第22章 Master-Detail 用户界面

22.1.1 修改SingleFragmentActivity

protected int getLayoutResId() {
   return R.layout.activity_fragment;
}

@Override
protected void onCreate(Bundle savedInstanceState) {
   super.onCreate(savedInstanceState);
   setContentView(getLayoutResId());

    ...

22.1.3 使用别名资源

创建默认的别名资源值(res/values/refs.xml)

<resources>
   <item name="activity_masterdetail" type="layout">@layout/activity_fragment</item>
</resources>

用于大屏幕设备的可选资源(res/values-sw600dp/refs.xml)

<resources>
   <item name="activity_masterdetail" type="layout">@layout/activity_twopane</item>
</resources>

再次切换布局(CrimeListActivity.java)

@Override
protected int getLayoutResId() {
   return R.layout.activity_masterdetail;
}

fragment回调接口

添加回调接口(CrimeListFragment.java)

public class CrimeListFragment extends ListFragment {
   private MyCallBacks mCallBacks;

    ...

    public interface MyCallBacks {
       void onCrimeSelected(Crime crime);
    }

    @Override
    public void onAttach(Activity activity) {
       super.onAttach(activity);
       mCallBacks = (MyCallBacks) activity;
    }

    @Override
    public void onDetach() {
       super.onDetach();
       mCallBacks = null;
    }    

实现回调接口(CrimeListActivity.java)

public class CrimeListActivity extends SingleFragmentActivity implements CrimeListFragment.MyCallBacks{

    @Override
public void onCrimeSelected(Crime crime) {
   if (findViewById(R.id.detailFragmentContainer) == null) {
       Intent intent = new Intent(this, CrimePagerActivity.class);
       intent.putExtra(CrimeFragment.EXTRA_CRIME_ID, crime.getId());
       startActivity(intent);
   } else {
       getSupportFragmentManager().
               beginTransaction().
               replace(R.id.detailFragmentContainer, CrimeFragment.newInstance(crime.getId())).
               commit();

        }

    }

}

调用全部回调方法(CrimeListFragment.java)

@Override
public void onListItemClick(ListView l, View v, int position, long id) {
   super.onListItemClick(l, v, position, id);
   Crime crime = (Crime) getListAdapter().getItem(position);
   mCallBacks.onCrimeSelected(crime);
}



@Override
public boolean onOptionsItemSelected(MenuItem item) {
   switch (item.getItemId()) {
       case R.id.menu_item_new_crime:
           addNewCrime();
           return true;
       default:
           return super.onOptionsItemSelected(item);
   }

}

private void addNewCrime() {
   Crime crime = new Crime();
   CrimeLab.getInstance(getActivity()).addCrime(crime);
   ((CrimeAdapter) getListAdapter()).notifyDataSetChanged();
   mCallBacks.onCrimeSelected(crime);
}

CrimeFragment.Callbacks回调接口的实现

CrimeFragment类中定义的接口如下:

public class CrimeFragment extends Fragment {
   private MyCallBacks mCallBacks;

    ...

    public interface MyCallBacks {
       void onCrimeUpdate();
    }

    @Override
    public void onAttach(Activity activity) {
       super.onAttach(activity);
       mCallBacks = (MyCallBacks) activity;

    }

    @Override
    public void onDetach() {
       super.onDetach();
       mCallBacks = null;
    }

新增updateUI()方法 (CrimeListFragment.java)

public void onUpdateUI() {
   ((CrimeAdapter) getListAdapter()).notifyDataSetChanged();
}

刷新显示crime列表(CrimeListActivity.java)

@Override
public void onCrimeUpdate() {
   ((CrimeListFragment) getSupportFragmentManager().findFragmentById(R.id.fragmentContainer)).onUpdateUI();
}

调用onCrimeUpdated(Crime)方法(CrimeFragment.java)

mTitleField.addTextChangedListener(new TextWatcher() {
   @Override
   public void beforeTextChanged(CharSequence charSequence, int i, int i1, int i2) {

   }

   @Override
   public void onTextChanged(CharSequence charSequence, int i, int i1, int i2) {
       mCrime.setTitle(charSequence.toString());
       mCallBacks.onCrimeUpdate();
       getActivity().setTitle(mCrime.getTitle());
   }

   @Override
   public void afterTextChanged(Editable editable) {

   }
});



mSolvedCheckBox = (CheckBox) view.findViewById(R.id.crime_solved);
mSolvedCheckBox.setChecked(mCrime.isSolved());
mSolvedCheckBox.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
   @Override
   public void onCheckedChanged(CompoundButton compoundButton, boolean b) {
       mCrime.setSolved(b);
       mCallBacks.onCrimeUpdate();
   }
});



@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) {
       mCrime.setDate((Date) data.getSerializableExtra(DatePickerFragment.EXTRA_DATE));

       Log.d(TAG, mCrime.getDate().toString());

       mDateButton.setText(mCrime.getDate().toString());
       mCallBacks.onCrimeUpdate();

   }
   if (requestCode == REQUEST_PHOTO) {
       String filename = data.getStringExtra(CrimeCameraFragment.EXTRA_PHOTO_FILENAME);
       if (filename != null) {
           Photo photo = new Photo(filename);
           mCrime.setPhoto(photo);
           mCallBacks.onCrimeUpdate();
           showPhoto();
       }
   }
   if (requestCode == REQUEST_CONTACT) {
       Uri contactUri = data.getData();
       String[] queryFields = new String[]{ContactsContract.Contacts.DISPLAY_NAME};
       Cursor cursor = getActivity().getContentResolver().query(contactUri, queryFields, null, null, null);
       if (cursor.getCount() == 0) {
           cursor.close();
           return;
       }
       cursor.moveToFirst();
       String suspect = cursor.getString(cursor.getColumnIndex(ContactsContract.Contacts.DISPLAY_NAME));
       mCrime.setSuspect(suspect);
       mCallBacks.onCrimeUpdate();
       mSuspectButton.setText(suspect);
       cursor.close();
   }
}

CrimeListActivity现在有了CrimeFragment.Callbacks接口的一个良好实现。然而,如 果在手机设备上运行CriminalIntent应用,它将会崩溃。记住,任何托管CrimeFragment的activity 都必须实现CrimeFragment.Callbacks接口。因此,我们还需要在CrimePagerActivity类中 实现CrimeFragment.Callbacks接口。

对于CrimePagerActivity类,onCrimeUpdated(Crime)方法什么都不用做,因此直接实现 一个空方法即可

CrimeFragment.Callbacks接口的空实现(CrimePagerActivity.java)

public class CrimePagerActivity extends AppCompatActivity implements CrimeFragment.MyCallBacks{

    @Override
    public void onCrimeUpdate() {
        
    }

    ...

}