Develop Reference

Ionic 4: Hardware Back Button Reloading Application

Working on a Project and stuck in an Issue:
Hardware Back Button Reloading Application (I am using Angular Router in this application).
My Code to Exit Application:
ionViewDidEnter(){
this.subscription = this.platform.backButton.subscribe(()=>{
navigator['app'].exitApp();
});
}
ionViewWillLeave(){
this.subscription.unsubscribe();
}
While same logic Working in other applications. but in this application its reloading the application not exiting it.
P.S: i have also tried it to put in platform.ready() but no luck.

With IONIC 4, there is new method subscribeWithPriority developed to handle race between soft & hard back button. Try modifying your code like below:
this.platform.backButton.subscribeWithPriority(1, () => {
navigator['app'].exitApp();
});
subscribeWithPriority() stops the propagation of the event after its execution and if we subscribe with high priority and execute our prefered navigation instead of default one then it is going to work as you want.
More reference docs for details:
https://github.com/ionic-team/ionic/commit/6a5aec8b5d76280ced5e8bb8fd9ea6fe75fe6795
https://medium.com/#aleksandarmitrev/ionic-hardware-back-button-nightmare-9f4af35cbfb0
UPDATES:
Try using this new version of exitApp cordova plugin. I haven't
tried myself but looks promising from popularity.
Also try to empty the page stack from Navcontroller or go to your home screen, seems like that's causing the reload for app with sidemenu's & tab pages... this.navCtrl.pop() / this._navCtrl.navigateBack('HomeScreen'), and then call exitApp.
NOTE: Tabs & SideMenu as those have its own routing module does create lot of complexity with app navigation.

Solved:
As Mention by #rtpHarry template of SideMenu / Tabs have History which leads application to Reload it self on root page. i was able to solve this by clearing History.
ionViewDidEnter(){
navigator['app'].clearHistory();
}
on Your Root Page just Clear your history and your Hardware Back Button will close the Application instead of Reloading it.

Do you have a sidemenu in your app? I'm just curious because this seems to be when I get this problem as well.
If you look in your inspector, you will see that window.history has a length of 1.
I don't see it in some of my apps, but the app that I have a side menu setup acts this way - on the homepage if you press back the screen goes white then it reloads the app.
Like I say, looking in the inspector shows that there is a history to step back to, which it is trying to do, and whatever that history step is, it just pushes it forward back to the homepage, which made me wonder if it was the sidemenu setting up its own control of the navigation system.
I've probably said some poorly worded terminology but as I haven't solved this myself I thought I would just let you know what I had found... hopefully it helps you move forward.
In my scenario, I wasn't even trying to do the exit on back code - I just noticed that the app would appear to "reboot" if I kept pressing back.

This explain the solution on Ionic 5 (and 4.6+ too I think).
private backButtonSub: Subscription;
ionViewDidEnter() {
this.backButtonSub = this.platform.backButton.subscribeWithPriority(
10000,
() => {
// do your stuff
}
);
}
ionViewWillLeave() {
this.backButtonSub.unsubscribe();
}
also keep
IonicModule.forRoot({
hardwareBackButton: true
}),
to true (default) in your app.module.ts
Sources:
https://www.damirscorner.com/blog/posts/20191122-CustomizingAndroidBackButtonInIonic4.html
The Doc

How to reload a page with a different XML template when orientation changes?

how to reload a page (with a new template) when the orientation of the device changes?
I want a different layout in landscape mode. This is in NativeScript, not Java.
the correct xml file is selected if i arrive at the page in landscape, but if i change orientation, nothing gets reloaded.
Note that this is not a question of refreshing the CSS, it is a different XML file needed.

