在Searchbox.addTextChangedListener(new TextWatcher()中的@Override public void onTextChanged(CharSequence charSequence, int i, int i1, int i2) 中，这段代码哪错了Cursor cursor=db2.rawQuery("select*from student_course where scname like '%?%'",new String[]{(String) charSequence});

这段代码的问题在于在 SQL 查询中使用了单引号来括住参数占位符 "?"，这会导致参数占位符被视为字符串常量，而不是查询中的参数。因此，应该将单引号从参数占位符中移除，同时在查询参数字符串中包含百分号，如下所示：

Cursor cursor = db2.rawQuery("SELECT * FROM student_course WHERE scname LIKE ?", new String[]{"%" + charSequence + "%"});

这样，查询参数字符串将被正确地拼接到 SQL 查询中，而不会被视为字符串常量。

相关问题

android 好友功能,Android中使用ListView模拟微信好友功能代码

好的，以下是一个简单的Android使用ListView模拟微信好友功能的代码示例：

Friend.java（好友数据模型类）：

public class Friend {
    private int avatarId;
    private String nickname;
    private String remark;

    public Friend(int avatarId, String nickname, String remark) {
        this.avatarId = avatarId;
        this.nickname = nickname;
        this.remark = remark;
    }

    public int getAvatarId() {
        return avatarId;
    }

    public void setAvatarId(int avatarId) {
        this.avatarId = avatarId;
    }

    public String getNickname() {
        return nickname;
    }

    public void setNickname(String nickname) {
        this.nickname = nickname;
    }

    public String getRemark() {
        return remark;
    }

    public void setRemark(String remark) {
        this.remark = remark;
    }
}

friend_item.xml（好友列表项布局文件）：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="80dp"
    android:paddingLeft="16dp"
    android:paddingRight="16dp"
    android:paddingTop="8dp"
    android:paddingBottom="8dp"
    android:background="@android:color/white">

    <ImageView
        android:id="@+id/avatar"
        android:layout_width="60dp"
        android:layout_height="60dp"
        android:layout_alignParentLeft="true"/>

    <TextView
        android:id="@+id/nickname"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="18sp"
        android:textColor="@android:color/black"
        android:layout_toRightOf="@+id/avatar"
        android:layout_marginLeft="16dp"
        android:layout_centerVertical="true"/>

    <TextView
        android:id="@+id/remark"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="14sp"
        android:textColor="@android:color/darker_gray"
        android:layout_toRightOf="@+id/avatar"
        android:layout_below="@+id/nickname"
        android:layout_marginLeft="16dp"/>

</RelativeLayout>

FriendAdapter.java（好友列表适配器）：

public class FriendAdapter extends BaseAdapter implements SectionIndexer {
    private List<Friend> friendList;
    private Context context;
    private LayoutInflater inflater;

    public FriendAdapter(List<Friend> friendList, Context context) {
        this.friendList = friendList;
        this.context = context;
        inflater = LayoutInflater.from(context);
    }

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

    @Override
    public Object getItem(int position) {
        return friendList.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.friend_item, parent, false);
            holder = new ViewHolder();
            holder.avatar = convertView.findViewById(R.id.avatar);
            holder.nickname = convertView.findViewById(R.id.nickname);
            holder.remark = convertView.findViewById(R.id.remark);
            convertView.setTag(holder);
        } else {
            holder = (ViewHolder) convertView.getTag();
        }

        Friend friend = friendList.get(position);
        holder.avatar.setImageResource(friend.getAvatarId());
        holder.nickname.setText(friend.getNickname());
        holder.remark.setText(friend.getRemark());

        return convertView;
    }

    @Override
    public Object[] getSections() {
        return new Object[0];
    }

    @Override
    public int getPositionForSection(int sectionIndex) {
        for (int i = 0; i < getCount(); i++) {
            String nickname = friendList.get(i).getNickname();
            String firstLetter = String.valueOf(nickname.charAt(0)).toUpperCase();
            if (firstLetter.charAt(0) == sectionIndex) {
                return i;
            }
        }
        return -1;
    }

    @Override
    public int getSectionForPosition(int position) {
        String nickname = friendList.get(position).getNickname();
        String firstLetter = String.valueOf(nickname.charAt(0)).toUpperCase();
        return firstLetter.charAt(0);
    }

    private static class ViewHolder {
        ImageView avatar;
        TextView nickname;
        TextView remark;
    }
}

MainActivity.java（主界面代码）：

public class MainActivity extends AppCompatActivity implements TextWatcher {
    private EditText searchBox;
    private ListView friendListView;
    private FriendAdapter friendAdapter;
    private List<Friend> friendList;
    private List<Friend> filteredFriendList;

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

        searchBox = findViewById(R.id.search_box);
        friendListView = findViewById(R.id.friend_list);

        friendList = new ArrayList<>();
        friendList.add(new Friend(R.drawable.avatar1, "张三", "三哥"));
        friendList.add(new Friend(R.drawable.avatar2, "李四", "四哥"));
        friendList.add(new Friend(R.drawable.avatar3, "王五", "五哥"));
        friendList.add(new Friend(R.drawable.avatar4, "赵六", "六哥"));
        friendList.add(new Friend(R.drawable.avatar5, "钱七", "七哥"));
        friendList.add(new Friend(R.drawable.avatar6, "孙八", "八哥"));
        friendList.add(new Friend(R.drawable.avatar7, "周九", "九哥"));
        friendList.add(new Friend(R.drawable.avatar8, "吴十", "十哥"));

        friendAdapter = new FriendAdapter(friendList, this);
        friendListView.setAdapter(friendAdapter);

        searchBox.addTextChangedListener(this);
    }

    @Override
    public void beforeTextChanged(CharSequence s, int start, int count, int after) {

    }

    @Override
    public void onTextChanged(CharSequence s, int start, int before, int count) {
        filteredFriendList = new ArrayList<>();
        for (Friend friend : friendList) {
            if (friend.getNickname().contains(s)) {
                filteredFriendList.add(friend);
            }
        }
        friendAdapter = new FriendAdapter(filteredFriendList, this);
        friendListView.setAdapter(friendAdapter);
    }

    @Override
    public void afterTextChanged(Editable s) {

    }
}

以上代码仅供参考，具体实现还需要根据需要进行调整。