在執行readContacts()
方法之前contactsList
爲空,換句話說,執行contactsView.setAdapter(adapter)
時,contactsList
爲空,爲什麼此代碼仍然可以正確顯示聯繫人信息?爲什麼我不需要使用Adapter.notifyDataSetChanged()?
public class MainActivity extends AppCompatActivity {
ListView contactsView;
ArrayAdapter<String> adapter;
List<String> contactsList = new ArrayList<String>();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
contactsView = (ListView) findViewById(R.id.contacts_list);
adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, contactsList);
contactsView.setAdapter(adapter);
readContacts();
}
private void readContacts() {
Cursor cursor = null;
try {
cursor = getContentResolver().query(
ContactsContract.CommonDataKinds.Phone.CONTENT_URI,
null, null, null, null);
while (cursor.moveToNext()) {
String displayName = cursor.getString(cursor.getColumnIndex(
ContactsContract.CommonDataKinds.Phone.DISPLAY_NAME
));
String number = cursor.getString(cursor.getColumnIndex(
ContactsContract.CommonDataKinds.Phone.NUMBER
));
contactsList.add(displayName + "\n" + number);
}
} catch (Exception e) {
e.printStackTrace();
} finally {
if (cursor != null) {
cursor.close();
}
}
}
}
,但如果我加入這樣的事情,我要叫notifyDataSetChanged()
:
add.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
contactsList.add("blabla");
adapter.notifyDataSetChanged();
}
});
add
是按鈕。 現在說android會自動調用該方法,爲什麼當刪除adapter.notifyDataSetChanged();
時UI無法刷新?
謝謝!但我有一個新的問題,在上面刷新:) – HungryMilk
@HungryMilk嗨有一個更新的解釋看看,如果它可以幫助接受它作爲答案:) –
抱歉,我忘了!謝謝 : ) – HungryMilk