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 {
       @Override
        public 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() {
                          @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).getTime();
                              sendResult(Activity.RESULT_OK,date);
                          }
                      })
              .create();
  }
   
  

• 借助FragmentManager在屏幕上顯示對話框

  mDateButton.setOnClickListener(new View.OnClickListener(){
          @Override
          public 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，然後將Date作為argument附件給Fragment。為了返回新的日期給Fragment並更新模型層以及對應的視圖，需要將日期打包為extra並附加到Intent上，然後調用Fragment.onActivityResult(...)的方法，並傳入準備好的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是類似於MySQL和Postgresql的開源關系型數據庫。不同於其他數據庫的是，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（用於簡單打開SQLiteDatabase）並打開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);
    }
    @Override
    public void onCreate(SQLiteDatabase db) {
    }
    @Override
    public 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;
}

• 插入和更新記錄並刷新

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);
}    

完成後我們便可以儲存數據在APP中

CriminalIntent項目開發--後篇