將項目添加到ListView

Question

我想在運行時添加項目到放置在選項卡上的ListView。 但是當我這樣做，我得到一個錯誤。有3個標籤，我不使用ListFragments，因爲我已經在所有選項卡

我的代碼如下

SwipeTabFragment.java

public class SwipeTabFragment extends Fragment { 

    private String tab; 
    private int color; 

    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     Bundle bundle = getArguments(); 
     tab = bundle.getString("tab"); 
     color = bundle.getInt("color"); 
    } 

    @Override 
    public View onCreateView(LayoutInflater inflater, ViewGroup container, 
          Bundle savedInstanceState) { 
     View view = inflater.inflate(R.layout.bookshelf, null); 
     TextView tv = (TextView) view.findViewById(R.id.textView); 
     tv.setText(tab); 
     view.setBackgroundResource(color); 
     return view; 
    } 
} 

TabPagerAdapter.java

public class TabPagerAdapter extends FragmentPagerAdapter { 

    public TabPagerAdapter(FragmentManager fm) { 
     super(fm); 
    } 

    @Override 
    public Fragment getItem(int index) { 
     Bundle bundle = new Bundle(); 
     String tab = ""; 
     int colorResId = 0; 
     SwipeTabFragment swipeTabFragment = new SwipeTabFragment(); 
     switch (index) { 
      case 0: 
       tab = "BookShelf"; 
       bundle.putString("tab",tab); 
       swipeTabFragment.setArguments(bundle); 
       return swipeTabFragment; 


       // break; 
      case 1: 
       tab = "Now Listening"; 
       colorResId = R.color.color2; 
       BookFragment bookFragment = new BookFragment(); 
       return bookFragment; 
       //break; 
      case 2: 
       tab = "Library"; 
       colorResId = R.color.color3; 
       TabLibrary tabLibrary = new TabLibrary(); 
       return tabLibrary; 
       break; 
     } 

     return null; 
    } 

    @Override 
    public int getCount() { 
     return 3; 
    } 
} 

不同的內容

TabLibrary.java

public class TabLibrary extends Fragment { 

    final String LOG_TAG = "myLogs"; 
    ListView lvLibList; 
    ImageButton btAddItem; 
    ArrayList<String> list = new ArrayList<String>(); 
    ArrayAdapter<String> adapter; 

    @Override 
    public View onCreateView(LayoutInflater inflater, ViewGroup parent, Bundle savedInstanceState) { 
     View v = inflater.inflate(R.layout.library, parent, false); 

     ListView lvLibList = (ListView)v.findViewById(R.id.lvLibList); 
     ImageButton btn = (ImageButton)v.findViewById(R.id.btAddItem); 
     adapter = new ArrayAdapter<String>(getActivity(), android.R.layout.simple_list_item_1, list); 
     View.OnClickListener listener = new View.OnClickListener() { 
      @Override 
      public void onClick(View v) { 
       EditText edit = (EditText)v.findViewById(R.id.eAddItem); 
       list.add(edit.getText().toString()); 
       edit.setText(""); 
       adapter.notifyDataSetChanged(); 
      } 
     }; 
     btn.setOnClickListener(listener); 
     lvLibList.setAdapter(adapter); 
     return v; 
    } 

    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
    } 
} 

Answer 1

@Gurusharan S是對的，問題是關於變量的名稱。爲了避免混淆，我建議你的代碼改成這樣：

@Override 
public View onCreateView(LayoutInflater inflater, ViewGroup parent, Bundle savedInstanceState) { 
    View view = inflater.inflate(R.layout.library, parent, false); //Change the name from v to view 

    ListView lvLibList = (ListView)view.findViewById(R.id.lvLibList); 
    ImageButton btn = (ImageButton)view.findViewById(R.id.btAddItem); 
    EditText edit = (EditText)view.findViewById(R.id.eAddItem); //Initialize the EditText outside of the click method 

    adapter = new ArrayAdapter<String>(getActivity(), android.R.layout.simple_list_item_1, list); 

    View.OnClickListener listener = new View.OnClickListener() { 
     @Override 
     public void onClick(View v) { 
      list.add(edit.getText().toString()); 
      edit.setText(""); 
      adapter.notifyDataSetChanged(); 
     } 
    }; 
    btn.setOnClickListener(listener); 
    lvLibList.setAdapter(adapter); 
    return view; 
} 

而在未來我建議，給你的變量更有意義的名稱，有時需要你多一點的編碼，但它是值得的。

Answer 2

發表我的評論作爲答案，因爲我敢肯定這是問題：

變量edit似乎爲空。這是因爲當你打電話給v.findViewById時，你實際上是在被點擊的視圖上調用它，而不是片段的視圖。

所以，你有兩個選擇：

1. 更改片段的視圖的名稱。例如。 View v1 = inflater.inflate(R.layout.library, parent, false);，然後將該行更改爲v1.findViewById
2. 更改onClick參數的名稱。例如。 public void onClick(View v1) {。

希望有所幫助。