如何通过活动刷新片段的内容？

Question

我目前已经实现了SliderMenu和其定制适配器： http://www.androidhive.info/2013/11/android-sliding-menu-using-navigation-drawer/

不过，我已经修改了HomeFragment有几个按钮，其中一个创建一个自定义对话框。一旦出现对话框，用户键入Project类的标题和描述，然后将其保存到HomeFragment中的ArrayList中。此ArrayList中的对象使用此输入数据进行更新，但我的HomeFragment不显示输入数据。目前我正在尝试使用getFragmentManager（）... Transition ... replace..commit例程，并尝试了一些其他不成功的方法，它给了我一个NullPointerException。我对Android开发相当陌生，但我想找出一种方法将这些数据传递给我的MainActivity，然后显示一个新的HomeFragment视图，除了显示的输入新数据。

这里是在MainActivity：

//package and imports...etc. 


public class MainActivity extends Activity { 
    private DrawerLayout mDrawerLayout; 
    private ListView mDrawerList; 
    private ActionBarDrawerToggle mDrawerToggle; 
    private CharSequence mDrawerTitle; 
    private CharSequence mTitle; 
    private String[] navMenuTitles; 
    private TypedArray navMenuIcons; 
    private ArrayList<NavDrawerItem> navDrawerItems; 
    private NavDrawerListAdapter adapter; 

@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main); 

    mTitle=mDrawerTitle=getTitle(); 
    //load drawer menu items 
    navMenuTitles=getResources().getStringArray(R.array.nav_drawer_items); 
    //nav drawer icons from res 
    navMenuIcons=getResources().obtainTypedArray(R.array.nav_drawer_icons); 

    mDrawerLayout=(DrawerLayout) findViewById(R.id.drawer_layout); 
    mDrawerList=(ListView) findViewById(R.id.list_slidermenu); 

    navDrawerItems=new ArrayList<NavDrawerItem>(); 

    //adding nav drawer items to array 
    navDrawerItems.add(new NavDrawerItem(navMenuTitles[0], navMenuIcons.getResourceId(0, -1))); 
    navDrawerItems.add(new NavDrawerItem(navMenuTitles[1], navMenuIcons.getResourceId(1, -1))); 
    navDrawerItems.add(new NavDrawerItem(navMenuTitles[2], navMenuIcons.getResourceId(2, -1))); 
    navDrawerItems.add(new NavDrawerItem(navMenuTitles[3], navMenuIcons.getResourceId(3, -1))); 
    navDrawerItems.add(new NavDrawerItem(navMenuTitles[4], navMenuIcons.getResourceId(4, -1))); 
    navDrawerItems.add(new NavDrawerItem(navMenuTitles[5], navMenuIcons.getResourceId(5, -1))); 

    //RECYCLE 
    navMenuIcons.recycle(); 
    //set the nav drawerlist adapter 
    adapter=new NavDrawerListAdapter(getApplicationContext(), navDrawerItems); 
    mDrawerList.setAdapter(adapter); 
    //enable action bar app 
    getActionBar().setDisplayHomeAsUpEnabled(true); 
    getActionBar().setHomeButtonEnabled(true); 

    mDrawerToggle=new ActionBarDrawerToggle(this, mDrawerLayout, 
      R.drawable.ic_drawer,//nav menu toggle icon 
      R.string.app_name,//nav drawer open - desc. for access 
      R.string.app_name//nav drawer close - desc. for access  
    ){ 
     public void onDrawerClosed(View view){ 
      getActionBar().setTitle(mTitle); 
      invalidateOptionsMenu(); 
     } 
     public void onDrawerOpened(View drawerView){ 
      getActionBar().setTitle(mDrawerTitle); 
      invalidateOptionsMenu(); 
     } 
    }; 
    mDrawerLayout.setDrawerListener(mDrawerToggle); 

    if(savedInstanceState==null){ 
     displayView(0); 
    } 

    mDrawerList.setOnItemClickListener(new SlideMenuClickListener()); 

} 


@Override 
public boolean onCreateOptionsMenu(Menu menu) { 
    // Inflate the menu; this adds items to the action bar if it is present. 
    getMenuInflater().inflate(R.menu.main, menu); 

