PopupWindow之前已经学习过了，可以查看教程[
​​​PopupWindow的一些干货​​

先做个简单效果：PopupWindow显示在按钮下方

PopupwindowActivity

public class PopupwindowActivity extends AppCompatActivity {
    PopupWindow popupWindow;
    Button btn_add;

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

        btn_add = findViewById(R.id.btn_add);
        btn_add.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                //popupwindow的布局
                View popupView = View.inflate(PopupwindowActivity.this,R.layout.layout_more,null);
                popupWindow = new PopupWindow(popupView, ViewGroup.LayoutParams.WRAP_CONTENT,ViewGroup.LayoutParams.WRAP_CONTENT);
                //根据点击的view显示
                popupWindow.showAsDropDown(view,0,0);
            }
        });
    }
}

布局activity_popupwindow即一个Button

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:gravity="center">

    <Button
        android:id="@+id/btn_add"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="添加好友"/>

</LinearLayout>

PopupWindow的布局layout_more中包含2个Button

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical">

    <Button
        android:id="@+id/btn_add_by_contact"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="通讯录"/>
    <Button
        android:id="@+id/btn_add_by_qq"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Q  Q"/>

</LinearLayout>

让PopupWindow显示在Button上面

//popupwindow的布局
                View popupView = View.inflate(PopupwindowActivity.this,R.layout.layout_more,null);
                popupWindow = new PopupWindow(popupView, ViewGroup.LayoutParams.WRAP_CONTENT,ViewGroup.LayoutParams.WRAP_CONTENT);
                //添加好友的按钮已经显示出来了，所以直接调用getHeight()即可拿到高度
                int btnHeight = btn_add.getHeight();
                //而弹出的view并没有显示出来，所以调用getMeasuredHeight()来得到高度
                popupView.measure(0,0);
                int viewHeight = popupView.getMeasuredHeight();
                int yoff = btnHeight+viewHeight;
                popupWindow.showAsDropDown(view,0,-yoff);

现在实现点击弹出的PopupWindow使其消失

if (popupWindow == null) {
                    //popupwindow的布局
                    final View popupView = View.inflate(PopupwindowActivity.this, R.layout.layout_more, null);
                    ......
                    popupWindow.showAsDropDown(view, 0, -yoff);

                    Button btnAddContact = popupView.findViewById(R.id.btn_add_by_contact);
                    btnAddContact.setOnClickListener(new View.OnClickListener() {
                        @Override
                        public void onClick(View view) {
                            popupWindow.dismiss();
                            popupWindow = null;
                        }
                    });
                }