CriminalIntent項目開發--后篇

為Criminal Intent應用添加對話框

• 創建DiaologFragment,使用FragmentManager管理對話框，可以靈活的顯示對話框。

要顯示對話框我們需要完成一些步驟：

• 創建DatePickerFragment類；

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();}

• 創建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在屏幕上顯示對話框

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間的數據傳遞

• 前面我們實現了activity間以及fragment的activity間的數據傳遞。現在需要實現同一activity托管的兩個fragment間的數據傳遞

傳遞數據給DataPickerFragment

• 傳遞crime的日期給Fragment,需新建一個newInstance(Date)方法，然后將Date作為argument附件給Fragment。為了返回新的日期給Fragment并更新模型層以及對應的視圖，需要將日期打包為extra并附加到Intent上，然后調用Fragment.onActivityResult(...)的方法，并傳入準備好的Intent參數。

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) { //創建了AlertDialog的實例 //CrimeFragment向DatePickerFragment傳遞日期 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);

返回數據給CrimeFragment

• 設置目標Fragment

private static final int REQUEST_DATE = 0;

• 傳遞數據給目標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);}

• 響應對話框

@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數據庫的使用

• SQLite是類似于MySQL和Postgresql的開源關系型數據庫。不同于其他數據庫的是，SQLite使用單個文件存儲數據，使用SQLite庫讀取數據。
  Android標準庫包含SQLite庫以及配套的一些Java輔助類。

定義schema

• 定義 CrimeTable 內部類(CrimeTable 內部類唯一的用途就是定義描述數據表元素的 String 常量。首先要定義的是數據庫表名（CrimeTable.NAME）)

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

• 定義數據表字段(有了這些數據表元素就可以在Java代碼中安全的引用)

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"; }

創建初始數據庫

• 創建CrimeBaseHelper 類（用于簡單打開SQLiteDatabase）并打開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<>(); }

寫入數據庫

• 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; }

• 插入和更新記錄并刷新

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); }

完成后我們便可以儲存數據在APP中

轉載于:https://www.cnblogs.com/wypboke/p/7670699.html

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