给GridView或ListView添加一个固定按钮（类似于微信群聊邀请好友按钮）

给GridView添加一个固定的尾部按钮，以及监听点击事件：（类似于微信群聊邀请好友按钮）
如下图效果：


想实现这个效果的话非常简单（关于GridView的基本用法我就不多说了）
粘贴关键代码：

@Override    public int getCount() {        return friendsBeans.size() + 1;    }

只需要在GridView的适配器的getCount()方法中的返回值+1，这样就会多制造一个View（就是size加1个View）。

@Override    public View getView(int position, View convertView, ViewGroup parent) {        ViewHolder viewHolder;        if (null == convertView) {            viewHolder = new ViewHolder();            convertView = LayoutInflater.from(context).inflate(R.layout.item_group_data, null);            viewHolder.ivPhoto = (ImageView) convertView.findViewById(R.id.iv1);            viewHolder.tvName = (TextView) convertView.findViewById(R.id.tv_name);            convertView.setTag(viewHolder);        } else {            viewHolder = (ViewHolder) convertView.getTag();        }        if (position < friendsBeans.size()) {            FriendsBean friendsBean = (FriendsBean) getItem(position);            viewHolder.tvName.setText(friendsBean.getName());            Glide.with(context).load(friendsBean.getPhoto()).into(viewHolder.ivPhoto);        } else {            viewHolder.ivPhoto.setImageBitmap(BitmapFactory.decodeResource(context.getResources(), R.drawable.add_btn));            viewHolder.tvName.setVisibility(View.GONE);        }        return convertView;    }    static class ViewHolder {        ImageView ivPhoto;        TextView tvName;    }

主要看这个部分：

if (position < friendsBeans.size()) {            FriendsBean friendsBean = (FriendsBean) getItem(position);            viewHolder.tvName.setText(friendsBean.getName());            Glide.with(context).load(friendsBean.getPhoto()).into(viewHolder.ivPhoto);        } else {            viewHolder.ivPhoto.setImageBitmap(BitmapFactory.decodeResource(context.getResources(), R.drawable.add_btn));            viewHolder.tvName.setVisibility(View.GONE);        }

这里在GridView的适配器的getView()方法中判断当前在给第几个View赋值如果是集合size范围之内的就按照正常的方法赋值，是size之外的也就是我们刚才加1的View的话就给ImageView设置特殊的图片（也就是➕号图片）。

下面是加号的点击事件监听：
给GridView设置监听器我就不写了，主要逻辑在这段代码中：

@Override    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {        if (parent.getChildCount() - 1 == position) {//点击了加号            Toast.makeText(this, "邀请好友", Toast.LENGTH_SHORT).show();        } else {            Toast.makeText(this, position + "", Toast.LENGTH_SHORT).show();        }    }

这里判断点击的子View是否为最后一个，然后把需要的逻辑方法写在里面就OK了。

下面是全部代码：

实体类：

public class FriendsBean {    private String photo;    private String name;    private boolean check;    public FriendsBean() {    }    public FriendsBean(String photo, String name, boolean check) {        this.photo = photo;        this.name = name;        this.check = check;    }    public String getPhoto() {        return photo;    }    public void setPhoto(String photo) {        this.photo = photo;    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public boolean getCheck() {        return check;    }    public void setCheck(boolean check) {        this.check = check;    }}

