195 lines
5.7 KiB
Markdown
195 lines
5.7 KiB
Markdown
## Class: DownloadItem
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> Control file downloads from remote sources.
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Process: [Main](../glossary.md#main-process)
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`DownloadItem` is an [EventEmitter][event-emitter] that represents a download item in Electron.
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It is used in `will-download` event of `Session` class, and allows users to
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control the download item.
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```javascript
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// In the main process.
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const { BrowserWindow } = require('electron')
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let win = new BrowserWindow()
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win.webContents.session.on('will-download', (event, item, webContents) => {
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// Set the save path, making Electron not to prompt a save dialog.
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item.setSavePath('/tmp/save.pdf')
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item.on('updated', (event, state) => {
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if (state === 'interrupted') {
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console.log('Download is interrupted but can be resumed')
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} else if (state === 'progressing') {
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if (item.isPaused()) {
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console.log('Download is paused')
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} else {
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console.log(`Received bytes: ${item.getReceivedBytes()}`)
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}
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}
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})
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item.once('done', (event, state) => {
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if (state === 'completed') {
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console.log('Download successfully')
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} else {
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console.log(`Download failed: ${state}`)
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}
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})
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})
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```
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### Instance Events
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#### Event: 'updated'
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Returns:
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* `event` Event
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* `state` String - Can be `progressing` or `interrupted`.
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Emitted when the download has been updated and is not done.
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The `state` can be one of following:
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* `progressing` - The download is in-progress.
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* `interrupted` - The download has interrupted and can be resumed.
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#### Event: 'done'
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Returns:
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* `event` Event
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* `state` String - Can be `completed`, `cancelled` or `interrupted`.
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Emitted when the download is in a terminal state. This includes a completed
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download, a cancelled download (via `downloadItem.cancel()`), and interrupted
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download that can't be resumed.
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The `state` can be one of following:
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* `completed` - The download completed successfully.
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* `cancelled` - The download has been cancelled.
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* `interrupted` - The download has interrupted and can not resume.
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### Instance Methods
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The `downloadItem` object has the following methods:
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#### `downloadItem.setSavePath(path)`
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* `path` String - Set the save file path of the download item.
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The API is only available in session's `will-download` callback function.
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If user doesn't set the save path via the API, Electron will use the original
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routine to determine the save path; this usually prompts a save dialog.
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#### `downloadItem.getSavePath()`
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Returns `String` - The save path of the download item. This will be either the path
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set via `downloadItem.setSavePath(path)` or the path selected from the shown
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save dialog.
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#### `downloadItem.setSaveDialogOptions(options)`
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* `options` SaveDialogOptions - Set the save file dialog options. This object has the same
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properties as the `options` parameter of [`dialog.showSaveDialog()`](dialog.md).
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This API allows the user to set custom options for the save dialog that opens
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for the download item by default.
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The API is only available in session's `will-download` callback function.
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#### `downloadItem.getSaveDialogOptions()`
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Returns `SaveDialogOptions` - Returns the object previously set by `downloadItem.setSaveDialogOptions(options)`.
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#### `downloadItem.pause()`
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Pauses the download.
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#### `downloadItem.isPaused()`
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Returns `Boolean` - Whether the download is paused.
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#### `downloadItem.resume()`
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Resumes the download that has been paused.
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**Note:** To enable resumable downloads the server you are downloading from must support range requests and provide both `Last-Modified` and `ETag` header values. Otherwise `resume()` will dismiss previously received bytes and restart the download from the beginning.
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#### `downloadItem.canResume()`
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Returns `Boolean` - Whether the download can resume.
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#### `downloadItem.cancel()`
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Cancels the download operation.
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#### `downloadItem.getURL()`
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Returns `String` - The origin URL where the item is downloaded from.
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#### `downloadItem.getMimeType()`
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Returns `String` - The files mime type.
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#### `downloadItem.hasUserGesture()`
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Returns `Boolean` - Whether the download has user gesture.
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#### `downloadItem.getFilename()`
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Returns `String` - The file name of the download item.
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**Note:** The file name is not always the same as the actual one saved in local
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disk. If user changes the file name in a prompted download saving dialog, the
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actual name of saved file will be different.
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#### `downloadItem.getTotalBytes()`
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Returns `Integer` - The total size in bytes of the download item.
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If the size is unknown, it returns 0.
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#### `downloadItem.getReceivedBytes()`
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Returns `Integer` - The received bytes of the download item.
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#### `downloadItem.getContentDisposition()`
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Returns `String` - The Content-Disposition field from the response
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header.
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#### `downloadItem.getState()`
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Returns `String` - The current state. Can be `progressing`, `completed`, `cancelled` or `interrupted`.
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**Note:** The following methods are useful specifically to resume a
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`cancelled` item when session is restarted.
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#### `downloadItem.getURLChain()`
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Returns `String[]` - The complete URL chain of the item including any redirects.
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#### `downloadItem.getLastModifiedTime()`
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Returns `String` - Last-Modified header value.
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#### `downloadItem.getETag()`
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Returns `String` - ETag header value.
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#### `downloadItem.getStartTime()`
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Returns `Double` - Number of seconds since the UNIX epoch when the download was
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started.
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### Instance Properties
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#### `downloadItem.savePath`
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A `String` property that determines the save file path of the download item.
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The property is only available in session's `will-download` callback function.
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If user doesn't set the save path via the property, Electron will use the original
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routine to determine the save path; this usually prompts a save dialog.
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[event-emitter]: https://nodejs.org/api/events.html#events_class_eventemitter
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