如何使FileReader与Angular2一起使用？

Question

如何使FileReader与Angular2一起使用 !!

使用Angular2和Typescript 从客户端读取文件时,

我尝试以这种方式使用FileReader:

var fileReader = new FileReader();
fileReader.onload = function(e) {
    console.log("run fileReader.onload");
   //  ......
}

但它根本不起作用,这个'fileReader.onload'函数永远不会被调用.

真的需要一个阅读文件的解决方案,请帮忙.谢谢

从在线IDE检查:

预览:https: //angular2-butaixianran.c9.io/src/index.html

编辑:https: //ide.c9.io/butaixianran/angular2

Answer 1

首先,您必须在模板中的输入表单上指定change事件的目标:

@View({
  template:`
    <div>
      Select file:
      <input type="file" (change)="changeListener($event)">
    </div>
  `
})

如你所见,我将一个changeListener()方法绑定到(change)事件.我的课程实施:

  changeListener($event) : void {
    this.readThis($event.target);
  }

  readThis(inputValue: any) : void {
    var file:File = inputValue.files[0]; 
    var myReader:FileReader = new FileReader();

    myReader.onloadend = function(e){
      // you can perform an action with readed data here
      console.log(myReader.result);
    }

    myReader.readAsText(file);
  }

监听器将文件从事件传递给readThis方法.阅读这已经实现了它自己FileReader.您也可以在函数中定义组件中的FileReader.

Answer 2

来自@ haz111的回答已经有效,但是如果你想让文件阅读器成为一个可重复使用的组件,你可以使用这个或更好的:改进:

inputfilereader.ts

import {Component, ElementRef, EventEmitter} from 'angular2/angular2';

@Component({
    selector: 'filereader',
    templateUrl: './commons/inputfilereader/filereader.html',
    styleUrls: ['./commons/inputfilereader/filereader.css'],
    providers: [ElementRef],
    events : ['complete']
})

export class InputFileReader {
    complete :EventEmitter = new EventEmitter();

    constructor(public elementRef: ElementRef) {
    }

    resultSet:any; // dont need it 

    changeListener($event: any) {
        var self = this;
        var file:File = $event.target.files[0];
        var myReader:FileReader = new FileReader();
        myReader.readAsText(file);
        var resultSet = [];
        myReader.onloadend = function(e){
            // you can perform an action with data read here
            // as an example i am just splitting strings by spaces
            var columns = myReader.result.split(/\r\n|\r|\n/g);

            for (var i = 0; i < columns.length; i++) {
                resultSet.push(columns[i].split(' '));
            }

            self.resultSet=resultSet; // probably dont need to do this atall
            self.complete.next(self.resultSet); // pass along the data which would be used by the parent component
        };
    }
}

filereader.html

<input type="file" (change)="changeListener($event)" />

用于其他文件

另一个文件让我们说dfs.ts

import {Component, ElementRef} from 'angular2/angular2';
import {InputFileReader} from '../../commons/inputfilereader/inputfilereader';

@Component({
    selector: 'dfs',
    templateUrl: './components/dfs/dfs.html',
    styleUrls: ['./components/dfs/dfs.css'],
    providers: [ElementRef],
    directives:[InputFileReader]
})

export class DfsCmp {
    constructor(public eleRef :ElementRef) {}

    callSomeFunc(data):void {
        console.log("I am being called with ", data);
    }
}

dfs.html

<filereader (complete)="callSomeFunc($event)"></filereader>