CriminalIntent项目开发--后篇

为Criminal Intent应用添加对话框

• 创建DiaologFragment,使用FragmentManager管理对话框，可以灵活的显示对话框。

要显示对话框我们需要完成一些步骤：

• 创建DatePickerFragment类；

public class DatePickerFragment extends DialogFragment {@Overridepublic Dialog onCreateDialog(Bundle saveInstanceState){return new AlertDialog.Builder(getActivity()).setView(v).setTitle(R.string.date_picker_title).setPositiveButton(android.R.string.ok,.create();}

• 创建AlertDialog；

public Dialog onCreateDialog(Bundle saveInstanceState){Date date = (Date) getArguments().getSerializable(ARG_DATE);Calendar calendar = Calendar.getInstance();calendar.setTime(date);int year = calendar.get(Calendar.YEAR);int month = calendar.get(Calendar.MONTH);int day = calendar.get(Calendar.DAY_OF_MONTH);View v = LayoutInflater.from(getActivity()).inflate(R.layout.dialog_date,null);mDatePicker = (DatePicker) v.findViewById(R.id.dialog_date_picker);mDatePicker.init(year,month,day,null);return new AlertDialog.Builder(getActivity()).setView(v).setTitle(R.string.date_picker_title).setPositiveButton(android.R.string.ok,new DialogInterface.OnClickListener() {@Overridepublic 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).getTime();sendResult(Activity.RESULT_OK,date);}}).create();}

• 借助FragmentManager在屏幕上显示对话框

mDateButton.setOnClickListener(new View.OnClickListener(){@Overridepublic void onClick(View v){FragmentManager manager = getFragmentManager();DatePickerFragment dialog =DatePickerFragment.newInstance(mCrime.getDate());dialog.setTargetFragment(CrimeFragment.this,REQUEST_DATE);dialog.show(manager,DIALOG_DATE);}

Fragment间的数据传递

• 前面我们实现了activity间以及fragment的activity间的数据传递。现在需要实现同一activity托管的两个fragment间的数据传递

传递数据给DataPickerFragment

• 传递crime的日期给Fragment,需新建一个newInstance(Date)方法，然后将Date作为argument附件给Fragment。为了返回新的日期给Fragment并更新模型层以及对应的视图，需要将日期打包为extra并附加到Intent上，然后调用Fragment.onActivityResult(...)的方法，并传入准备好的Intent参数。

private static final String ARG_DATE = "date";
private DatePicker mDatePicker;
public static DatePickerFragment newInstance(Date date) {
Bundle args = new Bundle();
args.putSerializable(ARG_DATE, date);DatePickerFragment fragment = new DatePickerFragment();
fragment.setArguments(args);
return fragment;

@Override
public Dialog onCreateDialog(Bundle savedInstanceState) { //创建了AlertDialog的实例
//CrimeFragment向DatePickerFragment传递日期
Date date = (Date) getArguments().getSerializable(ARG_DATE);
Calendar calendar = Calendar.getInstance();
calendar.setTime(date);
int year = calendar.get(Calendar.YEAR);
int month = calendar.get(Calendar.MONTH);
int day = calendar.get(Calendar.DAY_OF_MONTH);

返回数据给CrimeFragment

• 设置目标Fragment

private static final int REQUEST_DATE = 0;

• 传递数据给目标Fragment

public static final String EXTRA_DATE ="com.example.criminalintent.date";
​ private void sendResult(int resultCode, Date date) {
if (getTargetFragment() == null) {
return;
}
Intent intent = new Intent();
intent.putExtra(EXTRA_DATE, date);
getTargetFragment().onActivityResult(getTargetRequestCode(), resultCode, intent);}

• 响应对话框

@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
//super.onActivityResult(requestCode, resultCode, data);
if (resultCode != Activity.RESULT_OK) {
return;
}
if (requestCode == REQUEST_DATE) {
Date date = (Date) data.getSerializableExtra(DatePickerFragment.EXTRA_DATE);
mCrime.setDate(date);
mDateButton.setText(mCrime.getDate().toString());
//updateDate();
}

SQLite数据库的使用

• SQLite是类似于MySQL和Postgresql的开源关系型数据库。不同于其他数据库的是，SQLite使用单个文件存储数据，使用SQLite库读取数据。
  Android标准库包含SQLite库以及配套的一些Java辅助类。

定义schema

• 定义 CrimeTable 内部类(CrimeTable 内部类唯一的用途就是定义描述数据表元素的 String 常量。首先要定义的是数据库表名（CrimeTable.NAME）)

public class CrimeDbSchema {
public static final class CrimeTable {
public static final String NAME = "crimes";
}
}

• 定义数据表字段(有了这些数据表元素就可以在Java代码中安全的引用)

public static final class Cols {
public static final String UUID = "uuid";
public static final String TITLE = "title";
public static final String DATE = "date";
public static final String SOLVED = "solved";
}

创建初始数据库

• 创建CrimeBaseHelper 类（用于简单打开SQLiteDatabase）并打开SQLiteDatabase

public class CrimeBaseHelper extends SQLiteOpenHelper {private static final int VERSION = 1;private static final String DATABASE_NAME = "crimeBase.db";public CrimeBaseHelper(Context context) {super(context, DATABASE_NAME, null, VERSION);}@Overridepublic void onCreate(SQLiteDatabase db) {}@Overridepublic void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {}
}

public class CrimeLab {private static CrimeLab sCrimeLab;private List<Crime> mCrimes;private Context mContext;private SQLiteDatabase mDatabase;...private CrimeLab(Context context) {mContext = context.getApplicationContext();mDatabase = new CrimeBaseHelper(mContext).getWritableDatabase();mCrimes = new ArrayList<>();
}

写入数据库

• 使用ContentValues

private static ContentValues getContentValues(Crime crime) {ContentValues values = new ContentValues();values.put(CrimeTable.Cols.UUID, crime.getId().toString());values.put(CrimeTable.Cols.TITLE, crime.getTitle());values.put(CrimeTable.Cols.DATE, crime.getDate().getTime());values.put(CrimeTable.Cols.SOLVED, crime.isSolved() ? 1 : 0);return values;
}

• 插入和更新记录并刷新

public void addCrime(Crime c) {ContentValues values = getContentValues(c);mDatabase.insert(CrimeTable.NAME, null, values);
}

public void updateCrime(Crime crime) {String uuidString = crime.getId().toString();ContentValues values = getContentValues(crime);mDatabase.update(CrimeTable.NAME, values,CrimeTable.Cols.UUID + " = ?",new String[] { uuidString });
}

@Override
public void onPause() {super.onPause();CrimeLab.get(getActivity()).updateCrime(mCrime);
}    

完成后我们便可以储存数据在APP中