Access external storage in File Chooser

I am trying to implement a File Chooser. I am using Android File Explore for file chooser in my app. When I run the app, it shows me Internal storage and returns me the file path, but it doesn't show External Storage at all.

This is my AndroidManifest.xml file.

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.unicloud.mittal" >

    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.GET_ACCOUNTS" />
    <uses-permission android:name="android.permission.USE_CREDENTIALS" />
    <uses-permission android:name="android.permission.MANAGE_DOCUMENTS" />
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:logo="@drawable/ic_launcher"
        android:theme="@style/AppTheme" >
        <meta-data
            android:name="com.google.android.gms.version"
            android:value="@integer/google_play_services_version" />

        <activity
            android:name=".Splash"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity
            android:name=".loginWithGooglePlus"
            android:label="@string/app_name"
            android:logo="@drawable/ic_launcher" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.DEFAULT" />
            </intent-filter>
        </activity>
        <activity
            android:name=".FileExplore"
            android:label="Pick a file"
            android:permission="android.permission.MANAGE_DOCUMENTS" >
            <intent-filter>
                <action android:name="android.content.action.DOCUMENTS_PROVIDER" />
            </intent-filter>

        </activity>
    </application>

</manifest>

Where I am doing wrong?

In the above github link you are using Environment.getExternalStorageDirectory() API which is working as expected. I think you misunderstood the use of this API. This API will always return the primary external storage directory. Below explanation may help you:

First of all, What is difference between Internal Storage, External Storage (aka primary external storage) and Secondary External Storage?

Internal Storage: is storage that is not accessible by the user, except via installed apps (or by rooting their device). Example: data/data/app_packageName

Primary External Storage: In built shared storage which is "accessible by the user by plugging in a USB cable and mounting it as a drive on a host computer". Example: When we say Nexus 5 32 GB.

Secondary External Storage: Removable storage. Example: SD Card.

Now next question. How to access SD card in Lollipop? To access SD card Android introduced new Storage Access Framework in KitKat.

Here is one answer explained it beautifully: https://stackoverflow.com/a/26765884/631803