Ionic 4-在平台硬件后退按钮android上关闭或关闭Modal [英] Ionic 4 - Dismiss or close Modal on platform hardware back button android

问题描述

在ionic 4中，按下硬件后退按钮时，我要关闭或消除将出现的任何模式. 我使用了下面给出的代码，即使前面的模态被取消，条件"if(modal){modal.dismiss();}"也总是得到满足

In ionic 4, on hardware back button press I want to close or dismiss any modal that will be present. I have used the below given code, here the condition "if(modal) { modal.dismiss(); }" always get satisfied even if previous modal are dismissed

constructor(private platform: Platform, private modalCtrl: ModalController) {
this.initializeapp();
}
initializeapp() {
this.platform.registerBackButtonAction(1, async () => {
    const modal = await this.modalCtrl.getTop();
    if (modal) {
        modal.dismiss();
    }
});
}

推荐答案

进行了一些挖掘，并且Ionic注册了一个自定义事件ionBackButton来处理对硬件后退按钮的按下:

Did some digging around and Ionic registers a custom event ionBackButton for handling the hardware back button press:

• https ://github.com/ionic-team/ionic/blob/master/core/src/utils/hardware-back-button.ts#L20

并且管理Ionic中所有叠加的叠加代码通过消除最上面的叠加来处理此ionBackButton事件:

And the overlay code that manages all overlays in Ionic handles this ionBackButton event by dismissing the topmost overlay:

• https://github .com/ionic-team/ionic/blob/master/core/src/utils/overlays.ts#L66

那么您的代码想要实现什么?

So what is your code trying to achieve?

似乎只有在backdropDismiss也设置为true时，它才会这样做:

It seems that it only does this when backdropDismiss is also set to true:

if (lastOverlay && lastOverlay.backdropDismiss) {

我认为这意味着它被分类为可选/低级叠加层，而不是模拟模态.

Which I assume means that it's classed as an optional/low-grade overlay, rather than simulating a modal.

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