Android Programming 3rd Edition Chap 12 Challenge

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Android编程权威指南 第3版 第12章 挑战练习。

挑战练习1 更多对话框

和 DatePickerFragment 几乎完全一样。

挑战练习2 实现响应式 DialogFragment

第一、二步就按提示完成。

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// dialog_date.xml
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_gravity="center"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content">
    <DatePicker
        android:id="@+id/dialog_date_picker"
        android:calendarViewShown="false"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content">
    </DatePicker>

    <Button
        android:id="@+id/date_ok_button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/button_ok"
        android:layout_gravity="center_horizontal|bottom"/>

</FrameLayout>
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// DatePickerFragment.java
public class DatePickerFragment extends DialogFragment {
    public static final String ARG_DATE = "date";
    public static final String EXTRA_DATE = "com.bignerdranch.android.criminalintent.date";
    private static final String TAG = "DatePickerFragment";

    private DatePicker mDatePicker;
    private Button mOKButton;
    private Date mDate;

    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        // 获取 CrimeFragment 传给 DatePickerActivity 的 date 数据
        mDate = (Date) getActivity().getIntent().getSerializableExtra(EXTRA_DATE);
        Log.d(TAG, "onCreate:" + mDate.toString());
    }

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {

        Log.d(TAG, "onCreateView:" + mDate.toString());
        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);
        int hour = calendar.get(Calendar.HOUR_OF_DAY);
        int minute = calendar.get(Calendar.MINUTE);
        int second = calendar.get(Calendar.SECOND);

        View v = inflater.inflate(R.layout.dialog_date, container, false);

        mDatePicker = v.findViewById(R.id.dialog_date_picker);
        mDatePicker.init(year, month, day, null);
        mOKButton = v.findViewById(R.id.date_ok_button);
        mOKButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                int year = mDatePicker.getYear();
                int month = mDatePicker.getMonth();
                int day = mDatePicker.getDayOfMonth();
                Date date = new GregorianCalendar(year, month, day, hour, minute, second).getTime();
                sendResult(Activity.RESULT_OK, date);
            }
        });

        return v;
    }

    // 给 CrimeFragment 返回用户修改的 date 数据
    private void sendResult(int resultCode, Date date){
        Intent intent = new Intent();
        intent.putExtra(EXTRA_DATE, date);
        getActivity().setResult(resultCode, intent);
    }
}
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// DatePickerActivity.java
public class DatePickerActivity extends SingleFragmentActivity{
    private static final String EXTRA_DATE= "com.bignerdranch.android.criminalintent.date";

    @Override
    protected Fragment createFragment() {
        return new DatePickerFragment();
    }
    // 用于 CrimeFragment 调用，传递 date 数据给 DatePickerFragment
    public static Intent newIntent(Context packageContext, Date date){
        Intent intent = new Intent(packageContext, DatePickerActivity.class);
        intent.putExtra(EXTRA_DATE, date);
        return intent;
    }
}
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// CrimeFragment.java
mDateButton.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
        // 修改启动方式
        Intent intent = DatePickerActivity.newIntent(getActivity(), mCrime.getDate());
        startActivityForResult(intent, REQUEST_DATE);
    }
});

...

// onActivityResult 无需修改
@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);
        updateDate();
    }
}

第三步 涉及 第17章

按17章的步骤修改代码，不考虑新建Crime和数据库部分，可使 CrimeList 和 Crime明细 在平板上显示在屏幕两侧。

但是第二步把 DatePicker 托管到 Activity 了，现在启动DatePicker 都是打开一个 Activity 充满屏幕，所以改成判断设备是手机还是平板，决定启动 DatePickerFragment 的方式：

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// CrimeFragment.java
mDateButton.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
        // 如果是手机启动Activity, 若是平板启动对话框 （参考第17章
        if(getActivity().findViewById(R.id.detail_fragment_container) == null){
            Intent intent = DatePickerActivity.newIntent(getActivity(), mCrime.getDate());
            startActivityForResult(intent, REQUEST_DATE);
        }else {
            FragmentManager manager = getFragmentManager();
            DatePickerFragment dialog = DatePickerFragment.newInstance(mCrime.getDate());
            dialog.setTargetFragment(CrimeFragment.this, REQUEST_DATE);
            dialog.show(manager, DIALOG_DATE);
        }
    }
});

现在在平板上就会显示对话框了，但是按 DatePicker 的OK按钮后，CrimeFragment 的日期却不更新。

通过 Logcat 发现，sendResult() 里发送的就是原来的date，怎么回事呢？

之前自己为了方便，实现第二步的时候，用新建 Activity 的方式启动 DatePicker 这个页面，我直接把 onCreateDialog() 里的代码 copy 到了 onCreateView() 里，只改动了 这里：

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// DatePickerFragment.java -- onCreateView()
mDatePicker = v.findViewById(R.id.dialog_date_picker);
mDatePicker.init(year, month, day, null);
mOKButton = v.findViewById(R.id.date_ok_button);
mOKButton.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
        int year = mDatePicker.getYear();
        int month = mDatePicker.getMonth();
        int day = mDatePicker.getDayOfMonth();
        Date date = new GregorianCalendar(year, month, day, hour, minute, second).getTime();
        sendResult(Activity.RESULT_OK, date);
    }
});

