Develop Reference

React-Native Element changing size while scrolling

I'm trying to make a react-native scrollview with 3 (or more) elements where the element in the middle of the screen is always 1.75 times the normal element size, and while scrolling the size changes dynamically. Can I find when the element is in the center of screen if the size of the scrollview will be changing? Is it possible to do without some complicated mathematical approach?
I was trying putting conditions to all elements' styles but can't find a way to determine when the condition is met.
handleScroll(event) {
var x = event.nativeEvent.contentOffset.x;
var page = x / this.state.totalWidth;
this.setState({ position: page })
}
isElementFocused(start, stop) {
return (this.state.position >= start && this.state.position < stop);
}
Element:
<View style={styles.swipeBox,
{
backgroundColor: this.isElementFocused(1, 2) ? this.getColor(1) : colors.primary,
width: this.isElementFocused(1, 2) ? this.getWidth(1) : this.state.baseWidth,
height: this.isElementFocused(1, 2) ? this.getHeight(1) : this.state.baseHeight,
}}>
<Text>test</Text>
</View>

I think you want to use smoothScrollToPosition()
please visit https://www.programcreek.com/java-api-examples/?class=android.support.v7.widget.RecyclerView&method=smoothScrollToPosition

Fastest Way To Display 100 or more images in Flutter

The purpose of this question is to find the best way to display a lot of images (20 or more) from the gallery.
I need to display all the photos on the on the device. As you can see there could be a lot of images to be displayed, and when I try to display them all using different Image.file() widget, My phone (LG G2) gets slow and then the app completely crashes.
I think the Problem Is that I am Loading a lot of 4K Images (More Than 100) on a 5 years old Device. The Images actually displayed on the Screen at the same time are actually around 15, but I need to have something like a gallery, so all the images in a GridView.
So, I don't think it's the best option, maybe there is a function to downscale the image to like 100x100 px. But looking online I couldn't find anything. So, Is there a better way?
I get all the Image Paths and their folder using a Platform Channel to Android.
I get them all in a list like this:
[["Camera", "storage/emulated/0/downloads/1.png"], etc]
This is The UI I got: (Sorry For the Awful design)
There Are three Main components on the Screen, The IconButton With The Two Arrows:
The DropDownMenu and The GridView.
The IconButton requeries all the paths from android. in the List as stated above.
The DropDown Menu has a function on onChanged which creates all the Cards in the List used by gridView.
This is The Funciton:
void _onChanged(String value) {
setState(() {
_currFolder = value;
_photoCards = calculatePhotoCards();
});
}
And the calculatePhotoCards is this:
List<Widget> calculatePhotoCards() {
List<Widget> list = new List();
for (int v = 0; v < _foldersAndPaths.length; v++) {
if (_foldersAndPaths[v][0] == _currFolder) {
list.add(Card(
color: Colors.white,
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.all(Radius.circular(20.0))),
child: Padding(
padding: const EdgeInsets.all(8.0),
child: new ClipRRect(
borderRadius: new BorderRadius.circular(8.0),
child: Image.file(
File(_foldersAndPaths[v][1]),
fit: BoxFit.cover,
),
),
),
));
}
}
print(list);
return list;
}
Where _foldersAndPaths is the List containing all the paths which their respective folders (as stated above), while _currFolder is the Selected Folder in DropDownMenu.

You need to add cacheWidth and cacheHeight
example:
Image.network(
shop.shopPic,
width: 46,
height: 46,
cacheWidth: 46,
cacheHeight: 46,
)

I decided to implement this to see if it was something to do with image sizing etc, as there have been a few questions about that in the past for remote images.
When I implemented it, I ran into the exact same problem as you. I thought that flutter did caching of images scaled to a reasonable size but that doesn't seem to be the case. It's actually loading up each image into memory, which is why you're getting a crash. It doesn't take that many images to run out of memory as by the time they're decoded into pixels they're pretty huge.
Here and here are bugs about this (I raised one myself) against flutter.
So unfortunately, I don't think there's a pure flutter way of doing this at the moment. There is a image package on pub that can scale down images but it does it directly in dart code so isn't all that performant.
Until those bugs have been fixed, you may have to look for an android-specific (and iOS-specific if you're interested in that) solution to this. That would entail using the android thumbnail creator to create a bitmap, then either saving that bitmap and passing it's URL back to flutter, or passing the bitmap's bytes directly.
Sorry I don't have a better answer than that!

