嗨，在下面的代码中如何获取imservice.getusername（）。但是，它给出了以下错误。我想要用户名，我正在写这个code.imservice.getusername（）这个相同像我正在访问它正在使用的用户名。但是在这个课程中它没有用。
任何人都可以在我错误的地方帮助我。
** 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.text1.setText(friends[position].groupName);
holder.icon.setImageBitmap(friends[position].status == STATUS.ONLINE ? mOnlineIcon : mOfflineIcon);
return convertView;
}
}
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();
}
}
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
** GroupList **
public class GroupList extends ListActivity
{
boolean[] checkBoxState;
boolean isChecked;
String check;
ListView users;
int position;
private IAppManager imService = null;
ArrayList<FriendInfo> result = new ArrayList<FriendInfo>();
private FriendListAdapter friendAdapter;
public String ownusername = new String();
private class FriendListAdapter extends BaseAdapter
{
@SuppressWarnings("unused")
class ViewHolder {
TextView text;
ImageView icon;
CheckBox check1;
}
private LayoutInflater mInflater;
private Bitmap mOnlineIcon;
private Bitmap mOfflineIcon;
private FriendInfo[] friend = 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.friend = friends;
}
public int getCount() {
return friend.length;
}
public FriendInfo getItem(int position) {
return friend[position];
}
public long getItemId(int position) {
return 0;
}
@SuppressWarnings("unused")
public View getView(final int position, View convertView, ViewGroup parent) {
final ViewHolder holder;
if (convertView == null)
{
convertView = mInflater.inflate(R.layout.grouplist, null);
holder = new ViewHolder();
holder.text = (TextView) convertView.findViewById(R.id.text);
holder.icon = (ImageView) convertView.findViewById(R.id.icon);
holder.check1 = (CheckBox)convertView.findViewById(R.id.checkBox1);
convertView.setTag(holder);
}
else {
holder = (ViewHolder) convertView.getTag();
}
holder.text.setText(friend[position].userName);
holder.icon.setImageBitmap(friend[position].status == STATUS.ONLINE ? mOnlineIcon : mOfflineIcon);
final ArrayList<String> checkedFriends = new ArrayList<String>();
checkBoxState = new boolean[friend.length];
holder.check1.setChecked(checkBoxState[position]);
holder.check1.setOnCheckedChangeListener(new OnCheckedChangeListener(){
public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
checkBoxState[position]=isChecked;
if(isChecked){
check=friend[position].userName;
}
}
});
return convertView;
}
protected void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
if (android.os.Build.VERSION.SDK_INT > 9) {
StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder()
.permitAll().build();
StrictMode.setThreadPolicy(policy);
}
setContentView(R.layout.group_list_screen);
Button create=(Button)findViewById(R.id.create);
friendAdapter = new FriendListAdapter(this);
friendAdapter.getCheckedItems();
create.setOnClickListener(new OnClickListener() {
@SuppressWarnings({ "unused", "unchecked" })
@Override
public void onClick(View v) {
String groupname = getIntent().getStringExtra("nick");
try {
String result1 = imService.CreateGroup(groupname,imService.getUsername(),friendAdapter.getCheckedItems());
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
Toast.makeText(getApplicationContext(), "Group Created Sucessfully",Toast.LENGTH_LONG).show();
}
});
}
答案 0 :(得分：0)
看起来你没有imService实例化，所以每次在imService上调用getter方法时，你都会得到空指针异常。