If you want to set an ImageView's resource from a web URL without using external libraries like Picasso, you can use the Android `AsyncTask` to download the image and set it in the ImageView. Here's an example:

```java
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;
import android.widget.ImageView;
import java.io.InputStream;
import java.io.IOException;
import java.net.HttpURLConnection;
import java.net.URL;

// Assuming you have an ImageView with the id "imageView" in your layout XML.
ImageView imageView = findViewById(R.id.imageView);

String imageUrl = "https://www.example.com/your_image.jpg";

new DownloadImageTask(imageView).execute(imageUrl);

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

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

    @Override
    protected Bitmap doInBackground(String... urls) {
        String imageUrl = urls[0];
        Bitmap bitmap = null;
        try {
            URL url = new URL(imageUrl);
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            connection.setDoInput(true);
            connection.connect();
            InputStream input = connection.getInputStream();
            bitmap = BitmapFactory.decodeStream(input);
        } catch (IOException e) {
            e.printStackTrace();
        }
        return bitmap;
    }

    @Override
    protected void onPostExecute(Bitmap result) {
        if (result != null) {
            imageView.setImageBitmap(result);
        }
    }
}
```

In this code, we create an `AsyncTask` called `DownloadImageTask` that downloads the image from the web in the background. In the `onPostExecute` method, we set the downloaded image into the ImageView. Make sure to replace `"https://www.example.com/your_image.jpg"` with the actual URL of the image you want to display.