Android開發(fā)如何使用PopupWindow實現(xiàn)加載等待界面

<&#63;xml version="1.0" encoding="utf-8"&#63;>
<LinearLayout
 xmlns:android="http://schemas.android.com/apk/res/android"
 xmlns:tools="http://schemas.android.com/tools"
 android:id="@+id/activity_main"
 android:layout_width="match_parent"
 android:layout_height="match_parent"
 android:paddingBottom="@dimen/activity_vertical_margin"
 android:paddingLeft="@dimen/activity_horizontal_margin"
 android:paddingRight="@dimen/activity_horizontal_margin"
 android:paddingTop="@dimen/activity_vertical_margin"
 android:orientation="vertical"
 tools:context="com.toprs.myapplication.MainActivity">

 <Button
  android:text="登錄"
  android:layout_width="match_parent"
  android:layout_height="wrap_content"
  android:onClick="loginClick"
  android:id="@+id/button2"/>
</LinearLayout>

package com.wang.myapplication;

import ...

public class MainActivity extends AppCompatActivity {

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

 public void loginClick(View v){
  final PopupWindow popupWindow = new PopupWindow();
  popupWindow.setHeight(ViewGroup.LayoutParams.WRAP_CONTENT);
  popupWindow.setWidth(ViewGroup.LayoutParams.WRAP_CONTENT);
  popupWindow.setFocusable(true);
  View view = LayoutInflater.from(this).inflate(R.layout.popup,null);
  popupWindow.setContentView(view);
  popupWindow.showAtLocation(getWindow().getDecorView(), Gravity.CENTER,0,0);

  new Handler().postDelayed(new Runnable() {
   @Override
   public void run() {
    Toast.makeText(MainActivity.this, "登錄成功", Toast.LENGTH_SHORT).show();
    popupWindow.dismiss();
   }
  },2000);
 }
}

<&#63;xml version="1.0" encoding="utf-8"&#63;>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="200dp"
    android:layout_height="200dp">

 <ProgressBar
  android:id="@+id/progressBar4"
  
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  android:layout_centerInParent="true"/>

</RelativeLayout>