I'm using CachedNetworkImage and I had an issue with loading multiple Images and the app got to over 3GB ram because of it the solution was
CachedNetworkImage(
height: height,
width: width,
memCacheHeight: height, //add this line
memCacheWidth: width, //add this line
imageUrl: imageUrl,
),
It reduced the memory usage from3GB to 60MB

React Native images won't display on certain mobile devices

I've been developing a mobile app using React Native and deploying it onto a Samsung Galaxy S6 Edge for testing purposes via Expo. So far, everything has worked fine and all of the images I'm using have displayed correctly.
However, when I've tried to deploy it onto other devices, certain images have failed to display. On the Huawei MediaPad, the header image (encased in an <Image> tag) fails to display and on the Samsung Galaxy S8 and the OnePlus 6, the background image (encased in an <ImageBackground> tag) fails to display.
I've attempted running a compiled APK file of the app, believing that these issues could be related to streaming the images over Wi-Fi, but to no avail. Interestingly though, the background image displayed fine across all devices until I swapped it out for a new image (as the predecessor was merely a placeholder). Both images are 4K (3840 x 2160), with the only difference being the storage size of the image. As a debugging measure, I compressed the new image in Photoshop with the strongest setting but, again, to no avail.
Below is the code I am using to render the two Images (not a complete paste of course, but I'm happy to do so on request):
<ImageBackground
source={require('./../../assets/images/bg_portrait_dots.png')}
style={{width: '100%', height: '100%', position: 'absolute'}}
>
<View style={styles.parentView}>
<View style={styles.elementSpacer}>
<Image
source={require('./../../assets/images/iview_learning_logo.png')}
style={styles.headerImage}
/>
</View>
Below are the Stylesheet arguments which control the elements listed above:
parentView: {
flex: 1,
flexDirection: 'column',
padding: 30,
justifyContent: 'center',
},
headerImage: {
width: null,
resizeMode: 'contain',
height: 120,
position: 'relative',
},
elementSpacer: {
flex: 1,
},

QML elements over device's status bar

I am facing a problem when the device's keyboard is shown. The elements go over the device's status bar as in the images.
I have already tried to use the Flickable type but it does not work. Every time the keyboard appears, it push the app elements over the status bar.
PS: The problem occurs in both Android and iOS.
Here is the code:
import QtQuick 2.4
import QtQuick.Window 2.2
import QtQuick.Controls 1.3
Window {
visible: true
property int larguraTela: 360
property int alturaTela: 640
width: larguraTela
height: alturaTela
maximumWidth: larguraTela
maximumHeight: alturaTela
minimumWidth: larguraTela
minimumHeight: alturaTela
title: "OverStatusBar"
Rectangle{
id: retangulo1
width: parent.width
height: parent.height * 0.5
anchors.top: parent.top
color: "grey"
}
Rectangle{
id: retangulo2
width: parent.width
height: parent.height * 0.5
anchors.top: retangulo1.bottom
color: "lightgrey"
TextField {
id: campoTexto
width: parent.width * 0.7
height: parent.height * 0.15
anchors.centerIn: parent
inputMethodHints: Qt.ImhDigitsOnly
}
}
}

This behavior was accepted as bug by Qt. If someone would like to keep up with, here is the link
https://bugreports.qt.io/browse/QTBUG-50200

On Android: You need to add android:windowSoftInputMode="adjustResize" in the end of activity tag, so it will look something like this:
<activity ... android:windowSoftInputMode="adjustResize">

jQuery wScratchPad: Responsive Design?

I have added the wScratchPad to a website project. And it's working.
But the project is based on responsive design. That means the size of all elements adapt to the screen size, so it's optimized for mobile devices too.
The situation is that the size of the scratch-area remains the same, no matter how small you make the browser-window.
<div id="wScratchPad"></div>
<script type="text/javascript">
var scratch = function(e, percent){
if ( percent > 50 ) {
sp.wScratchPad('clear');
}
}
var sp = $("#wScratchPad").wScratchPad({
width : 363,
height : 117,
realtimePercent : true,
scratchDown: scratch,
scratchMove: scratch,
cursor:'./cursors/coin.png',
scratchUp: scratch,
image: './images/1.png',
image2: './images/2.png'
});
</script>
The "width" and "height" are needed to calculate the overlaying canvas and the pixels for uncovering the background-image.
Is there any way to let the scratch area size adapt to the window-size?

One solution you could try would be to set the scratchpad's dimensions to be a percentage of the dimensions of the browser viewport, using document.documentElement.clientWidth/clientHeight. For example:
var sp = $("#wScratchPad").wScratchPad({
width : document.documentElement.clientWidth / 4,
height : document.documentElement.clientHeight / 4,
...
});