嗨，在下面的代码我得到空指针异常。在这里我显示所有的朋友列表。但它没有显示朋友列表它给出空指针异常。 任何人都可以帮助我解决这个问题。 ** FriendList **
public class FriendList extends ListActivity
{
private static final int ADD_NEW_FRIEND_ID = Menu.FIRST;
private static final int CREATE_GROUP_ID = Menu.FIRST+1;
private static final int EXIT_APP_ID = Menu.FIRST + 2;
private IAppManager imService = null;
private FriendListAdapter friendAdapter;
public String ownusername = new String();
private class FriendListAdapter extends BaseAdapter
{
class ViewHolder {
TextView text,text1;
ImageView icon;
}
private LayoutInflater mInflater;
private Bitmap mOnlineIcon;
private Bitmap mOfflineIcon;
private FriendInfo[] friends = null;
public FriendListAdapter(Context context) {
super();
mInflater = LayoutInflater.from(context);
mOnlineIcon = BitmapFactory.decodeResource(context.getResources(), R.drawable.greenstar);
mOfflineIcon = BitmapFactory.decodeResource(context.getResources(), R.drawable.redstar);
}
public void setFriendList(FriendInfo[] friends)
{
this.friends = friends;
}
public int getCount() {
return friends.length;
}
public FriendInfo getItem(int position) {
return friends[position];
}
public long getItemId(int position) {
return 0;
}
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder holder;
if (convertView == null)
{
convertView = mInflater.inflate(R.layout.friend_list_screen, null);
holder = new ViewHolder();
holder.text1=(TextView)convertView.findViewById(R.id.text1);
holder.text = (TextView) convertView.findViewById(R.id.text);
holder.icon = (ImageView) convertView.findViewById(R.id.icon);
convertView.setTag(holder);
}
else {
holder = (ViewHolder) convertView.getTag();
}
holder.text.setText(friends[position].userName);
holder.icon.setImageBitmap(friends[position].status == STATUS.ONLINE ? mOnlineIcon : mOfflineIcon);
return convertView;
}
}
public class MessageReceiver extends BroadcastReceiver {
@Override
public void onReceive(Context context, Intent intent) {
Log.i("Broadcast receiver ", "received a message");
Bundle extra = intent.getExtras();
if (extra != null)
{
String action = intent.getAction();
if (action.equals(IMService.FRIEND_LIST_UPDATED))
{
FriendList.this.updateData(FriendController.getFriendsInfo(),
FriendController.getUnapprovedFriendsInfo());
}
}
}
};
public MessageReceiver messageReceiver = new MessageReceiver();
private ServiceConnection mConnection = new ServiceConnection() {
public void onServiceConnected(ComponentName className, IBinder service) {
imService = ((IMService.IMBinder)service).getService();
FriendInfo[] friends = FriendController.getFriendsInfo();
if (friends != null) {
FriendList.this.updateData(friends, null);
}
setTitle(imService.getUsername() + "'s friend list");
ownusername = imService.getUsername();
}
public void onServiceDisconnected(ComponentName className) {
imService = null;
Toast.makeText(FriendList.this, R.string.local_service_stopped,
Toast.LENGTH_SHORT).show();
}
};
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.list_screen);
friendAdapter = new FriendListAdapter(this);
try {
String result1 = imService.DispalyGroupDetails(imService.getUsername());
System.out.println(result1);
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
}
public void updateData(FriendInfo[] friends, FriendInfo[] unApprovedFriends)
{
if (friends != null) {
friendAdapter.setFriendList(friends);
setListAdapter(friendAdapter);
}
if (unApprovedFriends != null)
{
NotificationManager NM = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
if (unApprovedFriends.length > 0)
{
String tmp = new String();
for (int j = 0; j < unApprovedFriends.length; j++) {
tmp = tmp.concat(unApprovedFriends[j].userName).concat(",");
}
NotificationCompat.Builder mBuilder = new NotificationCompat.Builder(this)
.setSmallIcon(R.drawable.stat_sample)
.setContentTitle(getText(R.string.new_friend_request_exist));
/*Notification notification = new Notification(R.drawable.stat_sample,
getText(R.string.new_friend_request_exist),
System.currentTimeMillis());*/
Intent i = new Intent(this, UnApprovedFriendList.class);
