WhatsApp chats can be transferred from Android to iPhone, you can search "Transfer WhatsApp messages between Android and iPhone" on Google, and there are numerous results, and some are reliable and workable, such as WhatsMate, a WhatsApp Data Manager tool.
You said you have backed up Android WhatsApp, does it mean that you backup WhatsApp messages with the built-in backup function? If so, I'm afraid that even if you have this backup file to your iPhone, the messages still can't be restore to iPhone WhatsApp.
Since it is a cross-platform operation, you need help from some professional tools which aim at transferring WhatsApp messages between different platform devices.
— modified on Jun 27, 2017 5:44:08 AM