Safe getScrollResponder

[yury]

In our app redux can switch navigation when input is in focus.
When this happen we get crash:

TypeError
undefined is not an object (evaluating 'this.refs._rnkasv_keyboardView.getScrollResponder')

This PR make getScrollResponder a little bit safer.

[Swordsman-Inaction]

It does look safer with this changes, but I'd like to know why this.refs._rnkasv_keyboardView becomes undefined.

[yury]

I think it is in setTimeout thing. Sorry do not have full stacktrace.

…

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On Apr 5, 2017, at 6:22 AM, Swordsman-Inaction ***@***.***> wrote: It does look safer with this changes, but I'd like to know why this.refs._rnkasv_keyboardView becomes undefined. — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub, or mute the thread.

[Swordsman-Inaction]

@yury
Hi, I created a demo with the code below. A new scene would be open while the TextInput is still in focus, but cannot reproduce the error. Can you help me to find the cause?

import React, { Component } from 'react';
import ReactNative, {
  View,
  Text,
  TextInput,
} from 'react-native';
import { StackNavigator } from 'react-navigation';
import { KeyboardAwareScrollView } from 'react-native-keyboard-aware-scroll-view';

export class First extends Component {

  static navigationOptions = {
    title: 'First',
  }

  constructor(props) {
    super(props);

    this.onChangeText = this.onChangeText.bind(this);
  }

  onChangeText(text) {
    if (text === '123') {
      this.props.navigation.navigate('Second');
    }
  }

  render() {
    return (
      <KeyboardAwareScrollView extraHeight={80}>
        <TextInput style={{height: 44, marginTop: 500, backgroundColor: 'green'}} onChangeText={this.onChangeText} />
      </KeyboardAwareScrollView>
    );
  }
}

class Second extends Component {

  static navigationOptions = {
    title: 'Second',
  };

  render() {
    return (
      <Text>Test</Text>
    );
  }

}

const AppContainer = StackNavigator({
  First: { screen: First },
  Second: { screen: Second },
});

export default AppContainer;

[yury]

@Swordsman-Inaction

This is minimal repo I came up with.

It is something with linking...

Here is the video

Better to run device in release configuration.

Not 100% reproducible every time. But it happens from time to time.

[Swordsman-Inaction]

@yury Awesome!!! I debugged with your code, and I already find the cause.

• After the App is resumed from the Deep link, the keyboard would show again, and the updateKeyboardSpace would be called again.
• We are using async functions which are UIManager.viewIsDescendantOf, UIManager.measureInWindow and a timeout in scrollToFocusedInput.
• Before those async functions finish their job, the App will start handling the deep link in _handleOpenURL which replaces the Screen1 with Screen3 . So KeyboardAwareScrollView would be unmount for sure.
• After those async functions finish their job, the KeyboardAwareScrollView doesn't exist anymore which causes this error.
• The reason it's not 100% reproducible is sometimes those async functions are too slow, so UIManager.viewIsDescendantOf and UIManager.measureInWindow would fail because the component doesn't exist and the app would only give a warning in console, or those async functions finished their job before the component is unmounted so nothing happens.

So we found the cause :) ! This PR could prevent the app from crashing for sure, but it also covers the real problem we have. The solution for this could be adding unmount-checking in the callbacks.

Would you like to update this PR or create another PR to solve the problem?

[yury]

This isMounted?

[Swordsman-Inaction]

@yury Yes, I know it looks bad. I thought about doing some clean in the willUnmount function, but I cannot find a good way to cancel the callbacks. But we can use clearTimeout() for that timeout. It would be great if you have a better way to do it.

[alvaromb]

In the meantime, I think this PR makes sense.

[yury]

I looked at react native FlatList they do similar thing thing

PS: Do you plan to refactor and do not use mixins?

[alvaromb]

@yury yes, it's on my roadmap but I'm busy as hell right now.