React Native how to call onPress event? - javascript

Hello there i am working on a beginner project of mine with React Native and right now i am not able to handle onPress event.
Render:
_renderRow(feed) {
return (
<TouchableHighlight onPress={() => this._pressRow()}>
<View style={styles.container}>
<Image
source={{uri: feed.thumbnail}}
style={styles.thumbnail}/>
<View style={styles.rightContainer}>
<Text style={styles.title}>{feed.title}</Text>
</View>
</View>
</TouchableHighlight>
);
}
And the onPress function
_pressRow() {
console.log('list item pressed')
}
Listview
<ListView
dataSource={this.state.dataSource}
renderRow={this._renderRow}
style={styles.listView}/>
This is what i get as an error.
undefined is not a function (evaluating _this3._pressRow())
EDIT
Thanks to #Cherniv. I forgot to bind this with the renderRow function, changed my code like that and worked as intended:
<ListView
dataSource={this.state.dataSource}
renderRow={this._renderRow.bind(this)}
style={styles.listView}/>

Is it not because you forgot the "_" before pressRow in method declaration ?

Related

undefined is not a function (near '...this.state.results.map...')

I'm new at react native.I have a problem that i've been dealing for a few days.I want to show my data with map.Can you guys show me where i did wrong?
(I think i made mistake in the results inside scrollview)
class Movie extends Component{
state= {
apiurl:'http://www.omdbapi.com/.............................',
s:'',
results: [],
selected:{}
}
searchFunc(s) {
this.setState({s: s})
axios(this.state.apiurl+ "&s="+s).then(response =>
this.setState({results: response.data.Search[0]}));
console.log(this.state.results)
}
render() {
return(
<View style={{flex:1,backgroundColor:'#356292'}}>
<View
style={styles.sectionContainer}>
<View style={styles.section}>
<TextInput style={styles.section2}
onChangeText = {(s) => this.searchFunc({s})}
value={this.state.s}
placeholder="Movies,Series.."
>
</TextInput>
<TouchableOpacity
style={{justifyContent: 'center', alignItems: 'center'}}
onPress={() => this.searchFunc()}>
<Image
source ={require('../img/seach.png')}
style={{width:width*0.05,height:height*0.03}}
>
</Image>
</TouchableOpacity>
</View>
</View>
<ScrollView style={styles.scroll}>
{this.state.results.map(results=>(
<View key={this.state.results.imdbID}
style={styles.scroll2}>
<Image source={{uri: this.state.results}}
style={{width:width*0.3, height:height*0.4}}>
</Image>
<Text style={styles.heading}>
{this.state.results.Title}
</Text>
</View>
))}
</ScrollView>
</View>
);
}
From the comments from your original post, i'm guessing response.data.Search[0] is also an array. If so your results state update is okay. Otherwise you should set the results state to response.data.Search.
Other problem I noticed in your code is in the map function, you are mapping the array with each item refering to the result variable, but in your jsx, you are trying to access the results state variable. It should be
<ScrollView style={styles.scroll}>
{
this.state.results.map(result => (
<View
key={result.imdbID}
style={styles.scroll2}
>
<Image
source={{uri: result.image}} // use correct key from result object
style={{width:width*0.3, height:height*0.4}}
/>
<Text style={styles.heading}>{result.Title}</Text>
</View>
))
}
</ScrollView>
Also in your Textinput onChangeText callback function, you dont have to pass that value as an object. You can change it to
<TextInput
style={styles.section2}
onChangeText={(s) => this.searchFunc(s)}
value={this.state.s}
placeholder="Movies,Series.."
/>
I quess you are supposed to pass Search to the state and not the Search[0], which is the object and not map, the reason map function is not working on it.
axios(this.state.apiurl+ "&s="+s).then(response =>
this.setState({results: response.data.Search}));
console.log(this.state.results)
Coincidently, I have created an app using same movie API, you can find it here: Github Repo, Movie App

React native, undefined is not an object (evalu....)

I'm creating a shopping cart in react native with redux but I'm getting an error
undefined is not an object (evaluating 'this.props.items.length')
I'm following a tutorial of react redux someone suggest me to follow that tutorial to make cart,
but I'm getting that error
can someone please tell me what's going on.., below is my code
class Cart extends Component {
render() {
let addedItems = this.props.items.length ? (
<FlatList
data={this.props.items}
key={(items) => items.id.toString()}
numColumns={2}
renderItem={({ item }) => (
<View>
<Image style={styles.image} source={item.image} />
<View style={styles.detailContainer}>
<Text style={styles.title}>{item.title}</Text>
<Text style={styles.subTitle} numberOfLines={1}>
Quantity: {item.quantity}
</Text>
<Text style={styles.price}>Rs {item.price}</Text>
</View>
<TouchableOpacity>
<View style={styles.buy}>
<Text>Remove</Text>
</View>
</TouchableOpacity>
</View>
)}
/>
) : (
<Text>Nothing</Text>
);
return (
<View>
<View>
<Text>You Have Ordered:</Text>
</View>
<View>{addedItems}</View>
</View>
);
}
}
const mapStateToProps = (state) => {
return {
items: state.addedItems,
};
};
try like this
let addedItems = this.props.items && this.props.items.length ? (

