showDialog(MainActivity.this, "title", "message", "OK", "Cancel", {...}, {...});
Kotlin
fun showDialog(context: Context, title: String, msg: String,
               positiveBtnText: String, negativeBtnText: String?,
               positiveBtnClickListener: DialogInterface.OnClickListener,
               negativeBtnClickListener: DialogInterface.OnClickListener?): AlertDialog {
    val builder = AlertDialog.Builder(context)
            .setTitle(title)
            .setMessage(msg)
            .setCancelable(true)
            .setPositiveButton(positiveBtnText, positiveBtnClickListener)
    if (negativeBtnText != null)
        builder.setNegativeButton(negativeBtnText, negativeBtnClickListener)
    val alert = builder.create()
    alert.show()
    return alert
}
Java
public static AlertDialog showDialog(@NonNull Context context, @NonNull String title, @NonNull String msg,
                                     @NonNull String positiveBtnText, @Nullable String negativeBtnText,
                                     @NonNull DialogInterface.OnClickListener positiveBtnClickListener,
                                     @Nullable DialogInterface.OnClickListener negativeBtnClickListener) {
    AlertDialog.Builder builder = new AlertDialog.Builder(context)
            .setTitle(title)
            .setMessage(msg)
            .setCancelable(true)
            .setPositiveButton(positiveBtnText, positiveBtnClickListener);
    if (negativeBtnText != null)
        builder.setNegativeButton(negativeBtnText, negativeBtnClickListener);
    AlertDialog alert = builder.create();
    alert.show();
    return alert;
}