Android Baseadapter zum Füllen von ListView

Question

Ich lerne Android und möchte Listview mit Name & E-Mail des Benutzers zu füllen. Name & E-Mail sind in sqlite Tabelle gespeichert. Ich verwende eine baseadapter, um die Daten an meine Ansicht zu binden.

Hier ist mein Code:

public class Contact { 

    int _id; 
    String _name; 
    String _email; 
    String _phone_number; 
    String _password; 

    public Contact() { 

    } 

    public Contact (int id, String name, String phone_number, String email, String password) { 
     this._id = id; 
     this._name = name; 
     this._email = email; 
     this._phone_number = phone_number; 
     this._password = password; 
    } 

    public Contact (String name, String phone_number, String email, String password){ 
     this._name = name; 
     this._phone_number = phone_number; 
     this._email = email; 
     this._password = password; 
    } 

    // GETTERS AND SETTERS 
} 


public class CustomAdapter extends BaseAdapter { 

    private static LayoutInflater inflater=null; 
    //Context context; 
    ArrayList list; 

    Contact contact; 

    public CustomAdapter (Context context, ArrayList lists) { 
     this.list = lists; 
     inflater = LayoutInflater.from(context); 
    } 

    @Override 
    public int getCount() { 
     int length = list.size(); 
     return length; 
    } 

    @Override 
    public Object getItem(int position) { 
     return list.get(position); 
    } 

    @Override 
    public long getItemId(int position) { 
     return position; 
    } 

    @Override 
    public View getView(int position, View convertView, ViewGroup parent) { 

     if (convertView == null) { 
      convertView = inflater.inflate(R.layout.custom_list_view,null); 
     } 

     contact = null; 
     contact = (Contact) list.get(position); 

     TextView name = (TextView) convertView.findViewById(R.id.user_names); 
     name.setText(contact.get_name()); 

     TextView email = (TextView) convertView.findViewById(R.id.user_emails); 
     email.setText(contact.get_email()); 

     TextView phone = (TextView) convertView.findViewById(R.id.user_phones); 
     phone.setText(contact.get_phone_number()); 

     return convertView; 
    } 
} 

hier Liste size = 4

0 = Manish 
1 = manish.com 
2 = John 
3 = john.com 

aber auf der Linie:

contact = (Contact) list.get(position); 
the cast class exception is thrown 

Die Liste wie folgt angezeigt werden soll:

Manish 
Manish.com 

John 
John.com 

XYZ 
XYZ.com 

Danke für Ihre Hilfe. Log Katze:

