[英]findViewById returns null. BUT WHY?
I have an Adroid Activity and I want to introduce a custom list view. 我有一个Adroid活动,我想介绍一个自定义列表视图。 This is my onCreate() activity method. 这是我的onCreate()活动方法。
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
LoadListView();
ListView lvw = (ListView)findViewById(android.R.id.list);
lvw.setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
// selected item
String element = ((TextView) view).getText().toString();
// Launching new Activity on selecting single List Item
Intent i = new Intent(getApplicationContext(), AddEntryActivity.class);
// sending data to new activity
i.putExtra("entryToEdit", element);
long idToEdit = Long.parseLong(hEntries.get(position).toString());
i.putExtra("idToEdit", idToEdit);
startActivity(i);
}
});
DbAccess oDb = new DbAccess(this);
}
As you can see LoadListView() method is called to load listview items: 如您所见,调用LoadListView()方法以加载listview项:
private void LoadListView()
{
oDb = new DbAccess(this);
oDb.open();
List<cAttivita> entries = oDb.getAttivita();
CustomListAdapter listAdapter = new CustomListAdapter(MainActivity.this, android.R.layout.simple_list_item_1 , entries);
ListView lvwAttivita = (ListView)findViewById(android.R.id.list);
lvwAttivita.setAdapter(listAdapter);
hEntries = new HashMap();
for(int i = 0; i < entries.size(); i++)
{
hEntries.put(i, entries.get(i).getId());
}
}
CustomListAdapter class: CustomListAdapter类:
public CustomListAdapter(Context context, int textViewResourceId , List<cAttivita> list )
{
super(context, textViewResourceId, list);
mContext = context;
id = textViewResourceId;
items = list ;
}
@Override
public View getView(int position, View v, ViewGroup parent)
{
View mView = v ;
if(mView == null){
LayoutInflater vi = (LayoutInflater)mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
mView = vi.inflate(id, null);
}
TextView text = (TextView) mView.findViewById(R.id.textView);
if(items.get(position) != null )
{
text.setTextColor(Color.WHITE);
text.setText(items.get(position).toString());
text.setBackgroundColor(Color.RED);
int color = Color.argb( 200, 255, 64, 64 );
text.setBackgroundColor( color );
}
return mView;
}
This is activity_main.xml code: 这是activity_main.xml代码:
<TextView android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:id="@+id/textView"
android:textSize="20px"
android:paddingTop="10dip"
android:paddingBottom="10dip"/>
<ListView xmlns:android="schemas.android.com/apk/res/android";
android:id="@android:id/list"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Attività"/>
The problem is in the line: 问题出在行中:
TextView text = (TextView) mView.findViewById(R.id.textView);
Why text returns null? 为什么文本返回null?
Change the following line of code inside your getView() of your CustomAdapter. 在CustomAdapter的getView()中更改以下代码行。
TextView text = (TextView) mView.findViewById(android.R.id.text1);
as you are taking android.R.layout.simple_list_item_1
as layout it should be android.R.id.text1
which is declared internally in Android library. 当您将android.R.layout.simple_list_item_1
用作布局时,它应该是android.R.id.text1
,它在Android库中内部声明。
Change my line of code inside getView() and it works for you. 在getView()中更改我的代码行,它对您有用。
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