Question

作为The Big Nerd Ranch的Android指南示例犯罪意图的一部分，我正在更新一个按钮，其中输入了日期/时间日期/ TimePicker。 Button和Date / TimePicker位于不同的位置片段。我正在使用Intent在它们之间传输数据。它在Pre-Lollipop设备上工作正常，但似乎没有更新按钮 Android 5.0或Lollipop设备上的文字。我错过了什么？

可以在Github看到完整的代码。

CrimeFragment.java

package com.sudhirkhanger.android.criminalintent;

import java.util.Date;
import java.util.UUID;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.text.Editable;
import android.text.TextWatcher;
import android.text.format.DateFormat;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.CompoundButton;
import android.widget.CompoundButton.OnCheckedChangeListener;
import android.widget.EditText;

public class CrimeFragment extends Fragment {
    private Crime mCrime;
    private EditText mTitleField;
    private Button mDateButton;
    private Button mTimeButton;
    private CheckBox mSolvedCheckBox;
    private static final String TAG = "CriminalFragment";
    public static final String EXTRA_CRIME_ID = "com.sudhirkhanger.android.criminalintent.crime_id";
    private static final String DIALOG_DATE = "date";
    private static final String DIALOG_TIME = "time";
    private static final int REQUEST_DATE = 0;
    private static final int REQUEST_TIME = 1;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        UUID crimeId = (UUID) getArguments().getSerializable(EXTRA_CRIME_ID);
        mCrime = CrimeLab.get(getActivity()).getCrime(crimeId);
    }

    private void updateDateAndTime() {
        Date d = mCrime.getDate();
        CharSequence c = DateFormat.format("EEEE, MMM dd, yyyy", d);
        CharSequence t = DateFormat.format("h:mm a", d);
        mDateButton.setText(c);
        mTimeButton.setText(t);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup parent,
            Bundle savedInstanceState) {
        View v = inflater.inflate(R.layout.fragment_crime, parent, false);

        mTitleField = (EditText) v.findViewById(R.id.crime_title);
        mTitleField.setText(mCrime.getTitle());
        mTitleField.addTextChangedListener(new TextWatcher() {
            public void onTextChanged(CharSequence c, int start, int before,
                    int count) {
                mCrime.setTitle(c.toString());
            }

            public void beforeTextChanged(CharSequence c, int start, int count,
                    int after) {
                // This space intentionally left blank
            }

            public void afterTextChanged(Editable c) {
                // This one too
            }
        });

        mDateButton = (Button) v.findViewById(R.id.crime_date);
        mDateButton.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                FragmentManager fm = getActivity().getSupportFragmentManager();
                DatePickerFragment dialog = DatePickerFragment
                        .newInstance(mCrime.getDate());
                dialog.setTargetFragment(CrimeFragment.this, REQUEST_DATE);
                dialog.show(fm, DIALOG_DATE);
            }
        });

        mTimeButton = (Button) v.findViewById(R.id.crime_time);
        mTimeButton.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                FragmentManager fm = getActivity().getSupportFragmentManager();
                TimePickerFragment dialog = TimePickerFragment
                        .newInstance(mCrime.getDate());
                dialog.setTargetFragment(CrimeFragment.this, REQUEST_TIME);
                dialog.show(fm, DIALOG_TIME);
            }
        });

        updateDateAndTime();

        mSolvedCheckBox = (CheckBox) v.findViewById(R.id.crime_solved);
        mSolvedCheckBox.setChecked(mCrime.isSolved());
        mSolvedCheckBox
                .setOnCheckedChangeListener(new OnCheckedChangeListener() {
                    public void onCheckedChanged(CompoundButton buttonView,
                            boolean isChecked) {
                        // Set the crime's solved property
                        mCrime.setSolved(isChecked);
                    }
                });
        return v;
    }

    public static CrimeFragment newInstance(UUID crimeId) {
        Bundle args = new Bundle();
        args.putSerializable(EXTRA_CRIME_ID, crimeId);

        CrimeFragment fragment = new CrimeFragment();
        fragment.setArguments(args);
        return fragment;
    }

