Background
In my React Native application I am passing a component which renders a button with an onPress function. When this button is pressed it should take the user to a web page to view some information. Instead of the button working when it is clicked it is firing off and taking the user to the web page without being clicked. I am unsure why this is happening and would like some insight.
Example
This is where the button originates from.
Button Component
class Button extends Component {
constructor(props) {
super(props);
}
render() {
return (
<TouchableOpacity onPress={this.props.onPress()} style={styles.cardButtonWrap}>
<Text style={styles.cardButton}>Button</Text>
</TouchableOpacity>
);
}
}
AlbumDetail
This is where the Button component is called.
class AlbumDetail extends Component {
constructor(props) {
super(props);
}
render() {
return(
<Button onPress={() => Linking.openURL(this.props.album.url)} />
);
}
}
You are calling the function inside of onPress. Use this code instead:
class Button extends Component {
constructor(props) {
super(props);
}
render() {
return (
<TouchableOpacity onPress={this.props.onPress} style={styles.cardButtonWrap}>
<Text style={styles.cardButton}>Button</Text>
</TouchableOpacity>
);
}
}
Related
I'm trying do show a modal screen with a button, when i press the button the modal will appears. The variable that is responsable for it is modalVisible and its a variable state. But if my button is not in the same class of my screen Profile i'm not able to change the variable, at last i dont know a way to do:
class Carrousel extends React.Component {
render () {
return (
<Button
title= 'press me to show up'
onPress= {() => this.props.visible = true}
/>
);
}
}
export default class Profile extends React.Component {
constructor(props) {
super(props);
this.state = {
modalVisible: true,
};
}
render() {
return (
<View>
<Modal
visible = {this.state.modalVisible}>
</Modal>
<Carrousel visible = {this.state.modalVisible}/>
</View>
);
}
}
Is there an way to change this variable modalVisible in another class? Or is there another way to i show the modal with a button in another class?
*The carrousel class is another file Carrousel.js.
You have to set a function as a prop that changes the state on the Parent Component. I haven't tried but it should be something like this:
class Carrousel extends React.Component {
render () {
return (
<Button
title= 'press me to show up'
onPress= {() => this.props.setVisible()}
/>
);
}
}
export default class Profile extends React.Component {
constructor(props) {
super(props);
this.state = {
modalVisible: false,
};
this.setVisible = this.setVisible.bind(this);
}
setVisible() {
this.setState({
modalVisible: true,
})
}
render() {
return (
<View>
<Modal
visible = {this.state.modalVisible}>
</Modal>
<Carrousel setVisible={this.setVisible}/>
</View>
);
}
}
So, I've just figured out today that only changing state in a React Native app triggers a re-render of the component. I'm changing state, but I'm doing it from a child component, and it seems to getting stuck in some loop, and () => { this.setState({current_time:'whatever'}) doesn't seem to do anything at all. How can I change my App.js's current_time in state from TimePicker.js?
App.js
export default class App extends React.Component {
constructor(props) {
super(props);
this.state = {
current_time:'initial time, unchanged in state',
};
}
render() {
let s = styles;
return (
<View style={s.contain}>
<TimePicker />
<ShowTime current_time={this.state.current_time} />
</View>
);
}
}
TimePicker.js
class TimePicker extends Component {
constructor(props){
super(props);
}
render(){
let s = styles;
return(
<TouchableOpacity>
<View style={s.contain} onPress={
/*
set this.state.current_time in parent to the actual current time
this.setState({current_time:'changed'}) seems to cause an infinite loop?
