Display activity as dialog

1) package com.example.manisha.myapplication;

import android.app.Activity;
import android.os.Bundle;
import android.util.DisplayMetrics;
import android.view.ViewGroup;
import android.view.ViewGroup.LayoutParams;
import android.view.Window;

/** * Created by Manisha on 7/29/2017. */
public class NewActivity extends Activity {
    protected void onCreate(Bundle savedInstanceState) {

        requestWindowFeature(Window.FEATURE_NO_TITLE);
super.onCreate(savedInstanceState);

        DisplayMetrics metrics = getResources().getDisplayMetrics();
        int screenWidth = (int) (metrics.widthPixels * 0.90);
        int screenHeight = (int) (metrics.heightPixels * 0.80);

        setContentView(R.layout.new_activity);

        getWindow().setLayout(screenWidth, screenHeight);
//        getWindow().setLayout(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT);
    }
}

in manifest 

<activity android:name=".NewActivity" android:theme="@android:style/Theme.Dialog">

</activity>