我需要一段代码：android studio添加好友到sqLite数据库中，并显示好友列表

好的，以下是一个简单的示例代码，可以将好友添加到SQLite数据库中，并显示好友列表：

首先，在布局文件中添加一个ListView组件用于显示好友列表：

<ListView
    android:id="@+id/listView"
    android:layout_width="match_parent"
    android:layout_height="wrap_content" />

然后，在Activity中定义好友类和SQLite数据库辅助类：

public class Friend {
    private int id;
    private String name;

    public Friend() {}

    public Friend(String name) {
        this.name = name;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

public class DBHelper extends SQLiteOpenHelper {
    private static final String DATABASE_NAME = "friends.db";
    private static final int DATABASE_VERSION = 1;

    public DBHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL("CREATE TABLE friends (_id INTEGER PRIMARY KEY AUTOINCREMENT, name TEXT);");
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        db.execSQL("DROP TABLE IF EXISTS friends;");
        onCreate(db);
    }
}

接下来，在Activity中实现添加好友和显示好友列表的功能：

public class MainActivity extends AppCompatActivity {
    private DBHelper dbHelper;
    private List<Friend> friendList;
    private FriendAdapter friendAdapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        dbHelper = new DBHelper(this);

        friendList = new ArrayList<>();
        friendAdapter = new FriendAdapter(this, friendList);

        ListView listView = findViewById(R.id.listView);
        listView.setAdapter(friendAdapter);

        Button addButton = findViewById(R.id.addButton);
        addButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                EditText nameEditText = findViewById(R.id.nameEditText);
                String name = nameEditText.getText().toString();
                if (!TextUtils.isEmpty(name)) {
                    Friend friend = new Friend(name);
                    addFriend(friend);
                    friendAdapter.add(friend);
                    nameEditText.setText("");
                }
            }
        });

        loadFriends();
    }

    private void addFriend(Friend friend) {
        SQLiteDatabase db = dbHelper.getWritableDatabase();
        ContentValues values = new ContentValues();
        values.put("name", friend.getName());
        db.insert("friends", null, values);
        db.close();
    }

    private void loadFriends() {
        SQLiteDatabase db = dbHelper.getReadableDatabase();
        Cursor cursor = db.query("friends", null, null, null, null, null, null);
        if (cursor.moveToFirst()) {
            do {
                int id = cursor.getInt(cursor.getColumnIndex("_id"));
                String name = cursor.getString(cursor.getColumnIndex("name"));
                Friend friend = new Friend(name);
                friend.setId(id);
                friendList.add(friend);
            } while (cursor.moveToNext());
        }
        cursor.close();
        db.close();
    }

    private static class FriendAdapter extends ArrayAdapter<Friend> {
        private LayoutInflater inflater;

        public FriendAdapter(Context context, List<Friend> objects) {
            super(context, 0, objects);
            inflater = LayoutInflater.from(context);
        }

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            ViewHolder holder;
            if (convertView == null) {
                convertView = inflater.inflate(android.R.layout.simple_list_item_1, parent, false);
                holder = new ViewHolder(convertView);
                convertView.setTag(holder);
            } else {
                holder = (ViewHolder) convertView.getTag();
            }
            Friend friend = getItem(position);
            holder.nameTextView.setText(friend.getName());
            return convertView;
        }

        private static class ViewHolder {
            public TextView nameTextView;

            public ViewHolder(View view) {
                nameTextView = view.findViewById(android.R.id.text1);
            }
        }
    }
}

以上是一个简单的示例代码，可以将好友添加到SQLite数据库中，并显示好友列表。请根据实际需求进行修改和优化。