用匿名的内部类：

public class MainActivity extends FragmentActivity implements TimePickerDialog.OnTimeSetListener { 

    @Override public void onTimeSet(TimePicker view, int hourOfDay, int minute) {
        Log.i("TimePicker", "Time picker set!");
    }
}

更新：如评论中所述,要启用对多个选择器的支持,您有几种选择.一个是跟踪托管活动中显示的对话框;如果您只需要区分两个选择器,布尔值就可以了,否则枚举将是实现两个以上状态的合适方法.您需要确保在配置更改期间保留此信息,但…

但是,我更喜欢做的是,能够通过向每个选择器提供一个id来识别onTimeSet(…)中返回的结果的来源.然后将该ID包含在结果中,以便我们可以知道它来自何处.我将概述以下总体思路：

public class TimePickerFragment extends DialogFragment implements OnTimeSetListener {

    private int mId;
    private TimePickerDialogListener mListener;

    private static TimePickerFragment newInstance(int id) {
        Bundle args = new Bundle();
        args.putInt("picker_id", id);
        TimePickerFragment fragment = new TimePickerFragment();
        fragment.setArguments(args);
        return fragment;
    }

    @Override public Dialog onCreateDialog(Bundle savedInstanceState) {
        // ... omitted

        mId = getArguments().getInt("picker_id");
        mListener = getActivity() instanceof TimePickerDialogListener ? (TimePickerDialogListener) getActivity() : null;

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

    @Override public void onTimeSet(TimePicker view, int hourOfDay, int minute) {
        if (mListener != null) mListener.onTimeSet(mId, view, hourOfDay, minute);
    }

    public static interface TimePickerDialogListener {
        public void onTimeSet(int id, TimePicker view, int hourOfDay, int minute);
    }

}

我们上面已经改变的是让对话框本身被注册为OnTimeSetListener,然后它将通过TimePickerDialogListener传递数据,前提是托管活动实现了该接口.这就是我们下一步需要做的事情.另外,请注意我添加了一个静态便捷方法来创建一个带有id的新TimePickerFragment.该值将被设置为片段的参数,确保它成为片段状态的一部分,因此您不必自己担心配置更改 – 框架将为您执行此操作.

因此,让我们更改MainActivity以实现我们的自定义界面,并让它使用newInstance方法：

public class MainActivity extends FragmentActivity implements TimePickerFragment.TimePickerDialogListener { 

    private static final int START_TIME_PICKER_ID = 1;
    private static final int END_TIME_PICKER_ID = 2;

    public void InputStartTime(View v) {
        // supply the appropriate id - I'm assuming you'll be adding an InputEndTime method somewhere that will then supply END_TIME_PICKER_ID 
        DialogFragment newFragment = TimePickerFragment.newInstance(START_TIME_PICKER_ID);
        newFragment.show(getSupportFragmentManager(), "timePicker");
    }

    @Override public void onTimeSet(int id, TimePicker view, int hourOfDay, int minute) {
        Log.i("TimePicker", "Time picker set from id " + id + "!");

        // here you can compare the id value to figure out what picker this data came from
    }
}

最后一点：我直接在浏览器中输入了这个,所以要注意任何明显的拼写错误.