    MenuItem shareItem=(MenuItem) menu.findItem(R.id.action_share); 
    ShareActionProvider mShare = (ShareActionProvider) shareItem.getActionProvider(); 
    Intent shareIntent = new Intent(Intent.ACTION_SEND); 
    shareIntent.setAction(Intent.ACTION_SEND); 
    shareIntent.setType("text/plain"); 
    //shareIntent.putExtra(Intent.EXTRA_TEXT, "text to share"); 
    mShare.setShareIntent(shareIntent); 

    return true; 
} 

public boolean onOptionsItemSelected(MenuItem item){ 
    if(mDrawerToggle.onOptionsItemSelected(item)){ 
     return true; 
    } 
    switch(item.getItemId()){ 
    case R.id.action_settings: 
     return true; 

    default: 
     return super.onOptionsItemSelected(item); 
    } 
} 

//called when invalidateOptionsMenu() is triggered 
@Override 
public boolean onPrepareOptionsMenu(Menu menu){ 
    boolean drawerOpen=mDrawerLayout.isDrawerOpen(mDrawerList); 
    menu.findItem(R.id.action_settings).setVisible(!drawerOpen); 
    return super.onPrepareOptionsMenu(menu); 
} 
@Override 
public void setTitle(CharSequence title){ 
    mTitle=title; 
    getActionBar().setTitle(mTitle); 
} 
//using ActionBarDrawerToggle: call during onPostCreate() + onConfigurationChanged() 
@Override 
protected void onPostCreate(Bundle savedInstanceState){ 
    super.onPostCreate(savedInstanceState); 
    mDrawerToggle.syncState(); 
} 
@Override 
public void onConfigurationChanged(Configuration newConfig){ 
    super.onConfigurationChanged(newConfig); 
    mDrawerToggle.onConfigurationChanged(newConfig); 
} 

private class SlideMenuClickListener implements ListView.OnItemClickListener { 
    @Override 
    public void onItemClick(AdapterView<?> parent, View view, int position, long id){ 
     displayView(position); 
    } 
} 

private void displayView(int position){ 
    Fragment fragment = null; 
    switch(position){ 
    case 0: 
     fragment = new HomeFragment(); 
     break; 
    case 1: 
     fragment = new ProjectsFragment(); 
     break; 
    case 2: 
     fragment = new PhotosFragment(); 
     break; 
    case 3: 
     fragment = new CommunityFragment(); 
     break; 
    case 4: 
     fragment = new PagesFragment(); 
     break; 
    case 5: 
     fragment = new InfoFragment(); 
     break; 
    default: 
     break; 
    } 

    if(fragment != null){ 
     FragmentManager fragmentManager = getFragmentManager(); 
     fragmentManager.beginTransaction().replace(R.id.frame_container, fragment).commit(); 

     mDrawerList.setItemChecked(position, true); 
     mDrawerList.setSelection(position); 
     setTitle(navMenuTitles[position]); 
     mDrawerLayout.closeDrawer(mDrawerList);  
    } else{ 
     Log.e("MainActivity", "Error in creating fragment"); 
    } 
} 

}

这里是HomeFragment代码：

//package and imports...etc. 

公共类HomeFragment扩展片段{

public ArrayList<Project> PL; 
public ArrayList<Button> DB; 
public ArrayList<TextView> TL; 
public ArrayList<TextView> DL; 
public Adapter adp; 
public View rootView; 
public HomeFragment(){ 
    PL=new ArrayList<Project>(3); 
    DB=new ArrayList(); 
    TL=new ArrayList(); 
    DL=new ArrayList(); 
} 

@Override 
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 

    rootView = inflater.inflate(R.layout.fragment_home, container, false); 

    final Button newProjectButton = (Button) rootView.findViewById(R.id.new_project_button); 
    DB.add((Button) rootView.findViewById(R.id.first_delete_button)); 
    DB.add((Button) rootView.findViewById(R.id.second_delete_button)); 
    DB.add((Button) rootView.findViewById(R.id.third_delete_button)); 
    DB.add((Button) rootView.findViewById(R.id.fourth_delete_button)); 
    TL.add((TextView) rootView.findViewById(R.id.first_tag_text)); 
    TL.add((TextView) rootView.findViewById(R.id.second_tag_text)); 
    TL.add((TextView) rootView.findViewById(R.id.third_tag_text)); 
    TL.add((TextView) rootView.findViewById(R.id.fourth_tag_text)); 
    DL.add((TextView) rootView.findViewById(R.id.first_desc_text)); 
    DL.add((TextView) rootView.findViewById(R.id.second_desc_text)); 
    DL.add((TextView) rootView.findViewById(R.id.third_desc_text)); 
    DL.add((TextView) rootView.findViewById(R.id.fourth_desc_text)); 