Get text from TextView and copy it to clipboard in react native

I want to copy value inside textview by clicking to icon. This is what I've done so far:
render() {
return (
<View style={{marginTop: 50, marginLeft: 50}}>
<View>
<Text>Логин:</Text>
<Text ref='myText'>45645546654</Text>
</View>
<TouchableOpacity onPress={() => Clipboard.setString(this.refs.myText.props.children)}>
<View>
<MaterialIcons
name='content-copy'
size={21}
/>
</View>
</TouchableOpacity>
</View>
);
}
Workspace: https://snack.expo.io/#jasurkurbanov/updated2
It is somewhat working on snack. But what when I am running it on my phone I am getting error.
Undefinied is not an object ('evaluating '_this.refs.myText.props.children')
You should defined your refs variable on constructor().
for example:
constructor() {
...
this.textViewRefs = React.createRef();
...
}
render() {
return (
...
<Text ref={this.textViewRefs}>45645546654</Text>
...
)
}
look this https://reactjs.org/docs/forwarding-refs.html for further information

React Native ScrollView disappears child component

I have this code:
<View style={{flex:1}}>
<ScrollView>
<View style={{flex:0.25,elevation:2,marginVertical:5}}>
<MoviesChild/>
</View>
<View style={{flex:0.75}}>
<FlatList
data={ListOfMovies}
renderItem={this.renderData.bind(this)}
keyExtractor={(x, i) => x.id}
extraData={this.state}
/>
</View>
</ScrollView>
</View>
The problem is, my FlatList's data appears but my child component MoviesChild disappears. Maybe Flatlist overlaps the child component. Could someone figure out where I'm doing a mistake please?
You should give style to ScrollView with flexGrow:1
I suggest you not to use FlatList inside a ScrollView, 'cause FlatList scroll itself. So, in order to achieve your objective, wrap your first View in a function and pass it to the ListHeaderComponent property of your FlatList, like this:
<View style={{flex:1}}>
<View style={{flex:0.75}}>
<FlatList
data={ListOfMovies}
renderItem={this.renderData.bind(this)}
keyExtractor={(x, i) => x.id}
extraData={this.state}
ListHeaderContainer={this.renderHeader}
/>
</View>
</View>
where
private renderHeader = () => {
return(
<View style={{flex:0.25,elevation:2,marginVertical:5}}>
<MoviesChild/>
</View>
)
}
I hope this can fix your issue!
You can find what I'm talking about on the official doc
Try this,
<View style={{flex:1}}>
<View style={{ flex:0.25,elevation:2,marginVertical:5 }}>
<MoviesChild/>
</View>
<FlatList
style={{flex:0.75}}
data={ListOfMovies}
renderItem={this.renderData.bind(this)}
keyExtractor={(x, i) => x.id}
extraData={this.state}
/>
</View>

React-Native: Cannot access state values or any methods declared from renderRow

I have a listview, whenever user clicks on an item, i want to do something with onPress (touchable highlight).
I tried defining function then calling them in onPress but they didnt work.
first i defined a function like this :
constructor(props) {
super(props);
this.state = {
dataSource: new ListView.DataSource({
rowHasChanged: (row1, row2) => row1 !== row2,
}),
loaded: false,
};
this._dosome = this._dosome.bind(this);
}
_dosome(dd){
console.log(dd);
}
Then :
render(){
if (!this.state.loaded) {
return this.renderLoadingView();
}
return (
<View style={{
flex: 1
}}>
<ListView
dataSource={this.state.dataSource}
renderRow={this.renderRow}
style={styles.listView}
/>
</View>
);
}
renderRow(data) {
var header = (
<View>
<View style={styles.rowContainer}>
<View style={styles.textContainer}>
<Text style={styles.title}>{data.nid}</Text>
<Text style={styles.description} numberOfLines={0}>{data.title}</Text>
</View>
</View>
<View style={styles.separator}></View>
</View>
);
///////////
var cid = [];
var content = [];
for(let x=0; x < Object.keys(data.course).length; x++){
cid[x] = data.course[x].course_id;
content.push(
<TouchableHighlight
underlayColor='#e3e0d7'
key={x}
onPress={ this._dosome } //// **** PROBLEM HERE ****
style={styles.child}
>
<Text style={styles.child}>
{data.course[x].title}
</Text>
</TouchableHighlight>
);
}
console.log(cid);
var clist = (
<View style={styles.rowContainer}>
{content}
</View>
);
////////////
return (
<Accordion
header={header}
content={clist}
easing="easeOutCubic"
/>
);
}
renderLoadingView() {
return (
<View style={styles.loading}>
<Text style={styles.loading}>
Loading Courses, please wait...
</Text>
</View>
);
}
}
But it didnt worked, error :
TypeError: Cannot read property '_dosome' of null(…)
I tried calling it onPress like this :
onPress={ this._dosome.bind(this) }
didn't help
onPress={ ()=> {this._dosome.bind(this)}}
didn't help
onPress={ console.log(this.state.loaded)}
even i cannot even access props defined in constructor. it don't know what is "this" !
I tried to define the function other way like this :
var _dosome = (dd) => {
console.log(dd);
};
I tried defining the _dosome before render, after render, inside render, inside renderRow, and after renderRow. all same results.
I did check lots of tutorials, lots of sample apps on rnplay, lots of threads in stackoverflow, lots of examples, but none of them worked for me.
any solutions/ideas?
Any help is highly appreciated. i'm struggling with this issue for 2 days now.
Thanks in Advance!
How to solve your problem
Change
<ListView
dataSource={this.state.dataSource}
renderRow={this.renderRow}
style={styles.listView}
/>
To
<ListView
dataSource={this.state.dataSource}
renderRow={data => this.renderRow(data)}
style={styles.listView}
/>
Or
<ListView
dataSource={this.state.dataSource}
renderRow={this.renderRow.bind(this)}
style={styles.listView}
/>
Why?
As you already know(since you are trying to solve the problem by using arrow function and bind), to call renderRow, the caller should be in the same context as the component itself.
But this connection is lost in renderRow={this.renderRow}, which created a new function(new context).

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