从Android中的网址下载图片

Question

I have to download an image from an url. Do you recommend Bitmap or Drawable? Whatever, I have tried twice, but those don't work. Do you know what could be the problem?? (I have written the internet and the external storage permissions). You will see that I recieve the URL by a JSON object, but I was recieved correctly.

If I want to recieve it in a Drawable element:

protected Drawable getDrawable()
    {
        try{
            JSONObject jsonResponse = new JSONObject(content);
            String src=jsonResponse.getString(data);
            InputStream is = (InputStream)new URL(src).getContent();
            Drawable d=Drawable.createFromStream(is, "basket.png");
            return d;
        }
        catch(Exception e)
        {
            String err="This is the error: ";
            Log.e(err,e.getMessage());
            //e.printStackTrace();
            return null;
        }
    }

If I want to recieve it un a Bitmap element:

protected Bitmap getBitMap()
    {
        try{
            JSONObject jsonResponse = new JSONObject(content);
            String src=jsonResponse.getString(data);
            java.net.URL url = new java.net.URL(src);
            HttpURLConnection con=(HttpURLConnection)url.openConnection();
            con.setDoInput(true);
            con.connect();
            InputStream input=con.getInputStream();
            Bitmap myBitmap=BitmapFactory.decodeStream(input);
            return myBitmap;
        }
        catch(Exception e){
            String err="This is the error: ";
            Log.e(err,e.getMessage());
            //e.printStackTrace();
            return null;
        }
    }

This is where I have the ImageView:

public class Accedido extends AppCompatActivity {

    ImageView imagen;
    Button ok;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_accedido);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        imagen=(ImageView)findViewById(R.id.Img);
        ok=(Button)findViewById(R.id.btnOk);
        ok.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Bitmap img=null;
                Ajax im=new Ajax();
                try {
                    String imagen = im.execute(MainActivity.IP_ADDRESS + "Imagen").get();
                    LeerConsulta lec = new LeerConsulta(imagen, "img");
                    //img=lec.getBitMap();
                    /*String res=lec.getContent();
                    String res2=lec.getData();
                    Toast.makeText(Accedido.this, "Content:"+res+"Data:"+res2, Toast.LENGTH_LONG).show();*/
                    img=lec.getBitMap();
                }
                catch(Exception exc) {
                    Toast.makeText(Accedido.this, exc.getMessage(), Toast.LENGTH_SHORT).show();
                }
                imagen.setImageBitmap(img);
            }
        });
    }

When I run those codes, the program throws me an error which says println needs a message ...But I have never written in the program a system.out.println

Answer 1

use Asynck task to download image .

 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 mIcon = null;
            try {
                InputStream in = new java.net.URL(urldisplay).openStream();
                mIcon = BitmapFactory.decodeStream(in);
            } catch (Exception e) {
                Log.e("Error", e.getMessage());
                e.printStackTrace();
            }
            return mIcon;
        }

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

You can refer this link http://www.wingnity.com/blog/android-json-parsing-and-image-loading-tutorial/

Answer 2

Bitmap is better in my opinion. Try this out. Make sure that the URL you get from the JSON is only of image.

JSONObject jsonResponse = new JSONObject(content);
String src=jsonResponse.getString(data);
java.net.URL url = new java.net.URL(src);
Bitmap bitmap = BitmapFactory.decodeStream(url.openConnection().getInputStream());

Moreover, Universal Image Loader library is also available. Try that as well.

Answer 3

Volley is an HTTP library that makes networking for Android apps easier and most importantly, faster. At a high level, you use Volley by creating a RequestQueue and passing it Request objects. The RequestQueue manages worker threads for running the network operations, reading from and writing to the cache, and parsing responses.

You can use Volley for Image downloading:

Add repo in your Gradle:

compile 'com.android.volley:volley:1.0.0'

You need to add this code, in your class where ImageView is present, just add the code (In download button if you have any):

ImageRequest imageRequest = new ImageRequest(your_image_url, new Response.Listener<Bitmap>() {
        @Override
        public void onResponse(final Bitmap response) {
                    your_image_view.setImageBitmap(response);
        }
    }, 0, 0, ImageView.ScaleType.CENTER_INSIDE, null, new Response.ErrorListener() {
        @Override
        public void onErrorResponse(VolleyError error) {
            Toast.makeText(your_activity_context.this, error.toString(), Toast.LENGTH_LONG).show();
        }
    });

    RequestQueue requestQueue = Volley.newRequestQueue(your_activity_context.this);
    requestQueue.add(imageRequest);

Courtesy Google.com

Answer 4

您可以使用Glide库将图像直接从URL下载到图像视图中。

Glide.with(context).load(url).diskCacheStrategy(DiskCacheStrategy.ALL).into(imageView);