java - TimePicker onTimeSet 未被调用

Question

我正在使用时间选择器让用户输入他想要的时间来完成特定任务，我正在使用支持库中提供的 DialogFragment 类以实现与旧 Android 版本的向后兼容性。

这是我创建 TimePickerFragment 类的代码，在一个单独的文件中创建，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 Activity :

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;
}
}

从日志中可以看出，没有调用 onTimeset 方法，如果我尝试覆盖此方法，则会收到错误消息:“新 TimePickerDialog.OnTimeSetListener(){} 类型的方法 onTimeSet(TimePicker, int, int) 必须覆盖父类(super class)方法”

谁能告诉我问题出在哪里？我一直在努力解决这个问题，但它让我感到非常沮丧!

Answer 1

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

嗯，那是因为当您创建 TimePickerDialog 时，您将 fragment 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 Activity 中的 mTimeSetListener 变量从未被设置为您在 fragment 中创建的对话的监听器。

您可以通过将 fragment 附加到您的 MainActivity 的 Activity 轻松地解决此问题，或者，如果您更喜欢可重用的东西，请通过接口(interface)让它回调。在这种情况下，您可以重用 OnTimeSetListener 接口(interface)，但您也可以设置自己的接口(interface)，例如，将 Calendar 对象传递回 Activity 而不是原始的小时/分钟值。

在最基本的形式中，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);
    }
}

然后让您的 MainActivity 实现相同的接口(interface)，而不是使用匿名内部类:

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，您有多种选择。一种是跟踪托管 Activity 中显示的对话框；如果您只需要区分两个选择器， boolean 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这条信息......

但是，我更愿意做的是能够通过为每个选择器提供一个 id 来识别 onTimeSet(...) 中返回的结果的来源。该 id 然后包含在结果中，以便我们可以知道它来自哪里。我将在下面概述总体思路:

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);
    }

}

我们在上面所做的更改是将对话框本身注册为 OnTimeSetListener，然后它将通过 TimePickerDialogListener 传递数据，前提是托管 Activity 实现该接口(interface)。这就是我们下一步需要做的。另外请注意，我添加了一个静态便捷方法来创建一个新的 TimePickerFragment，它带有一个 id。该值将设置为 fragment 的参数，确保它成为 fragment 状态的一部分，因此您不必自己担心配置更改 - 框架会为您完成。

所以让我们更改 MainActivity 来实现我们的自定义接口(interface)，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:我是直接在浏览器中输入的，所以请注意任何明显的拼写错误。