StyleableToast

Library on GitHub with installation instructions:

github.com/Muddz/StyleableToast

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.codinginflow.styleabletoastexample.MainActivity">

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="showToast"
        android:text="Show Toast"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</android.support.constraint.ConstraintLayout>

package com.codinginflow.styleabletoastexample;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;

import com.muddzdev.styleabletoastlibrary.StyleableToast;

public class MainActivity extends AppCompatActivity {

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

    public void showToast(View v) {
        StyleableToast.makeText(this, "Hello World!", R.style.exampleToast).show();
    }
}

<resources>

    <!-- Base application theme. -->
    <style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
        <!-- Customize your theme here. -->
        <item name="colorPrimary">@color/colorPrimary</item>
        <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
        <item name="colorAccent">@color/colorAccent</item>
    </style>

    <style name="exampleToast">
        <item name="colorBackground">#94ffab</item>
        <item name="textColor">#000</item>
        <item name="iconLeft">@drawable/ic_android</item>
        <item name="strokeColor">#000</item>
        <item name="strokeWidth">3dp</item>
        <item name="length">LONG</item>
        <item name="cornerRadius">3dp</item>
    </style>

</resources>