Activity类：

public class GroupDataActivity extends AppCompatActivity implements AdapterView.OnItemClickListener {    private MyGridView gridView;    private GroupDataAdapter groupDataAdapter;    private GroupDataPresenter groupDataPresenter;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_group_data);        initView();        initData();        setListeners();    }    private void setListeners() {        gridView.setOnItemClickListener(this);    }    private void initData() {        List<FriendsBean> fbs = new ArrayList<>();        fbs.add(new FriendsBean("https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1502876543133&di=ed2dbfd1848aaeed780366dc0544224d&imgtype=0&src=http%3A%2F%2Fwww.jintang.cn%2Fdata%2Fattachment%2Fportal%2F201412%2F13%2F100108x6jj2s802h8j3cob.jpg", "小松", false));        fbs.add(new FriendsBean("https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1502876763302&di=e1cde7fea3dba1c35fde549918b84886&imgtype=0&src=http%3A%2F%2Fhiphotos.baidu.com%2Fdoc%2Fpic%2Fitem%2F7acb0a46f21fbe09f67d698062600c338744ad07.jpg", "小井", false));        fbs.add(new FriendsBean("https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1502876791845&di=af6700b8381f5e696348f3da37109397&imgtype=0&src=http%3A%2F%2Fpic23.nipic.com%2F20120914%2F10910345_100020812000_2.jpg", "高小松", false));        fbs.add(new FriendsBean("https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1502876791845&di=217c1bfedac7191511cefb44242b10fa&imgtype=0&src=http%3A%2F%2Fpic24.nipic.com%2F20120921%2F10910345_130417417000_2.jpg", "欧阳峰", false));        fbs.add(new FriendsBean("https://gss3.bdstatic.com/7Po3dSag_xI4khGkpoWK1HF6hhy/baike/c0%3Dbaike80%2C5%2C5%2C80%2C26/sign=cfab9c942c9759ee5e5d6899d3922873/5d6034a85edf8db10c4284fd0323dd54564e743f.jpg", "东方不败", false));        fbs.add(new FriendsBean("https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1502876894676&di=fdc9301ca95f5d03b579b4b402892e0f&imgtype=0&src=http%3A%2F%2Fwww.qxjlm.com%2Ftupians%2Fbd12876292.jpg", "黄老邪", false));        fbs.add(new FriendsBean("https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1502876908257&di=61c2bbc1adecc3dd594c47e586fc599b&imgtype=jpg&src=http%3A%2F%2Fimg4.imgtn.bdimg.com%2Fit%2Fu%3D2580324790%2C489579783%26fm%3D214%26gp%3D0.jpg", "松", false));        fbs.add(new FriendsBean("https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1502876894668&di=f017e4596cda6278fe7eb5380720f94f&imgtype=0&src=http%3A%2F%2Fimg.faxingw.cn%2F201509%2F51m_13.jpg", "我去", false));        fbs.add(new FriendsBean("https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1502876894723&di=0af8c5e2728936e89d9ef72f5746eb55&imgtype=0&src=http%3A%2F%2Fimg003.21cnimg.com%2Fphotos%2Falbum%2F20140114%2Fm320%2FE94AA721DE7DBF46E23E92EF0592849E.jpeg", "来来来来", false));        fbs.add(new FriendsBean("https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1502876894714&di=ec94f48b042accc87997d1c223d01604&imgtype=0&src=http%3A%2F%2Fscimg.jb51.net%2Fallimg%2F151202%2F14-1512021A520Z2.jpg", "阿斯达撒上的", false));        fbs.add(new FriendsBean("https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1502876894710&di=e4a616663913bad5fd8fecf969254ace&imgtype=0&src=http%3A%2F%2Fimg3.duitang.com%2Fuploads%2Fitem%2F201509%2F14%2F20150914191741_rJXCw.thumb.700_0.png", "多少啊", false));        groupDataAdapter = new GroupDataAdapter(this, fbs);        gridView.setAdapter(groupDataAdapter);    }    private void initView() {        gridView = (MyGridView) findViewById(R.id.gridview);    }    @Override    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {        if (parent.getChildCount() - 1 == position) {//点击了加号            Toast.makeText(this, "邀请好友", Toast.LENGTH_SHORT).show();        } else {            Toast.makeText(this, position + "", Toast.LENGTH_SHORT).show();        }    }}

Adapter类：

public class GroupDataAdapter extends BaseAdapter {    private Context context;    private List<FriendsBean> friendsBeans;    public GroupDataAdapter(Context context, List<FriendsBean> friendsBeans) {        this.context = context;        this.friendsBeans = friendsBeans;    }    @Override    public int getCount() {        return friendsBeans.size() + 1;    }    @Override    public Object getItem(int position) {        return friendsBeans.get(position);    }    @Override    public long getItemId(int position) {        return position;    }    @Override    public View getView(int position, View convertView, ViewGroup parent) {        ViewHolder viewHolder;        if (null == convertView) {            viewHolder = new ViewHolder();            convertView = LayoutInflater.from(context).inflate(R.layout.item_group_data, null);            viewHolder.ivPhoto = (ImageView) convertView.findViewById(R.id.iv1);            viewHolder.tvName = (TextView) convertView.findViewById(R.id.tv_name);            convertView.setTag(viewHolder);        } else {            viewHolder = (ViewHolder) convertView.getTag();        }        if (position < friendsBeans.size()) {            FriendsBean friendsBean = (FriendsBean) getItem(position);            viewHolder.tvName.setText(friendsBean.getName());            Glide.with(context).load(friendsBean.getPhoto()).into(viewHolder.ivPhoto);        } else {            viewHolder.ivPhoto.setImageBitmap(BitmapFactory.decodeResource(context.getResources(), R.drawable.add_btn));            viewHolder.tvName.setVisibility(View.GONE);        }        return convertView;    }    static class ViewHolder {        ImageView ivPhoto;        TextView tvName;    }

以上就是全部代码，（如有遗漏或错误请留言讨论）。