FATAL EXCEPTION: main 
                       Process: com.example.manish.userdetail, PID: 21749 
                       java.lang.ClassCastException: java.lang.String cannot be cast to com.example.manish.userdetail.Contact 
                        at com.example.manish.userdetail.CustomAdapter.getView(CustomAdapter.java:67) 
                        at android.widget.AbsListView.obtainView(AbsListView.java:2255) 
                        at android.widget.ListView.makeAndAddView(ListView.java:1790) 
                        at android.widget.ListView.fillDown(ListView.java:691) 
                        at android.widget.ListView.fillFromTop(ListView.java:752) 
                        at android.widget.ListView.layoutChildren(ListView.java:1630) 
                        at android.widget.AbsListView.onLayout(AbsListView.java:2087) 
                        at android.view.View.layout(View.java:14860) 
                        at android.view.ViewGroup.layout(ViewGroup.java:4643) 
                        at android.widget.RelativeLayout.onLayout(RelativeLayout.java:1055) 
                        at android.view.View.layout(View.java:14860) 
                        at android.view.ViewGroup.layout(ViewGroup.java:4643) 
                        at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1671) 
                        at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1525) 
                        at android.widget.LinearLayout.onLayout(LinearLayout.java:1434) 
                        at android.view.View.layout(View.java:14860) 
                        at android.view.ViewGroup.layout(ViewGroup.java:4643) 
                        at android.widget.RelativeLayout.onLayout(RelativeLayout.java:1055) 
                        at android.view.View.layout(View.java:14860) 
                        at android.view.ViewGroup.layout(ViewGroup.java:4643) 
                        at android.support.design.widget.CoordinatorLayout.layoutChild(CoordinatorLayout.java:1037) 
                        at android.support.design.widget.CoordinatorLayout.onLayoutChild(CoordinatorLayout.java:747) 
                        at android.support.design.widget.ViewOffsetBehavior.onLayoutChild(ViewOffsetBehavior.java:42) 
                        at android.support.design.widget.AppBarLayout$ScrollingViewBehavior.onLayoutChild(AppBarLayout.java:1156) 
                        at android.support.design.widget.CoordinatorLayout.onLayout(CoordinatorLayout.java:760) 
                        at android.view.View.layout(View.java:14860) 
                        at android.view.ViewGroup.layout(ViewGroup.java:4643) 
                        at android.support.v4.widget.DrawerLayout.onLayout(DrawerLayout.java:1043) 
                        at android.view.View.layout(View.java:14860) 
                        at android.view.ViewGroup.layout(ViewGroup.java:4643) 
                        at android.widget.FrameLayout.layoutChildren(FrameLayout.java:453) 
                        at android.widget.FrameLayout.onLayout(FrameLayout.java:388) 
                        at android.view.View.layout(View.java:14860) 
                        at android.view.ViewGroup.layout(ViewGroup.java:4643) 
                        at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1671) 
                        at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1525) 
                        at android.widget.LinearLayout.onLayout(LinearLayout.java:1434) 
                        at android.view.View.layout(View.java:14860) 
                        at android.view.ViewGroup.layout(ViewGroup.java:4643) 
                        at android.widget.FrameLayout.layoutChildren(FrameLayout.java:453) 
                        at android.widget.FrameLayout.onLayout(FrameLayout.java:388) 
                        at android.view.View.layout(View.java:14860) 
                        at android.view.ViewGroup.layout(ViewGroup.java:4643) 
                        at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1671) 
                        at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1525) 
                        at android.widget.LinearLayout.onLayout(LinearLayout.java:1434) 
                        at android.view.View.layout(View.java:14860) 
                        at android.view.ViewGroup.layout(ViewGroup.java:4643) 
                        at android.widget.FrameLayout.layoutChildren(FrameLayout.java:453) 
                        at android.widget.FrameLayout.onLayout(FrameLayout.java:388) 
                        at android.view.View.layout(View.java:14860) 
                        at android.view.ViewGroup.layout(ViewGroup.java:4643) 
                        at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:2013) 
                        at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1770) 
                        at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1019) 
                        at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5725) 
                        at android.view.Choreographer$CallbackRecord.run(Choreographer.java:761) 
                        at android.view.Choreographer.doCallbacks(Choreographer.java:574) 
                        at android.view.Choreographer.doFrame(Choreographer.java:544) 
                        at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:747) 
                       at android.os.Handler.handleCallback(Handler.java:73 

Answer 1

Diese, wie Sie Ihre CustomAdapter Klasse sollte wie folgt aussehen

class CustomAdapter extends BaseAdapter { 

    private static LayoutInflater inflater = null; 
    ArrayList<Contact> list; 

    public CustomAdapter(Context context, ArrayList<Contact> lists) { 
     this.list = lists; 
     inflater = LayoutInflater.from(context); 
    } 

    @Override 
    public int getCount() { 
     return list.size(); 
    } 

    @Override 
    public Object getItem(int position) { 
     return list.get(position); 
    } 

    @Override 
    public long getItemId(int position) { 
     return position; 
    } 

    @Override 
    public View getView(int position, View convertView, ViewGroup parent) { 
     ViewHolder holder; 

     if (convertView == null) { 
      convertView = inflater.inflate(R.layout.custom_list_view, parent, false); 
      holder = new ViewHolder(convertView); 
      convertView.setTag(holder); 

     } else { 
      holder = (ViewHolder) convertView.getTag(); 
     } 

     holder.name.setText(list.get(position).get_name()); 
     holder.email.setText(list.get(position).get_email()); 
     holder.phone.setText(list.get(position).get_phone_number()); 

     return convertView; 
    } 

    private static class ViewHolder { 
     TextView name, email, phone; 

     ViewHolder(View covertView) { 
      name = (TextView) covertView.findViewById(R.id.user_names); 
      email = (TextView) covertView.findViewById(R.id.user_emails); 
      phone = (TextView) covertView.findViewById(R.id.user_phones); 
     } 
    } 
} 

Answer 2

hinzufügen statische ViewHolder Klasse, wie es unten gezeigt und ändern Sie Ihre getView() Methode wie folgt:

@Override 
public View getView(int position, View convertView, ViewGroup parent) { 

    if (convertView == null) { 
     convertView = inflater.inflate(R.layout.custom_list_view,null); 

     holder.name = (TextView) convertView.findViewById(R.id.user_names); 
     holder.email = (TextView) convertView.findViewById(R.id.user_emails); 
     holder.phone = (TextView) convertView.findViewById(R.id.user_phones); 
    } 
    else { 
     holder = (ViewHolder) convertView.getTag(); 
    } 

    name.setText(list.get(/*position of name cell*/)); 
    email.setText(list.get(/*position of email cell*/)); 
    phone.setText(list.get(/*position of phone cell*/)); 
} 

private static class ViewHolder { 
    TextView name; 
    TextView email; 
    TextView phone; 
}