    newProjectButton.setOnClickListener(new View.OnClickListener(){ 
     int i=0; 
     public void onClick(View v){ 
      if(i<4){ 
       PL.add(newProject(rootView)); 
       upText(i, PL.get(i).getTitle(), PL.get(i).getDesc()); 
      } 
      i++; 
     } 
    }); 
    DB.get(0).setOnClickListener(new View.OnClickListener(){ 
     public void onClick(View v){ 
      int i=0; 
      Toast.makeText(getActivity(), "firstDelete: "+PL.get(0).getTitle(), Toast.LENGTH_LONG).show(); 
      /* Do delete stuff here */ 
     } 
    }); 
    DB.get(1).setOnClickListener(new View.OnClickListener(){ 
     public void onClick(View v){ 
      int i=0; 
      Toast.makeText(getActivity(), "secondDelete: "+PL.get(1).getTitle(), Toast.LENGTH_LONG).show(); 
      /* do delete stuff here */ 
     } 
    }); 
    DB.get(2).setOnClickListener(new View.OnClickListener(){ 
     public void onClick(View v){ 
      Toast.makeText(getActivity(), "thirdDelete"+PL.get(2).getTitle(), Toast.LENGTH_LONG).show(); 
      int i=0; 
      /* do delete stuff here */ 
     } 
    }); 
    DB.get(3).setOnClickListener(new View.OnClickListener(){ 
     public void onClick(View v){ 
      Toast.makeText(getActivity(), "fourthDelete: "+PL.get(3).getTitle(), Toast.LENGTH_LONG).show(); 
      int i =0; 
      /* do delete stuff here */ 
     } 
    }); 

    return rootView; 
} 

public void upText(int loc, String title, String desc){ 
    TL.get(loc).setText(PL.get(loc).getTitle()); 
    DL.get(loc).setText(PL.get(loc).getDesc()); 
    Refresh(); 
} 

protected void Refresh() { 
    Fragment f = new HomeFragment(); 
    FragmentManager FM = getFragmentManager(); 
    FM.beginTransaction().replace(this.getId(), f).commit();   
} 

public Project newProject(View view){ 
    //create localized Project 
    final Project P=new Project(); 
    //create DialogBox 
    final Dialog dialog = new Dialog(this.getActivity()); 
    //modify features BEFORE setting content view 
    dialog.requestWindowFeature(Window.FEATURE_NO_TITLE); 

    dialog.setContentView(R.layout.project_dialog); 
    //Create EditBoxes for Dialog 
    final EditText titleEdit=(EditText) dialog.findViewById(R.id.dialog_title_text); 
    final EditText descEdit=(EditText) dialog.findViewById(R.id.dialog_description_text); 
    //define button's text 
    TextView text=(TextView) dialog.findViewById(R.id.dialog_button_create); 
    text.setText("Create"); 
    Button createButton = (Button) dialog.findViewById(R.id.dialog_button_create); 
    // if button is clicked, close the custom dialog 
    createButton.setOnClickListener(new View.OnClickListener() { 
     @Override 
     public void onClick(View v) { 
      P.setTitle(titleEdit.getText().toString()); 
      P.setDesc(descEdit.getText().toString()); 
      Toast.makeText(getActivity(), "Create button: "+P.getTitle(), Toast.LENGTH_LONG).show(); 
      dialog.dismiss(); 
     } 
    }); 

    dialog.show(); 
    return P; 
} 

}

编辑

而不是使用：

 Fragment f = new HomeFragment(); 
    FragmentManager FM = getFragmentManager(); 
    FM.beginTransaction().replace(this.getId(), f).commit(); 

我现在想用：

ListView list = (ListView) getActivity().findViewById(R.id.list_slidermenu); 
    ((BaseAdapter)list.getAdapter()).notifyDataSetChanged(); 

哪个不给我一个NullPointerException异常，但不更新列表。

Answer 1

当您使用FragmentManager创建新事务时，您可以有效地抛弃现有碎片，创建一个新碎片，然后用现有碎片替换新碎片。当然，新的片段类不包含修改的数据，因此显示新的未修改的数据。

看看这一行：

Fragment f = new HomeFragment();

你只是创建一个全新的对象。

您的对话框关闭后，您不应该执行任何片段的交易，而不是只更新现有片段的控制，以反映新的数据。