アプリ開発を高速化するためのライブリロード

So far, we’ve seen how easy it is to develop a cross-platform app that works everywhere. The development experience is pretty quick, but what if I told you there was a way to go faster?

We can use the Ionic CLI’s Live Reload functionality to boost our productivity when building Ionic apps. When active, Live Reload will reload the browser and/or WebView when changes in the app are detected.

Live Reload

Remember ionic serve? That was Live Reload working in the browser, allowing us to iterate quickly.

We can also use it when developing on iOS and Android devices. This is particularly useful when writing code that interacts with native plugins - we must run it on a device to verify that it works. Therefore, being able to quickly write, build, test, and deploy code is crucial to keeping up our development speed.

Let’s use Live Reload to implement photo deletion, the missing piece of our Photo Gallery feature. Select your platform of choice (iOS or Android) and connect a device to your computer. Next, run either command in a terminal, based on your chosen platform:

$ ionic cap run ios -l --external

$ ionic cap run android -l --external

The Live Reload server will start up, and the native IDE of choice will open if not opened already. Within the IDE, click the Play button to launch the app onto your device.

Deleting Photos

With Live Reload running and the app open on your device, let’s implement photo deletion functionality. Open tab2.page.html and add a new click handler to each <ion-img> element. When the app user taps on a photo in our gallery, we’ll display an Action Sheet dialog with the option to either delete the selected photo or cancel (close) the dialog.

<ion-col size="6" *ngFor="let photo of photoService.photos; index as position">
  <ion-img [src]="photo.webviewPath" (click)="showActionSheet(photo, position)"></ion-img>
</ion-col>

Over in tab2.page.ts, import Action Sheet and add it to the constructor:

import { ActionSheetController } from '@ionic/angular';

constructor(public photoService: PhotoService,
            public actionSheetController: ActionSheetController) {}

Add UserPhoto to the import statement.

import { PhotoService, UserPhoto } from '../services/photo.service';

Next, implement the showActionSheet() function. We add two options: Delete that calls PhotoService’s deletePicture() function (to be added next) and Cancel, which when given the role of “cancel” will automatically close the action sheet:

public async showActionSheet(photo: UserPhoto, position: number) {
  const actionSheet = await this.actionSheetController.create({
    header: 'Photos',
    buttons: [{
      text: 'Delete',
      role: 'destructive',
      icon: 'trash',
      handler: () => {
        this.photoService.deletePicture(photo, position);
      }
    }, {
      text: 'Cancel',
      icon: 'close',
      role: 'cancel',
      handler: () => {
        // Nothing to do, action sheet is automatically closed
        }
    }]
  });
  await actionSheet.present();
}

Save both of the files we just edited. The Photo Gallery app will reload automatically, and now when we tap on one of the photos in the gallery, the action sheet displays. Tapping “Delete” doesn’t do anything yet, so head back into your code editor.

In src/app/services/photo.service.ts, add the deletePicture() function:

public async deletePicture(photo: UserPhoto, position: number) {
  // Remove this photo from the Photos reference data array
  this.photos.splice(position, 1);

  // Update photos array cache by overwriting the existing photo array
  Preferences.set({
    key: this.PHOTO_STORAGE,
    value: JSON.stringify(this.photos)
  });

  // delete photo file from filesystem
  const filename = photo.filepath
                      .substr(photo.filepath.lastIndexOf('/') + 1);

  await Filesystem.deleteFile({
    path: filename,
    directory: Directory.Data
  });
}

The selected photo is removed from the Photos array first. Then, we use the Capacitor Preferences API to update the cached version of the Photos array. Finally, we delete the actual photo file itself using the Filesystem API.

Save this file, then tap on a photo again and choose the “Delete” option. This time, the photo is deleted! Implemented much faster using Live Reload. 💪

In the final portion of this tutorial, we’ll walk you through the basics of the Appflow product used to build and deploy your application to users' devices.