带有异常处理和异步任务的版本:

AsyncTask<URL, Void, Boolean> asyncTask = new AsyncTask<URL, Void, Boolean>() {
    public Bitmap mIcon_val;
    public IOException error;

    @Override
    protected Boolean doInBackground(URL... params) {
        try {
            mIcon_val = BitmapFactory.decodeStream(params[0].openConnection().getInputStream());
        } catch (IOException e) {
            this.error = e;
            return false;
        }
        return true;
    }

    @Override
    protected void onPostExecute(Boolean success) {
        super.onPostExecute(success);
        if (success) {
            image.setImageBitmap(mIcon_val);
        } else {
            image.setImageBitmap(defaultImage);
        }
    }
};
try {
    URL url = new URL(url);
    asyncTask.execute(url);
} catch (MalformedURLException e) {
    e.printStackTrace();
}

如果你是在点击按钮的基础上加载图像，上面接受的答案是很棒的，但是如果你是在一个新的活动中做这件事，它会冻结UI一到两秒钟。环顾四周，我发现一个简单的asynctask消除了这个问题。

要使用asynctask，在activity的末尾添加这个类:

private class DownloadImageTask extends AsyncTask<String, Void, Bitmap> {
    ImageView bmImage;

    public DownloadImageTask(ImageView bmImage) {
        this.bmImage = bmImage;
    }

    protected Bitmap doInBackground(String... urls) {
        String urldisplay = urls[0];
        Bitmap mIcon11 = null;
        try {
            InputStream in = new java.net.URL(urldisplay).openStream();
            mIcon11 = BitmapFactory.decodeStream(in);
        } catch (Exception e) {
            Log.e("Error", e.getMessage());
            e.printStackTrace();
        }
        return mIcon11;
    }

    protected void onPostExecute(Bitmap result) {
        bmImage.setImageBitmap(result);
    }    
}

从你的onCreate()方法调用使用:

new DownloadImageTask((ImageView) findViewById(R.id.imageView1))
        .execute(MY_URL_STRING);

结果是一个快速加载的活动和一个稍后根据用户的网络速度显示的imageview。

1. Picasso允许在应用程序中轻松加载图像——通常只需一行代码!

使用它:

implementation 'com.squareup.picasso:picasso:(insert latest version)'

只有一行代码!

Picasso.get().load("http://i.imgur.com/DvpvklR.png").into(imageView);

2. 一个用于Android的图像加载和缓存库，专注于平滑滚动

使用它:

repositories {
   mavenCentral() 
   google()
}

dependencies {
   implementation 'com.github.bumptech.glide:glide:4.11.0'
   annotationProcessor 'com.github.bumptech.glide:compiler:4.11.0'
}

// For a simple view:
Glide.with(this).load("http://i.imgur.com/DvpvklR.png").into(imageView);

3.fresco是一个在Android应用程序上显示图像的强大系统。Fresco负责图像加载和显示，所以你不必这样做。

从壁画开始

    private Bitmap getImageBitmap(String url) {
        Bitmap bm = null;
        try {
            URL aURL = new URL(url);
            URLConnection conn = aURL.openConnection();
            conn.connect();
            InputStream is = conn.getInputStream();
            BufferedInputStream bis = new BufferedInputStream(is);
            bm = BitmapFactory.decodeStream(bis);
            bis.close();
            is.close();
       } catch (IOException e) {
           Log.e(TAG, "Error getting bitmap", e);
       }
       return bm;
    } 

在我看来，最适合完成这项任务的现代图书馆是毕加索广场图书馆。它允许通过URL加载图像到ImageView，只需一行代码:

Picasso.with(context).load("http://i.imgur.com/DvpvklR.png").into(imageView);

我写了一个类来处理这个问题，因为它似乎是我各种项目中反复出现的需求:

https://github.com/koush/UrlImageViewHelper

UrlImageViewHelper will fill an ImageView with an image that is found at a URL. The sample will do a Google Image Search and load/show the results asynchronously. UrlImageViewHelper will automatically download, save, and cache all the image urls the BitmapDrawables. Duplicate urls will not be loaded into memory twice. Bitmap memory is managed by using a weak reference hash table, so as soon as the image is no longer used by you, it will be garbage collected automatically.