NativeScript solution:
First you need to tie into the orientation event. You have a couple ways you can tie into that event.
The first and easiest method is to install the nativescript-orientation plugin, it ties into the event globally and then it will just automatically run your exported function on each of the current page called orientation, each time the orientation changes.
To Install:
tns plugin install nativescript-orientation
Open your app.js file and add at the top of the file;
require('nativescript-orientation');
Then by creating:
exports.orientation = function(args) {
if (args.landscaped) { /* do landscape stuff */ }
else { /* do port */
};
on any page you want to be notified that the orientation changed, it will be called on those pages that have that function and you can handle the event how you need to.
However, if you prefer to not use a plugin, you can directly tie into the orientation event yourself by doing:
var application = require('application');
exports.onNavigateTo = function() {
application.on(application.orientationChangedEvent,myOrientationFunction);
}
exports.onNavigateFrom = function() {
application.off(application.orientationChangedEvent, myOrientationFunction);
function myOrientationFunction(args) {
// We have an orientation event
}
However you must ask to be notified of the event when your page first open and you must remove your self from the notification when your page closes. This is a lot of extra code per page that the plugin above just handles for you. Please note when you are doing this yourself you also need to to add the NavigateTo/NavigatedFrom to the <Page> tag in your Declarative UI XML file, otherwise those functions won't be called.
Ok, now that you have the event which ever way you prefer; lets look at how we can make your idea work.
Now, you are asking to switch layouts each time the page changes; this is typically the worst thing to do; but I will answer it first and then give you the alternative method that I use to do complex layouts that work in both Portrait and Landscape modes pretty much automatically.
MyPage-Landscape.xml
<Page><StackLayout><Label text="Landscape"/></StackLayout></Page>
MyPage-Portrait.xml
<Page><StackLayout><Label text="Portrait"/></StackLayout></Page>
MyPage-Landscape.js
var commonPage = require("./MyPage.js");
var frame = require('ui/frame');
exports.orientation = function(args) {
if (args.landscape === false) {
frame.topmost().navigate('MyPage-Portrait');
}
};
// Tie all the common page code into this pages exports
for (var key in commonPage) {
if (commonPage.hasOwnProperty(key)) {
exports[key] = commonPage[key];
}
}
MyPage-Portrait.js
var commonPage = require("./MyPage.js");
var frame = require('ui/frame');
exports.orientation = function(args) {
if (args.landscape === true) {
frame.topmost().navigate('MyPage-Landscape');
}
};
// Tie all the common page code into this pages exports
for (var key in commonPage) {
if (commonPage.hasOwnProperty(key)) {
exports[key] = commonPage[key];
}
}
MyPage.js
exports.TapHandler = function() { /* Someone Tapped */ }
exports.someOtherLogic = function() { /* More logic */ }
exports.etc = function() { /* etc */ }
You put all your common page logic in the MyPage file; but you specifically navigate to the specific landscape or portrait page; and each of them are responsible to navigate to the other version if the page orientation changes.
Notes about the above solution:
You need to navigate to the proper version of the page from any other page; ie. if you are in Landscape mode; when you navigate to another page; you need to make sure you navigate to the Landscaped version of the page.
the NS-Orientation plugin does give you a handle helper function to find out the current orientation to make this easier.
Remember to make the MyPage.js have all the common code; you want to try and eliminate any custom code on a specific page version.
Their is a frame reload command you can use; however it totally clears the history; meaning you can't navigate backwards. i.e. Page1 -> Page2, frame.reloadPage() means that the back button will NOT go back to Page1. If this is acceptable; you can make the above system a lot simpler; rather than create separate xml & js files you just need a myPage.landscape.xml and myPage.portrait.xml and you need to on every orientation change just call the frame.reloadPage();
Now to me the above is some serious overkill for what is probably a simple change that you need done between pages. So I'm going to describe how I do it in my apps; which has some pretty complex screens but they look very nice and completely change functionality on a orientation change.
This is part of the reason the NativeScript-orientation plugin was written. On a page orientation change will automatically add / remove a "landscape" class name to the <Page> element in your XML. What this allows you to do in your CSS is:
.myLabel {
font-size: 12;
background-color: blue;
height: 20;
}
.landscape .myLabel {
font-size: 16;
background-color: green;
height: 40;
}
If you haven't figured out where I am going with this; this allows you to have custom CSS for the page while in landscape mode vs it being in portrait mode. In addition when you use the exports.orientation function in union with it also you can then run custom code depending on the orientation.
So in my case; On a phone my scroll list is a single scroll list of items going up down and is sized perfectly to the screen, and looks very sharp. When you switch to landscape mode; it hides the actionbar, adds a fab button, resizes the entire grid item to fit with the same proportions and switches scrolling modes to right-left. The majority of the entire look change is done in pure css; and the rest is done in the exports.orientation function which handles things like switching scroll direction.
Disclaimer: I am the author of the NativeScript-orientation plugin

In your activity:
#Override
public void onConfigurationChanged(Configuration newConfig) {
super.onConfigurationChanged(newConfig);
setContentView(R.layout.my_layout);
}
Make sure you have layout XML with same name for both orientations
res/layout/my_layout.xml
res/layout-land/my_layout.xml

With correct resource file names Android system automatically reloads your Activities/Fragments with proper resources.
You can catch and handle events manually by setting android:configChanges (but it is a rare case).
Check some documentation:
Handling Runtime Changes
Providing Resources

.focus() after reloading page with jQuery in phoneGap

I'm trying to solve an issue with a phonegap app for Android.
I have a function like this one on a dinamic page
$(objLid).change(
function (e){
//Save data for reload
_prototype.saveFormData();
//reload call
reloadPage();
//first attempt to have the focus on the right obj
$(objLid).focus();
}
);
That's how it work:
The button have type "select-one" after the user select one of the element i save all the previous item on text field, then i call the reload function that add other field on the page.
On iOs without the .focus() call i have no problem but on Android after the reload the application automatically makes a scroll at the top of the page. I've tried:
$mobile.silentscroll(Y) //with Y as a given Y position
But it work as the focus, after the reload Android makes a scroll at the top. The same with setTimout hoping for a delayed effect but unsuccessfully:
setTimeout(function() {
$(objLid).focus();
}, 1000 );
There's an hack to this annoying "scroll"?
Thanks

Android web view "back" button to load previously loaded div

I will try to explain this as clearly as possible. I have an android app using web view to basically load a webpage as my app. I have everything working great, however the back button seems to be an issue. I have set this page up all on one html page, it will load in a div when certain buttons are clicked to give the feel of a new page without actually having one. I basically want the back button (on the android tablet or smartphone) to load the previously loaded div, but I have no idea where to start with this. Here is what the content switching jquery looks like -
function contentSwitcher(settings){
var settings = {
contentClass : '.contentToLoad',
navigationId : '#sideMenu',
servFront : '#clickHomeHome'
};
//Hide all of the content except the first one on the nav
$(settings.contentClass).not(':first').hide();
$(settings.navigationId).find('li:first').addClass('active');
//onClick set the active state,
//hide the content panels and show the correct one
$(settings.navigationId).find('a').click(function(e){
var contentToShow = $(this).attr('href');
contentToShow = $(contentToShow);
//dissable normal link behaviour
e.preventDefault();
//set the proper active class for active state css
$(settings.navigationId).find('li').removeClass('active');
$(this).parent('li').addClass('active');
//hide the old content and show the new
$(settings.contentClass).hide();
contentToShow.show("slow");
});
}
contentSwitcher();
});
note: I've cropped out a bunch of it just to show how it works on a basic level.
Does anyone have any suggestions as to where to begin. I'd just like the back button function to be able to maybe check a started previous div name stored somewhere and load that.
thanks!

You can try using the History API. There are numerous tutorials on the web e.g. this one is quite good:
http://diveintohtml5.info/history.html
Basically this is how it works. When the user clicks the link for the div to show you push the state to the history stack.
history.pushState({<object with any information about state>}, pageTitle, newUrl);
This will push the state to the history stack meaning that when the user presses the back button on any modern browser like webkit it will take that state into consideration. When back action is taken it will then pop the state from the history stack. This action you have to listen to and handle in any way you see fit:
window.addEventListener("popstate", function(event) {
// event object contains the information from the pushed state
// do whatever needed to load the previous page here
});
The History API requires you to structure your code in a certain way for it to work well. For this I would recommend to use some existing framework that handle the back events for you e.g. Backbone.js. Hope this helps.

Android phonegap - click event is fired on the next screen

I'm using phonegap (cordova 2.8), and android 4.2.1,
I use as frame works: knockout, & jquery mobile.
The app is based on http://propertycross.com/jquery-mobile/
I get the following funny behavior:
when clicking on a button that moves to another screen #2,
if there is a button in #2 screen at the same location,
then it get clicked as well...
The only solution I found is to wrap the code that change the screen with setTimeout:
setTimeout(function() {
application.navigateTo(viewModel);
},600);
This solve the problem but slow down the app...
This is actually unfortunate since the phonegap is already too slow...
Thanks.

There are two things you can do:
1) e.stopPropagation(), e.preventDefault()
phopkins describes this here:
jQuery mobile tap event triggered for twice
I'll elaborate, as this was a major issue for me. This applies to any of the tap, click, vclick and probably other events.
Your event functions should have stopPropogation() and preventDefault() called, like so:
$('#selector').tap(function(e) {
//your code here
e.stopPropagation();
e.preventDefault();
});
This helps, however, I found that you could still get the "phantom" click.
2) Bind the event to the page, not the button.
That way it's not bound to the next page.
For example, for a page with id='myPage' and a button with id='myBtn':
$('#myPage').on('tap', '#myBtn', function(e) {
//your code here
e.stopPropagation();
e.preventDefault();
});