Downloading and setting a wallpaper

问题

I have this little piece of code and I want to achieve this: program should set a wallpaper from linked image.

ImgDownload:

public class ImgDownload extends AsyncTask {
        private String requestUrl;
        private ImageView view;
        private Bitmap pic;

        private ImgDownload(String requestUrl, ImageView view) {
            this.requestUrl = requestUrl;
            this.view = view;
        }

        @Override
        protected Object doInBackground(Object... objects) {
            try {
                URL url = new URL(requestUrl);
                URLConnection conn = url.openConnection();
                pic = BitmapFactory.decodeStream(conn.getInputStream());
            } catch (Exception ex) {
            }
            return null;
        }

        @Override
        protected void onPostExecute(Object o) {
            view.setImageBitmap(pic);
        }
    }

main

public class MainActivity extends Activity {

    private ImageView img;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        img= (ImageView)findViewById(R.id.img);

//!!!! This is where I am stuck :)
        Object s = new ImgDownload("http://images1.wikia.nocookie.net/__cb20120402213849/masseffect/images/4/42/Uncharted_Worlds_Codex_Image.jpg",img );
    }



    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

}

How to instantiate/create this class in my mainActivity, so it could download img from link? Any help suggestions, thoughts, will be appreciated :)

回答1:

You execute this AsyncTask like this:

ImgDownload downloader = new ImgDownload("http://images1.wikia.nocookie.net/__cb20120402213849/masseffect/images/4/42/Uncharted_Worlds_Codex_Image.jpg",img);
downloader.execute();

But I would not recommend using your code as it will produce memory leaks. For example try to rotate your device while it is downloading an image. I guarantee you your application will crash. Plus AsyncTask is a generic class. You could use that to make your code a little simpler. Here is my improved image download task:

public class ImgDownload extends AsyncTask<Void, Void, Bitmap> { // Use Generics
    private final String requestUrl;
    private final WeakReference<ImageView> imageViewReference; // Use WeakReference to prevent memory leaks

    public ImgDownload(String requestUrl, ImageView view) {
        this.requestUrl = requestUrl;
        this.imageViewReference = new WeakReference<ImageView>(view);
    }

    @Override
    protected Bitmap doInBackground(Void... objects) {
        try {
            URL url = new URL(requestUrl);
            URLConnection conn = url.openConnection();
            return BitmapFactory.decodeStream(conn.getInputStream()); // Return bitmap instead of using global variable
        } catch (Exception ex) {
        }
        return null;
    }

    @Override
    protected void onPostExecute(Bitmap bitmap) {
        ImageView imageView = imageViewReference.get();
        if(imageView != null && bitmap != null) { // Check if image or ImageView are null
            imageView.setImageBitmap(bitmap);
        }
    }
}

回答2:

new ImgDownload("http://images1.wikia.nocookie.net/__cb20120402213849/masseffect/images/4/42/Uncharted_Worlds_Codex_Image.jpg", MainActivity.img).execute();

来源：https://stackoverflow.com/questions/20174429/downloading-and-setting-a-wallpaper

标签

android

image

wallpaper