Question

我有一个url传递给一个活动，我试图从url全屏显示图像，但它抛出一个主网络线程异常。

据我所知，我相信我必须把这个方法放在异步任务中，但我似乎根本无法理解它。那么我如何将这个方法放在异步任务中呢？

FullScreenImageView.java

public class FullscreenImageView extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    String url = getIntent().getStringExtra("SelectedImageURL");



    try {
        ImageView i = (ImageView)findViewById(R.id.imgView);
        Bitmap bitmap = BitmapFactory.decodeStream((InputStream)new URL(url).getContent());
        i.setImageBitmap(bitmap);
    } catch (MalformedURLException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }

}
}

Answer 1

它应该是这样的。在doInBackground中，您可以获得图片，并在onPostExecute中设置图片

private class DownloadFilesTask extends AsyncTask<String, Void, Bitmap>  {
     @Override
     protected Bitmap doInBackground(String... urls) {
          Bitmap bitmap = null; 
          try {
              bitmap = BitmapFactory.decodeStream((InputStream)new URL(urls[0]).getContent());
          } catch (MalformedURLException e) {
               e.printStackTrace();
          } catch (IOException e) {
             e.printStackTrace();
          }
          return bitmap;
     }
     @Override
     protected void onPostExecute(Bitmap bitmap) {
        ImageView i = (ImageView)findViewById(R.id.imgView);
        i.setImageBitmap(bitmap);
     }
 }

然后，您在onCreate方法

中调用它

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    String url = getIntent().getStringExtra("SelectedImageURL");
    new DownloadFilesTask ().execute(url); 
}

Answer 2

将您的网络任务放在AsyncTask的doInBackground()方法中，如下所示：

@Override
    protected Void doInBackground(Void... params) {
        // TODO Auto-generated method stub

try {
        //ImageView i = (ImageView)findViewById(R.id.imgView);Put this line in onPreExecute() method
        Bitmap bitmap = BitmapFactory.decodeStream((InputStream)new URL(url).getContent());
       // i.setImageBitmap(bitmap);//and this one on postExecute() method
    } catch (MalformedURLException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }

}

Answer 3

使用findViewById（）初始化yourImageView后使用Picasso;

Picasso.with(context).load(url).into(yourImageView)

如何在异步任务中实现此图像视图？

3 个答案: