How to take screenshot programmatically in Android

Here I share Android source code to take a screenshot of whole screen and save it in device gallery. There is two buttons, one for taking screenshot and the second for opening last screenshot.

Permission:

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

MainActivity:

package com.zofiakreasi.myapplication;

import android.content.ContentValues;
import android.content.Context;
import android.content.Intent;
import android.graphics.Bitmap;
import android.net.Uri;
import android.os.Environment;
import android.provider.MediaStore;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

import java.io.File;
import java.io.FileOutputStream;
import java.util.Date;

public class MainActivity extends AppCompatActivity {

    Button button;
    Button button2;
    String folderName = "FolderName";

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

        button = (Button) findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                takeScreenshot();
            }
        });

        button2 = (Button) findViewById(R.id.button2);
        button2.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                openLastShot();
            }
        });

    }

    private void takeScreenshot(){
        Date now = new Date();
        android.text.format.DateFormat.format("yyyy-MM-dd_hh:mm:ss", now);

        try{
            File f = new File(Environment.getExternalStorageDirectory(), folderName);
            if(!f.exists()) f.mkdirs();
            String mPath = Environment.getExternalStorageDirectory().toString() + "/" + folderName + "/" + now + ".jpg";
            View v1 = getWindow().getDecorView().getRootView();
            v1.setDrawingCacheEnabled(true);
            Bitmap bitmap = Bitmap.createBitmap(v1.getDrawingCache());
            v1.setDrawingCacheEnabled(false);

            File imageFile = new File(mPath);
            FileOutputStream outputStream = new FileOutputStream(imageFile);
            int quality = 100;
            bitmap.compress(Bitmap.CompressFormat.JPEG, quality, outputStream);
            outputStream.flush();
            outputStream.close();

            addToGallery(mPath, this);
            openScreenshot(imageFile);
        } catch (Throwable e) {
            e.printStackTrace();
        }
    }

    private void openScreenshot(File imageFile){
        Intent intent = new Intent();
        intent.setAction(Intent.ACTION_VIEW);
        Uri uri = Uri.fromFile(imageFile);
        intent.setDataAndType(uri, "image/*");
        Toast.makeText(this, imageFile.getAbsolutePath(), Toast.LENGTH_LONG).show();
        startActivity(intent);
    }

    private void openLastShot(){
        String mPath = Environment.getExternalStorageDirectory().toString() + "/" + folderName + "/";
        File dir = new File(mPath);
        File[] files = dir.listFiles();
        if(files.length == 0) Toast.makeText(this, "No shot found!", Toast.LENGTH_LONG).show();
        else openScreenshot(files[files.length-1]);
    }

    private void addToGallery(String filePath, Context context){
        ContentValues values = new ContentValues();
        values.put(MediaStore.Images.Media.DATE_TAKEN, System.currentTimeMillis());
        values.put(MediaStore.Images.Media.MIME_TYPE, "image/jpeg");
        values.put(MediaStore.MediaColumns.DATA, filePath);
        context.getContentResolver().insert(MediaStore.Images.Media.EXTERNAL_CONTENT_URI, values);
    }
}

activity_main.xml :

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    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"
    tools:context="com.zofiakreasi.myapplication.MainActivity">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Take Screenshot"
        android:id="@+id/button"
        android:layout_centerVertical="true"
        android:layout_centerHorizontal="true" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Open Last Shot"
        android:id="@+id/button2"
        android:layout_below="@+id/button"
        android:layout_centerHorizontal="true" />
</RelativeLayout>

This source code is mix of two tutorials and I did little bit changes. Here is original source:
https://stackoverflow.com/questions/2661536/how-to-programmatically-take-a-screenshot-in-android
https://stackoverflow.com/questions/20859584/how-to-save-image-in-android-gallery