i.putExtra(FriendInfo.FRIEND_LIST, tmp);
PendingIntent contentIntent = PendingIntent.getActivity(this, 0,
i, 0);
mBuilder.setContentText("You have new friend request(s)");
mBuilder.setContentIntent(contentIntent);
NM.notify(R.string.new_friend_request_exist, mBuilder.build());
}
else
{
NM.cancel(R.string.new_friend_request_exist);
}
}
}
@Override
protected void onListItemClick(ListView l, View v, int position, long id) {
super.onListItemClick(l, v, position, id);
Intent i = new Intent(this, Messaging.class);
FriendInfo friend = friendAdapter.getItem(position);
i.putExtra(FriendInfo.USERNAME, friend.userName);
i.putExtra(FriendInfo.PORT, friend.port);
i.putExtra(FriendInfo.IP, friend.ip);
startActivity(i);
}
@Override
protected void onPause()
{
unregisterReceiver(messageReceiver);
unbindService(mConnection);
super.onPause();
}
@Override
protected void onResume()
{
super.onResume();
bindService(new Intent(FriendList.this, IMService.class), mConnection , Context.BIND_AUTO_CREATE);
IntentFilter i = new IntentFilter();
i.addAction(IMService.FRIEND_LIST_UPDATED);
registerReceiver(messageReceiver, i);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
boolean result = super.onCreateOptionsMenu(menu);
menu.add(0, ADD_NEW_FRIEND_ID, 0, R.string.add_new_friend);
menu.add(0, CREATE_GROUP_ID, 0, R.string.create_group);
menu.add(0, EXIT_APP_ID, 0, R.string.exit_application);
return result;
}
@Override
public boolean onMenuItemSelected(int featureId, MenuItem item)
{
switch(item.getItemId())
{
case ADD_NEW_FRIEND_ID:
{
Intent i = new Intent(FriendList.this, AddFriend.class);
startActivity(i);
return true;
}
case CREATE_GROUP_ID:
{
Intent i = new Intent(FriendList.this, CreateGroup.class);
startActivity(i);
return true;
}
case EXIT_APP_ID:
{
imService.exit();
finish();
return true;
}
}
return super.onMenuItemSelected(featureId, item);
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
}
}
logcat的
02-07 05:17:54.526: E/AndroidRuntime(3081): FATAL EXCEPTION: main
02-07 05:17:54.526: E/AndroidRuntime(3081): Process: at.vcity.androidim, PID: 3081
02-07 05:17:54.526: E/AndroidRuntime(3081): java.lang.RuntimeException: Unable to start activity ComponentInfo{at.vcity.androidim/at.vcity.androidim.FriendList}: java.lang.NullPointerException
02-07 05:17:54.526: E/AndroidRuntime(3081): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
02-07 05:17:54.526: E/AndroidRuntime(3081): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
02-07 05:17:54.526: E/AndroidRuntime(3081): at android.app.ActivityThread.access$800(ActivityThread.java:135)
02-07 05:17:54.526: E/AndroidRuntime(3081): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
02-07 05:17:54.526: E/AndroidRuntime(3081): at android.os.Handler.dispatchMessage(Handler.java:102)
02-07 05:17:54.526: E/AndroidRuntime(3081): at android.os.Looper.loop(Looper.java:136)
02-07 05:17:54.526: E/AndroidRuntime(3081): at android.app.ActivityThread.main(ActivityThread.java:5017)
02-07 05:17:54.526: E/AndroidRuntime(3081): at java.lang.reflect.Method.invokeNative(Native Method)
02-07 05:17:54.526: E/AndroidRuntime(3081): at java.lang.reflect.Method.invoke(Method.java:515)
02-07 05:17:54.526: E/AndroidRuntime(3081): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
02-07 05:17:54.526: E/AndroidRuntime(3081): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
02-07 05:17:54.526: E/AndroidRuntime(3081): at dalvik.system.NativeStart.main(Native Method)
02-07 05:17:54.526: E/AndroidRuntime(3081): Caused by: java.lang.NullPointerException
02-07 05:17:54.526: E/AndroidRuntime(3081): at at.vcity.androidim.FriendList.onCreate(FriendList.java:178)
02-07 05:17:54.526: E/AndroidRuntime(3081): at android.app.Activity.performCreate(Activity.java:5231)
02-07 05:17:54.526: E/AndroidRuntime(3081): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
02-07 05:17:54.526: E/AndroidRuntime(3081): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
02-07 05:17:54.526: E/AndroidRuntime(3081): ... 11 more