而在onCreateDialog里的是：

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// DatePickerFragment.java -- onCreateDialog()
mDatePicker = v.findViewById(R.id.dialog_date_picker);
mDatePicker.init(year, month, day, null);
return new AlertDialog.Builder(getActivity())
        .setView(v)
        .setTitle(R.string.time_picker_title)
        .setPositiveButton(android.R.string.ok, new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                int year = mDatePicker.getYear();
                int month = mDatePicker.getMonth();
                int day = mDatePicker.getDayOfMonth();
                Date date = new GregorianCalendar(year, month, day, mHour, mMinute, mSecond).getTime();
                sendResult(Activity.RESULT_OK, date);
            }
        })
        .create();

通过在生命周期函数里打 log 发现如下生命周期调用顺序：

平板

平板

手机

手机

onCreateView() 在两种方式启动时都会调用，而手机启动 Activity时不会调用 onCreateDialog() 方法。

所以在平板上没返回修改后的 date 应该是mDatePicker init了两次导致的，所以在 onCreateView() 里做一个判断，如果 mDatePicker不为空的话，再对其进行 findViewById 和 init：

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// DatePickerFragment.java
public class DatePickerFragment extends DialogFragment {
    public static final String ARG_DATE = "date";
    public static final String EXTRA_DATE = "com.bignerdranch.android.criminalintent.date";
    public static final String TAG = "DatePickerFragment";

    private DatePicker mDatePicker;
    private Button mOKButton;
    private Date mDate;
    private int mYear;
    private int mMonth;
    private int mDay;
    private int mHour;
    private int mMinute;
    private int mSecond;

    // 新建对话框 Fragment 时用 arguments 传递信息
    public static DatePickerFragment newInstance(Date date){
        Bundle args = new Bundle();
        args.putSerializable(DatePickerFragment.ARG_DATE, date);

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

    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        Log.d(TAG, "onCreate called");
        // Activity 方式启动时获取 date 信息
        Date date = (Date) getActivity().getIntent().getSerializableExtra(EXTRA_DATE);
        if(date != null){
            mDate = date;
            Log.d(TAG, "intent:" + mDate);
        }
        // 对话框方式启动时获取 date 信息
        if(getArguments() != null){
            mDate = (Date) getArguments().getSerializable(DatePickerFragment.ARG_DATE);
            Log.d(TAG, "arguments:" + mDate.toString());
        }

        Calendar calendar = Calendar.getInstance();
        calendar.setTime(mDate);
        mYear = calendar.get(Calendar.YEAR);
        mMonth = calendar.get(Calendar.MONTH);
        mDay = calendar.get(Calendar.DAY_OF_MONTH);
        mHour = calendar.get(Calendar.HOUR_OF_DAY);
        mMinute = calendar.get(Calendar.MINUTE);
        mSecond = calendar.get(Calendar.SECOND);

    }

    // 启动 Activity 时不会调用该方法
    @NonNull
    @Override
    public Dialog onCreateDialog(@Nullable Bundle savedInstanceState) {
        Log.d(TAG, "onCreateDialog");

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

        // 对话框方式不显示多余的 OK 按钮
        mOKButton = v.findViewById(R.id.date_ok_button);
        mOKButton.setVisibility(View.INVISIBLE);

        mDatePicker = v.findViewById(R.id.dialog_date_picker);
        mDatePicker.init(mYear, mMonth, mDay, null);
        return new AlertDialog.Builder(getActivity())
                .setView(v)
                .setTitle(R.string.time_picker_title)
                .setPositiveButton(android.R.string.ok, new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        int year = mDatePicker.getYear();
                        int month = mDatePicker.getMonth();
                        int day = mDatePicker.getDayOfMonth();
                        Date date = new GregorianCalendar(year, month, day, mHour, mMinute, mSecond).getTime();
                        sendResult(Activity.RESULT_OK, date);
                    }
                })
                .create();
    }

    // 创建 Activity 时调用
    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        Log.d(TAG, "onCreateView called");

        View v = inflater.inflate(R.layout.dialog_date, container, false);

        // 避免因重新 init 而使在平板上不能返回修改后的 date 给 CrimeFragment
        if(mDatePicker == null){
            mDatePicker = v.findViewById(R.id.dialog_date_picker);
            mDatePicker.init(mYear, mMonth, mDay, null);
        }
        mOKButton = v.findViewById(R.id.date_ok_button);
        mOKButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                int year = mDatePicker.getYear();
                int month = mDatePicker.getMonth();
                int day = mDatePicker.getDayOfMonth();
                Date date = new GregorianCalendar(year, month, day, mHour, mMinute, mSecond).getTime();
                sendResult(Activity.RESULT_OK, date);
                getActivity().finish();// 按确定后直接返回上一界面--CrimeFragment
            }
        });

        return v;
    }

    // 返回date给CrimeFragment，要判断两种方式
    private void sendResult(int resultCode, Date date){
        Intent intent = new Intent();
        intent.putExtra(EXTRA_DATE, date);
        Log.d(CrimeFragment.TAG, "sendDate:"+ date.toString());
        if(getTargetFragment() == null){
            getActivity().setResult(resultCode, intent);
        }else{
            getTargetFragment().onActivityResult(getTargetRequestCode(), resultCode, intent);
        }
    }
}

最终效果：

平板设备显示对话框

平板设备显示对话框

手机设备显示全屏 Activity

手机设备显示全屏 Activity