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 类来向后兼容旧的 Android 版本。

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;
}
}

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： “new TimePickerDialog.OnTimeSetListener(){} 类型的方法 onTimeSet(TimePicker, int, int) 必须覆盖超类方法”

谁能告诉我问题是什么？ 我一直在想办法弄明白，这让我感到非常沮丧！

Answer 1

从日志中可以看出，onTimeset 方法没有被调用

嗯，那是因为当您创建 TimePickerDialog 时，您将片段提供为 OnTimeSetListener：

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

换句话说：您没有看到日志语句，因为您的活动中的 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您的MainActivity 的活动转换为您的MainActivity 来轻松解决此问题，或者，如果您更喜欢可重用的东西，可以通过接口回调它。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 对象而不是原始小时/分钟值传递回活动。

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);
    }
}

然后让您的 MainActivity 实现相同的接口，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 cmets 中所述，要启用对多个选择器的支持，您有多种选择。一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...

但是，我更喜欢做的是能够通过为每个选择器提供一个 id 来识别onTimeSet(...) 返回的结果的来源。然后将该 id 包含在结果中，以便我们知道它来自哪里。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，前提是托管活动实现了该接口。所以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，它需要一个 id。该值将设置为片段的参数，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 - 框架会为您完成。

所以让我们更改MainActivity 来实现我们的自定义接口，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。

Answer 2

我让代码使用它。

public class TimePickerFragment extends DialogFragment{
    @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(), (MainActivity)getActivity(), hour, minute, false);
    }
}


public class MainActivity extends FragmentActivity  implements TimePickerDialog.OnTimeSetListener{

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

    }

    @Override
    public void onTimeSet(TimePicker view, int hourOfDay, int minute) {
        // TODO Auto-generated method stub
        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;
    }
}