android - 退出对话框 fragment 后如何更新 MainActivity 中的 TextView？

Question

目前，我的主要 Activity 显示任意时间，并按住一个按钮，按下该按钮会弹出一个时间选择器对话框 fragment 。用户在 fragment 中设置新时间并关闭 fragment 后，我希望我的主要 Activity 用用户选择的新时间更新它的 TextView。

我现在的问题是我不知道如何在用户设置时间后更新 Activity 中显示的时间。我试过使用 onResume，但它一直导致应用程序崩溃。退出 fragment 后刷新 Activity 的最佳方式是什么？

我试图实现的流程是用户在 fragment 中设置时间，导致共享首选项更新，然后主 Activity 刷新，用所选时间更新 TextView 。我是不是想错了？

这是我的 TimePickerFragment 类:

package com.example.habitabilitystudy;

import java.util.Calendar;

import android.app.Activity;
import android.app.Dialog;
import android.app.DialogFragment;
import android.app.TimePickerDialog;
import android.content.Context;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.text.format.DateFormat;
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
        Context context = getActivity();
        SharedPreferences sharedPref = context.getSharedPreferences(
                "prediction", Context.MODE_PRIVATE);

        final Calendar c = Calendar.getInstance();
        int defaultHour = c.get(Calendar.HOUR_OF_DAY);
        int defaultMinute = c.get(Calendar.MINUTE);

        int hour = sharedPref.getInt("prediction_hour", defaultHour);
        int minute = sharedPref.getInt("prediction_min", defaultMinute);

        // 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) {
        Context context = getActivity();
        SharedPreferences sharedPref = context.getSharedPreferences(
                "prediction", Context.MODE_PRIVATE);
        SharedPreferences.Editor editorh = sharedPref.edit();
        editorh.putInt("prediction_hour", hourOfDay);
        editorh.commit();
        SharedPreferences.Editor editorm = sharedPref.edit();
        editorm.putInt("prediction_min", minute);
        editorm.commit();
        mCallbacks.TimeUpdated();

    }

    /**
     * Interface
     */
    private FragmentCallbacks mCallbacks;

    public interface FragmentCallbacks {
        void TimeUpdated();
    }

    @Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);
        try {
            mCallbacks = (FragmentCallbacks) activity;
        } catch (ClassCastException e) {
            throw new ClassCastException(
                    "Activity must implement Fragment Two.");
        }
    }

    @Override
    public void onDetach() {
        super.onDetach();
        mCallbacks = null;
    }

}

我的主要 Activity :

package com.example.habitabilitystudy;

import java.util.Calendar;

import android.app.Activity;
import android.app.DialogFragment;
import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.view.View;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends Activity implements
        TimePickerFragment.FragmentCallbacks {

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

        // Use the current time as the default values for the picker
        SharedPreferences sharedPref = this.getSharedPreferences("prediction",
                Context.MODE_PRIVATE);

        final Calendar c = Calendar.getInstance();
        int defaultHour = c.get(Calendar.HOUR_OF_DAY);
        int defaultMinute = c.get(Calendar.MINUTE);

        int hour = sharedPref.getInt("prediction_hour", defaultHour);
        int minute = sharedPref.getInt("prediction_min", defaultMinute);

        String timeString = Integer.toString(hour) + ":"
                + Integer.toString(minute);

        TextView predictionText = (TextView) findViewById(R.id.prediction_time);
        predictionText.setText(timeString);
    }

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

    @Override
    public void TimeUpdated() {
        Toast.makeText(this, "Updated", Toast.LENGTH_SHORT).show();
    }

    public void onClick(View v) {
        switch (v.getId()) {
        case R.id.predictButton:
            startActivity(new Intent(this, MainActivity.class));
            break;
        case R.id.login:
            startActivity(new Intent(this, LoginActivity.class));
            break;
        }
    }
}

我的主要 Activity xml:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <TextView
        android:id="@+id/prediction_time"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:paddingRight="3dip"
        android:background="#5c755e"
        android:gravity="end"
        android:textColor="#3d4935"
        android:textSize="25sp"
        android:textStyle="italic"
        android:text="(c) appsrox.com" /> 


    <Button 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content"
    android:text="@string/adjust_time" 
    android:onClick="showTimePickerDialog" />



</RelativeLayout>

Answer 1

您想在对话框 fragment 中创建一个界面。选择时间后，它将通知 Activity 。如果这给您带来任何问题，请告诉我。

fragment

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
        Context context = getActivity();
        SharedPreferences sharedPref = context.getSharedPreferences(
            "prediction", Context.MODE_PRIVATE);

        final Calendar c = Calendar.getInstance();
        int defaultHour = c.get(Calendar.HOUR_OF_DAY);
        int defaultMinute = c.get(Calendar.MINUTE);

        int hour = sharedPref.getInt("prediction_hour", defaultHour);
        int minute = sharedPref.getInt("prediction_min", defaultMinute);

        // 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) {
        Context context = getActivity();
        SharedPreferences sharedPref = context.getSharedPreferences(
            "prediction", Context.MODE_PRIVATE);
        SharedPreferences.Editor editorh = sharedPref.edit();
        editorh.putInt("prediction_hour", hourOfDay);
        editorh.commit();
        SharedPreferences.Editor editorm = sharedPref.edit();
        editorm.putInt("prediction_min", minute);
        editorm.commit();
        mCallbacks.TimeUpdated(hourOfDay, minute);
    }

    /**
     * Interface
     */
    private FragmentCallbacks mCallbacks;

    public interface FragmentCallbacks {
        void TimeUpdated(int hour, int minute);
    }

    @Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);
        try {
            mCallbacks = (FragmentCallbacks) activity;
        } catch (ClassCastException e) {
            throw new ClassCastException("Activity must implement Fragment Two.");
        }
    }

    @Override
    public void onDetach() {
        super.onDetach();
        mCallbacks = null;
    }

}

主 Activity

public class MainActivity extends Activity implements TimePickerFragment.FragmentCallbacks {

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

        // Use the current time as the default values for the picker
        SharedPreferences sharedPref = this.getSharedPreferences("prediction",
            Context.MODE_PRIVATE);

        final Calendar c = Calendar.getInstance();
        int defaultHour = c.get(Calendar.HOUR_OF_DAY);
        int defaultMinute = c.get(Calendar.MINUTE);

        int hour = sharedPref.getInt("prediction_hour", defaultHour);
        int minute = sharedPref.getInt("prediction_min", defaultMinute);

        String timeString = Integer.toString(hour) + ":"
            + Integer.toString(minute);

        TextView predictionText = (TextView) findViewById(R.id.prediction_time);
        predictionText.setText(timeString);
    }

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

    @Override
    public void TimeUpdated(int hour, int minute) {
        Toast.makeText(this, "Hour: " + hour + " Minute: " + minute, Toast.LENGTH_SHORT).show();
        String timeString = Integer.toString(hour) + ":" + Integer.toString(minute);
        TextView predictionText = (TextView) findViewById(R.id.prediction_time);
        predictionText.setText(timeString);
    }
}