() => { this.setState({current_time:'changed'}) } doesn't seem to do anything
*/
}>
<Text>I will change the time in state.</Text>
</View>
</TouchableOpacity>
)
}
};
ShowTime.js
class ShowTime extends Component {
constructor(props){
super(props);
}
render(){
let s = styles;
return(
<View style={s.contain}>
<Text>{this.props.current_time}</Text>
</View>
)
}
};
Create a function in App.js and pass it as prop to TimePicker Component and the purpose of this function should be to setState . e.g
App.js
export default class App extends React.Component {
constructor(props) {
super(props);
this.state = {
current_time:'initial time, unchanged in state',
};
}
currentTimeHandler = (newCurrentTime) => {
this.setState({current_time: newCurrentTime});
}
render() {
let s = styles;
return (
<View style={s.contain}>
<TimePicker getTime={ this.currentTimeHandler }/>
<ShowTime current_time={this.state.current_time} />
</View>
);
}
}
TimePicker.js
class TimePicker extends Component {
constructor(props){
super(props);
}
render(){
let s = styles;
return(
<TouchableOpacity onPress={() => this.props.getTime('changes will be passed here')}>
<View style={s.contain} >
<Text>I will change the time in state.</Text>
</View>
</TouchableOpacity>
)
}
};
The reason is the setState only set the existing states locally in the js file. that would be your Timepicker.
In your case TimePicker is a child(or sub branch) of App (Your app stores your state, by your current build, and will never be changed by a child). You will need create two functions one in TimePicker and another App. TimePicker will handle the data and send it, via prop, the App will receive the prop and then trigger another function to setState.
Pass data from child to parent in React
This is the best one i can find.
Best read this as well:
https://reactjs.org/docs/react-component.html
It does say, setState only affect to local states, your state you want to set is not local.
export default class TopMiddleLoadingView extends React.Component{
size = 66;
constructor(props) {
super(props);
this.state = {
fill : 99,
timeLeft : props.timeLeft
}
}
onPress(){
this.setState = {
...this.state, fill:10
}
}
componentWillUpdate(nextProps, nextState) {
alert("componentWillUpdate");
}
render(){
alert("render")
return(
<View style={{width:this.size, height:this.size}}>
<View style={[styles.absoluteCenter,{zIndex:999}]}>
<Thumbnail source={Images.seaImg}></Thumbnail>
</View>
<Text>{this.state.fill}</Text>
<Button
style={{width:50,height:50,backgroundColor:"red",position:"absolute",zIndex:999}}
onPress={this.onPress}
></Button>
</View>
);
}
}
on button press, onPress function is clicked, and change the state of the component, but the render function is not calling.
I am very new to react native. Any idea?
You aren't changing the state either let alone re render. And if you want to re render then you should change state using setState() method. Also, you need to refresh you javascript this knowledge
export default class TopMiddleLoadingView extends React.Component{
size = 66;
constructor(props) {
super(props);
this.state = {
fill : 99,
timeLeft : props.timeLeft
}
}
onPress = () => {
this.setState({fill:10})
}
componentWillUpdate(nextProps, nextState) {
alert("componentWillUpdate");
}
render(){
alert("render")
return(
<View style={{width:this.size, height:this.size}}>
<View style={[styles.absoluteCenter,{zIndex:999}]}>
<Thumbnail source={Images.seaImg}></Thumbnail>
</View>
<Text>{this.state.fill}</Text>
<Button
style={{width:50,height:50,backgroundColor:"red",position:"absolute",zIndex:999}}
onPress={this.onPress}
></Button>
</View>
);
}
}
Render method is called whenever there is change in state of that component. You should use this.setState({...this.state, fill:10} for updating state of the component. This must cause render function to fire again, if there is not any other logic written inside shouldComponentUpdate() for conditional rendering.
Hope this helps. Also check out,
What the difference of this.state and this.setstate in ReactJS?
Let's assume I have this custom component:
export default class Button extends Component {
render(){
return(
<TouchOpacity>
<Text> Button </Text>
</TouchOpacity>
)
}
}
And I use it in a parent component like this :
export default class MainPage extends Component {
render(){
return(
<Button onPress={ this.doSomething }></Button>
)
}
}
For some reason (unknown to me at least) this onPress even won't happen.
I'm pretty new to react-native btw. I believe I must find a way to enable this kind of event handling.
Is it possible to get a small example how to achieve that based on my examples above ?
