Android碎片

Question

我正在試驗Android碎片，因此我創建了兩個碎片ListFragment和DetailFragment。問題是，當我點擊ListFragment並調用DetailFragment方法顯示ListFragment中的選定項目時，DetailFragment上未顯示任何結果。這裏是DetailFragment代碼：

private static final String DETAIL_FRAG_TAG = "detail_fragment"; 
private Context appContext = null; 
private TextView lblItemDetail = null; 
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { 
    // inflate the fragment layout 
    View rootView = inflater.inflate(R.layout.fragments_detail_fragment, container, false); 
    lblItemDetail = (TextView) rootView.findViewById(R.id.lbl_itemDetail); 


//at this point the TextView is not null===>see L0g.i 
Log.i(DETAIL_FRAG_TAG, " ---MyDetailFragment---oncreateView()--lblItemDetail =[" + lblItemDetail + "]"); 

    // get the fragment activity context 
    appContext = this.getActivity(); 
    return rootView; 
} 

@Override 
public void onActivityCreated(Bundle savedInstanceState) { 
    // TODO Auto-generated method stub 
    super.onActivityCreated(savedInstanceState); 

} 

/** 
* show the details of the item selected on the listFragment. 
* @param itemDetail - the details of the item selected on ListFragment. 
*/ 
public void showLstItemDetail(String itemDetail) { 

    if (lblItemDetail != null) { 
     // the View to show Text should not be Null. 
     lblItemDetail.setText(itemDetail); 
    } 

    //at this point calling this method shows 
      that the `TextView` is Null yet it's 
     initialized in the 
     oncreate() as a class member variable ---why am i 
    getting Null after the `oncreate` is finished. 
    Log.i(DETAIL_FRAG_TAG, "------showItemDetail---------msg=[" + itemDetail + "] txt=[" + lblItemDetail + "]"); 
} 



//when I create an instance of `MYDetailFragment` and call the method to show the details of item Selected on the `DetailFragment` the `TextView` will be null. Why? 

    MYDetailFragment detailFrag = new MyDetailFragment(); 
    detailFrag.showLstItemDetail("Selected List Item"); 

Answer 1

這兩條線在

片段下面的教程：

MYDetailFragment detailFrag = new MyDetailFragment(); 
detailFrag.showLstItemDetail("Selected List Item"); 

的onCreateView()當時尚未被稱作。這意味着片段rootView永遠不會被創建，並且TextView永遠不會被創建！

只有在您使用片段事務後才能創建視圖，將該片段放入佈局中，然後片段將被附加到活動（onAttach（）），並且在onCreateView（）調用。只有這樣才能設置任何東西。

將參數傳遞給片段的標準最佳做法是使用Bundle。看一個例子代碼：

上的活動：

MYDetailFragment detailFrag = new MYDetailFragment(); 
Bundle b = new Bundle(); 
detailFrag.setArguments(b); 
b.putString("detail", value); 
// then proceed to the fragment transaction 

然後在您的片段：

public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { 
// inflate the fragment layout 
View rootView = inflater.inflate(R.layout.fragments_detail_fragment, container, false); 
lblItemDetail = (TextView) rootView.findViewById(R.id.lbl_itemDetail); 
Bundle b = getArguments(); 
lblItemDetail.setText(b.getString("details")); 

Answer 2

請確認一下如果任何有用的信息Click here