安卓自定义Dialog

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    >
<LinearLayout
    android:background="#000"
    android:layout_gravity="center_horizontal"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:gravity="center_horizontal">
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textColor="#fff"
        android:textSize="24dp"
        android:text="自定义Dailog"/>
</LinearLayout>
<LinearLayout
    android:layout_gravity="center"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="wrap_content">
    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="20dp"
        android:id="@+id/messg"
        android:text="测试内容"
        android:gravity="center_horizontal" />
</LinearLayout>
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="确认"
        android:id="@+id/qr"
        android:layout_gravity="center_horizontal" />

</LinearLayout>

public class MainActivity extends AppCompatActivity {
private Button bt1;
    private Button qr;
    Dialog dailog;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        bt1= (Button) findViewById(R.id.button);
        bt1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                LayoutInflater inflater=LayoutInflater.from(MainActivity.this);
                View dai=inflater.inflate(R.layout.test,null);
                final AlertDialog.Builder builder=new AlertDialog.Builder(MainActivity.this);
                builder.setView(dai);
               dai.findViewById(R.id.qr).setOnClickListener(new View.OnClickListener() {
                   @Override
                   public void onClick(View view) {
                       dailog.dismiss();
                   }
               });
                dailog=builder.create();
                dailog.show();
            }
        });
    }
}