React Native Picker moves back to first item

Question

This works as expected, where the picker stays on the selected item...

<Picker
    selectedValue={this.state.person}
    onValueChange={(itemValue) => this.setState({person: itemValue})}
    style={styles.picker}>
    {Object.keys(coWorkers)
        .map((result, index) =>
            <Picker.Item
                label={`${coWorkers[result].name}(${coWorkers[result].likes})`}
                value={coWorkers[result].name}
                key={index}
            />
        )
    }
</Picker>

I want to get multiple key/values from the coWorkers object in this.setState, so I am trying this...

<Picker
    selectedValue={this.state.person}
    onValueChange={(itemValue) => this.setState({person: itemValue.name, likes: itemValue.likes})}
    style={styles.picker}>
    {Object.keys(coWorkers)
        .map((result, index) =>
            <Picker.Item
                label={`${coWorkers[result].name} (${coWorkers[result].likes})`}
                value={coWorkers[result]}
                key={index}
            />
        )
    }
</Picker>

However, now the picker jumps back to the top (this.state is being correctly updated though).

Cowden

Answer 1

The type of the prop value for the Picker should be either string or integer. It is not clear from the docs on the website but you can see it in the Picker source code comments here https://github.com/facebook/react-native/blob/master/Libraries/Components/Picker/Picker.js

It does a simple equal check of selectedValue and picker items value to translate it to the native PickerIOS understands. https://github.com/facebook/react-native/blob/master/Libraries/Components/Picker/PickerIOS.ios.js#L53

Although the contents are same the object this.state.selectedValue and matching coWorkers[result] are different objects

You can generate some unique ids for each item in the array and use that to lookup the object.

Necessity

The PropType for value in the source code you linked is any, not string/integer – Sullage

@Sullage Do you mean not this ? github.com/facebook/react-native/blob/master/Libraries/… ? – Necessity

my response is over two years old. it's clearly been updated since and is no longer relevant. – Sullage

Answer 2

If someone else has this problem and the solutions above are not working, it might be because you don't have the selectedValue flag set to something:

// You can replace the null with an actual value in your array(check to see it's exact)
const [toLanguage, setToLanguage] = useState(null); 


selectedValue={toLanguage}

Burnard

Answer 3

Your itemValue.name is not matching your coWorkers[result]

Shortterm