    @Override
    public void onActivityResult(int requestCode, int resultCode, Intent data) {
        if (resultCode != Activity.RESULT_OK)
            return;
        if (requestCode == REQUEST_DATE) {
            Date date = (Date) data
                    .getSerializableExtra(DatePickerFragment.EXTRA_DATE);
            mCrime.setDate(date);
            updateDateAndTime();
        } else if (requestCode == REQUEST_TIME) {
            Date date = (Date) data
                    .getSerializableExtra(TimePickerFragment.EXTRA_TIME);
            mCrime.setDate(date);
            updateDateAndTime();
        }
    }
}

DatePickerFragment.java

package com.sudhirkhanger.android.criminalintent;

import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;

import android.app.Activity;
import android.app.AlertDialog;
import android.app.Dialog;
import android.content.DialogInterface;
import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.DialogFragment;
import android.view.View;
import android.widget.DatePicker;
import android.widget.DatePicker.OnDateChangedListener;

public class DatePickerFragment extends DialogFragment {

    public static final String EXTRA_DATE = "com.sudhirkhanger.android.criminalintent.date";
    private Date mDate;

    public static DatePickerFragment newInstance(Date date) {
        Bundle args = new Bundle();
        args.putSerializable(EXTRA_DATE, date);
        DatePickerFragment fragment = new DatePickerFragment();
        fragment.setArguments(args);
        return fragment;
    }

    private void sendResult(int resultCode) {
        if (getTargetFragment() == null)
            return;
        Intent i = new Intent();
        i.putExtra(EXTRA_DATE, mDate);
        getTargetFragment().onActivityResult(getTargetRequestCode(),
                resultCode, i);
    }

    @Override
    public Dialog onCreateDialog(Bundle savedInstanceState) {
        mDate = (Date) getArguments().getSerializable(EXTRA_DATE);
        // Create a Calendar to get the year, month, and day
        final Calendar calendar = Calendar.getInstance();
        // calendar.setTime(mDate);
        int year = calendar.get(Calendar.YEAR);
        int month = calendar.get(Calendar.MONTH);
        int day = calendar.get(Calendar.DAY_OF_MONTH);

        View v = getActivity().getLayoutInflater().inflate(
                R.layout.dialog_date, null);

        DatePicker datePicker = (DatePicker) v
                .findViewById(R.id.dialog_date_datePicker);
        datePicker.init(year, month, day, new OnDateChangedListener() {
            public void onDateChanged(DatePicker view, int year, int month,
                    int day) {
                // Translate year, month, day into a Date object using a
                // calendar
                int hour = calendar.get(Calendar.HOUR_OF_DAY);
                int minute = calendar.get(Calendar.MINUTE);
                mDate = new GregorianCalendar(year, month, day, hour, minute)
                        .getTime();
                // Update argument to preserve selected value on rotation
                getArguments().putSerializable(EXTRA_DATE, mDate);
            }
        });

        return new AlertDialog.Builder(getActivity())
                .setView(v)
                .setTitle(R.string.date_picker_title)
                .setPositiveButton(android.R.string.ok,
                        new DialogInterface.OnClickListener() {
                            public void onClick(DialogInterface dialog,
                                    int which) {
                                sendResult(Activity.RESULT_OK);
                            }
                        }).create();

    }
}

Answer 1

问题不在于Fragments之间的通信，而是由于某种原因，Lollipop中的默认CalendarView DatePicker从不调用OnDateChanged（）方法，因此DatePickerFragment.java中的mDate永远不会被更改; DatePickerFragment向CrimeFragment发送与从CrimeFragment收到的值相同的值，因此它看起来只是两个片段之间的通信不起作用。

Lollipop DatePicker在SpinnerView模式下调用OnDateChanged（），因此CrimeFragment的日期将得到正确更新。不幸的是，Lollipop忽略了dialog_date.xml文件中DatePicker标签中的android：calendarViewShown =“false”指令。强制DatePicker显示为微调器的唯一方法是在DatePicker的xml标记中包含android：datePickerMode =“spinner”指令。您将收到警告，该指令仅在API 21中受支持，但在5.0之前运行Android的设备将被忽略。您必须为5.0之前的设备保留calendarViewShown =“false”指令。

DatePickerDialog似乎已在Android 5.0中得到修复，因此您也可以在DatePickerFragment中使用该资源来使其工作。

Fragments之间通过Intent进行的数据交换适用于5.0之前，但不适用于Android 5.0

1 个答案: