Ionic override all BACK button behaviour for specific controller

Question

I want to be able to override the BACK button on the navigation bar, and the hardware button.

I want this override to be for one specific controller, but not for the rest of the controllers.

• it must be cancelled when the user moves to another screen

(using ionic v1.0.0 uranium-unicorn)

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My reason is I have a list of items. Clicking on the list opens a details page, with 3 tabs. Each tab shares the same controller.

However, pressing BACK on any of those tabs must go back to the main list. That is how it works on native devices, so that is how I would like it to work on my hybrid app.

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Many solutions provided online seem to be for older beta versions, or for registration outside of controllers.

A common solution for working with the Android hardware button inside a controller is:

$ionicPlatform.registerBackButtonAction(function (event) {
  if($state.current.name=="home"){
    alert("button back");
  }
}, 100);

However this doesn't seem to work on the soft navigation bar button, and it works across all controllers, not just the one.

Answer 1

It is possible to override both buttons in your controller, without any changes the the HTML code.

To summarise:

• Soft navigation bar button - override $rootScope.$ionicGoBack()
• Hard Android button - use $ionicPlatform.registerBackButtonAction()

Detailed explanations below.

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The solution for overriding the soft navigation bar BACK button comes from understanding what Ionic does when that button is pressed.

From the Ionic docs for ion-nav-back-button, we already know that:

the button is automatically set to $ionicGoBack() on click/tap.

Searching the source code in ionic.bundle.js reveals how this is declared:

$rootScope.$ionicGoBack = function(backCount) {
    $ionicHistory.goBack(backCount);
};

Overriding this in your own controller is simple. Make sure you pass $rootScope into the controller and just modify the above code. It is a good idea to grab a pointer to the original function so you can restore it if required, or call into it when finished with your custom processing.

// grab pointer to original function
var oldSoftBack = $rootScope.$ionicGoBack;

// override default behaviour
$rootScope.$ionicGoBack = function() {
    // do something interesting here

    // uncomment below line to call old function when finished
    // oldSoftBack();
};

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The solution for overriding the Android hardware BACK button, for only one controller, comes from the return value of the registerBackButtonAction() function, which does the deregistration of the override.

Call that deregistration method in the $scope.$on('$destroy'... handler.

var doCustomBack= function() {
    // do something interesting here
};

// registerBackButtonAction() returns a function which can be used to deregister it
var deregisterHardBack= $ionicPlatform.registerBackButtonAction(
    doCustomBack, 101
);

$scope.$on('$destroy', function() {
    deregisterHardBack();
});

More details here:

• Ionic cancel hard BACK button override.

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A full solution would require the following:

• override soft navigation bar BACK button
• override Android hard BACK button
• scope would be a single controller
• default behaviour restored

The following code illustrates how this can be done:

// run this function when either hard or soft back button is pressed
var doCustomBack = function() {
    console.log("custom BACK");
};

// override soft back
// framework calls $rootScope.$ionicGoBack when soft back button is pressed
var oldSoftBack = $rootScope.$ionicGoBack;
$rootScope.$ionicGoBack = function() {
    doCustomBack();
};
var deregisterSoftBack = function() {
    $rootScope.$ionicGoBack = oldSoftBack;
};

// override hard back
// registerBackButtonAction() returns a function which can be used to deregister it
var deregisterHardBack = $ionicPlatform.registerBackButtonAction(
    doCustomBack, 101
);

// cancel custom back behaviour
$scope.$on('$destroy', function() {
    deregisterHardBack();
    deregisterSoftBack();
});

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This issue has been discussed on the Ionic forums & issues pages:

• How to handle a click on the generated back button?
• Custom back button onclick #438