So, just found out how to handle this.
export default class Button extends Component {
constructor(props){
super(props)
}
render(){
return(
<TouchableOpacity
onPress={this.props.onPress}
>
<Text> Button </Text>
</TouchableOpacity>
)
}
}
and
export default class MainPage extends Component {
render(){
return(
<Button onPress={ this.doSomething }></Button>
)
}
}
Long story short: since the onPress I'm passing is a prop in the MainPage, I'm passing it a function (this.doSomething) which later on is activated in Button's onPress.
Nick's answer is right.Along with that if you want to call separate function for both child and parent component then you can use onPressOut. This will help to manage state of componant
export default class Button extends Component {
constructor(props){
super(props)
}
onClickListen = () => {
if (this.state.isSelected === false) {
this.setState({isSelected:true});
isSelectedPass=true;
}
else {
this.setState({isSelected:false});
isSelectedPass=false;
}
}
render(){
return(
<TouchableOpacity
onPress={this.props.onPress} onPressOut={this.onClickListen}
>
<Text> Button </Text>
</TouchableOpacity>
)
}
}
export default class MainPage extends Component {
render(){
return(
<Button onPress={ ()=>this.doSomething }></Button>
)
}
}
My modal displays an input form. I want to import contents of my Modal from another js file for keeping the main code shorter. I am actually able to import contents of my Modal from another class file by calling component's class name as jsx tag, but in this case I cannot pass state variables of main component to inner component of the modal or vice versa. And, I don't know if it is possible to receive data from the modal in this case. I know that I could use navigator with passProps, but I want to use just a modal for this purpose. For instance:
this is main Component:
class Main extends React.Component {
constructor(props){
super(props);
this._showAddNewModal = this._showAddNewModal.bind(this);
this.state = {
addNewShow: false,
mytext: '' // this should be updated through Modal.
}
}
render(){
return (
<TouchableHighlight onPress={() => {this._showAddNewModal();}}>
<Text> Show my modal </Text>
</TouchableHighlight>
<Modal visible={this.state.addNewShow}>
<MyModalContents />
</Modal>
);
}
_showAddNewModal(){
this.setState({addNewShow: true});
}
}
this is the component to be displayed in the modal:
class MyModalContents extends React.Component { // extends Modal?
constructor(props){
super(props);
this.state = {mytext: ''}
}
render(){
<View>
<TextInput onChangeText={(text) => this.setState({mytext: text})} />
</View>
}
}
I can't even close the modal because the state of 'addNewShow' is not accessible from MyModalContents. Any help will be appreciated.
You can pass props to a child component by cloning it with React.cloneElement. Here's an example of how you could use it with your modal:
class Main extends React.Component {
constructor(props){
super(props);
this.state = {
mytext: '' // this should be updated through Modal.
}
}
_showAddNewModal(){
this.refs.modal.show();
}
render(){
return <View>
<TouchableHighlight onPress={this._showAddNewModal}>
<Text> Show my modal </Text>
</TouchableHighlight>
<Modal parent={this} ref="modal">
<MyModalContents />
</Modal>
</View>
}
}
Modal
class Modal extends React.Component {
constructor(props){
super(props);
this.state = {
visible: false,
}
}
show() {
this.setState({visible: true});
}
close(){
this.setState({visible: false});
}
render(){
return <View style={{opacity: this.state.visible ? 1 : 0}} pointerEvents={this.state.visible ? 'auto' : 'none'}>
{/* can pass props with second argument */}
{React.cloneElement(this.props.children, {
parent: this.props.parent,
modal: this
})}
</View>
}
}
MyModalContents
class MyModalContents extends React.Component {
constructor(props){
super(props);
}
_updateModalState() {
const self = this;
// will update the "Main" component state as props are passed through modal
this.props.parent.setState({myText: 'Updated Text!'}, () => {
self.props.modal.close();
});
}
render(){
return <View>
<TouchableHighlight onPress={this._updateModalState}>
<Text> Update Modal State </Text>
</TouchableHighlight>
</View>
}
}