How to display a image selected from input type = file in reactJS

问题

I'm trying to display a image selected from my computer in my web app. I referred the following question which addresses the question i'm trying to fix.

How to display selected image without sending data to server?

I have my html part like this

 <div className="add_grp_image_div margin_bottom">
      <img src={img_upload} className="add_grp_image"/>
      <input type="file" className="filetype" id="group_image"/>
      <span className="small_font to_middle">Add group image</span>
      <img id="target"/>
 </div>

I want to display the selected image in

<img id="target"/>

How can i do this?

I referred FileReader docs as well.

https://developer.mozilla.org/en-US/docs/Web/API/FileReader

回答1:

Try this

<input type="file" onChange={this.onImageChange} className="filetype" id="group_image"/>

Add method to class

onImageChange = (event) => {
  if (event.target.files && event.target.files[0]) {
    let reader = new FileReader();
    reader.onload = (e) => {
      this.setState({image: e.target.result});
    };
    reader.readAsDataURL(event.target.files[0]);
  }
}

or you can use URL.createObjectURL

onImageChange = (event) => {
 if (event.target.files && event.target.files[0]) {
   this.setState({
     image: URL.createObjectURL(event.target.files[0])
   });
 }
}

And display image

<img id="target" src={this.state.image}/>

回答2:

hope it works for you

            <form onSubmit={form => submitForm(form)}>
              <input
                accept="image/*"
                onChange={onImageChange}
                className={classes.inputImage}
                id="contained-button-file"
                multiple
                name="image"
                type="file"
              />
              <label htmlFor="contained-button-file">
                <IconButton component="span">
                  <Avatar
                    src={mydata.imagePreview}
                    style={{
                      margin: "10px",
                      width: "200px",
                      height: "200px"
                    }}
                  />
                </IconButton>
              </label>
              <Button
                type="submit"
                variant="outlined"
                className={classes.button}
              >
                Default
              </Button>
            </form>

onImageChange

  const onImageChange = event => {
    if (event.target.files && event.target.files[0]) {
      let reader = new FileReader();
      let file = event.target.files[0];
      reader.onloadend = () => {
        setData({
          ...mydata,
          imagePreview: reader.result,
          file: file
        });
      };
      reader.readAsDataURL(file);
    }
  };

submitForm

  const submitForm = form => {
    form.preventDefault();
    const formData = new FormData();
    formData.append("image", mydata.file);
    // for (var pair of formData.entries()) {
    //   console.log(pair[1]);
    // }
    const config = {
      headers: {
        "content-type": "multipart/form-data"
      }
    };
    axios
      .post("api/profile/upload", formData, config)
      .then(response => {
        alert("The file is successfully uploaded");
      })
      .catch(error => {});
  };

来源：https://stackoverflow.com/questions/43992427/how-to-display-a-image-selected-from-input-type-file-in-reactjs

标签

reactjs

filereader

input-type-file