退出对话框片段后,如何在MainActivity中更新TextView？

概述当前,我的主要活动显示一个任意时间,并按住一个按钮,当按下该按钮时,将d出一个“时间选择器”对话框片段.用户在“片段”中设置新时间后,关闭片段,我希望我的主要活动使用用户选择的新时间来更新它的TextView.我现在的问题是,在用户设置时间后,我不知道如何更新活动中显示的时间.

当前,我的主要活动显示一个任意时间,并按住一个按钮,当按下该按钮时,将d出一个“时间选择器”对话框片段.用户在“片段”中设置新时间后,关闭片段,我希望我的主要活动使用用户选择的新时间来更新它的TextVIEw.

我现在的问题是,在用户设置时间后,我不知道如何更新活动中显示的时间.我曾尝试过使用onResume进行游戏,但是它一直导致应用崩溃.退出片段后刷新活动的最佳方法是什么？

我试图实现的流程是,用户在片段中设置时间,从而导致共享首选项被更新,然后主活动性刷新,并以所选时间更新文本视图.我是不是在想这个错误？

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;    }}

我的主要活动：

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;        }    }}

我的主要活动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>

解决方法:

您要在对话框片段中创建一个接口.时间选定后,它将通知活动.让我知道这是否给您带来任何问题.

分段

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;    }}

主要活动

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);    }}

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