如何在Angular的本地存储中存储FILE(2及更高版本) [英] How to store a FILE in Local Storage in Angular (2 and up)
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问题描述
我只想将图像或pdf或任何类型的文件存储在本地存储中.
那么,有没有办法在LocalStorage中存储文件?
I want to just store the image or pdf or any type of file in local storage.
So, is there a way to store a file in LocalStorage?
推荐答案
这是一项独立的服务,可在Angular 6/7/8上运行.
它下载,存储和检索本地存储中的文件.
Here is a standalone service which works on Angular 6/7/8.
It downloads, stores and retrieves a file in local storage.
import { Injectable } from '@angular/core';
import { Observable } from 'rxjs';
import { HttpClient } from '@angular/common/http';
import { map, flatMap } from 'rxjs/operators';
@Injectable({
providedIn: 'root'
})
export class OcFileStorageService {
//#region Lifecycle methods
constructor(private httpSvc: HttpClient) { }
//#endregion Lifecycle methods
//#region Exposed methods
/**
* Tries to retrieve base64 file from local storage.
* If doesn't exist, downloads stores and retrieves the file again.
* @param key Key to search in storage
* @param urlIfNotExist Url which will be downloaded if key wasn't found
* @returns Observable of base64 data url string with the file inside
*/
public getStoredFile(key: string, urlIfNotExist: string): Observable<string> {
const storedFile = this.getFromStorage(key);
if (storedFile) {
return this.objectToObserver<string>(storedFile);
} else {
return this.downloadDataAsBase64(urlIfNotExist).pipe(
map((b64Result: string) => {
this.saveToStorage(key, b64Result);
return b64Result;
})
);
}
}
//#region Exposed methods
//#region Storage methods
private saveToStorage(key: string, b64Result: string) {
localStorage.setItem(key, b64Result);
}
private getFromStorage(key: string) {
return localStorage.getItem(key);
}
//#endregion Storage methods
//#region Downloader methods
private downloadAsBlob(url: string) {
return this.httpSvc.get(url, { responseType: 'blob' });
}
private downloadDataAsBase64(url: string): Observable<string> {
return this.downloadAsBlob(url).pipe(
flatMap(blob => {
return this.blobToBase64(blob).pipe(
map((b64Result: string) => {
return b64Result;
})
);
})
);
}
//#endregion Downloader methods
//#region Util methods
private blobToBase64(blob: Blob): Observable<{}> {
const fileReader = new FileReader();
const observable = new Observable(observer => {
fileReader.onloadend = () => {
observer.next(fileReader.result);
observer.complete();
};
});
fileReader.readAsDataURL(blob);
return observable;
}
private objectToObserver<T>(storedFile: T): Observable<T> {
return new Observable<T>(observer => {
observer.next(storedFile);
observer.complete();
});
}
//#region Util methods
}
用法非常简单:
constructor(private ocFileStorageSvc: OcFileStorageService) {}
ngOnInit() {
this.ocFileStorageSvc
.getStoredFile('quokka', 'https://pbs.twimg.com/media/DR15b9eWAAEn7eo.jpg')
.subscribe((base64Data: string) => {
this.quokkaImageData = base64Data;
});
}
此处是一个演示,以备不时之需.
And here is a demo just in case you need.
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