Question

我想在结果为空时显示默认图片，这是我的尝试：

getBitmapFromURL和一个使用它的类：

    public static Bitmap getBitmapFromURL(String src) {
        try {
            URL url = new URL(src);
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            connection.setDoInput(true);
            connection.connect();
            InputStream input = connection.getInputStream();
            Bitmap myBitmap = BitmapFactory.decodeStream(input);
            connection.disconnect();
            return myBitmap;
        } catch (IOException e) {
//          tasvirdimg.setImageResource(R.drawable.p3_books);
            e.printStackTrace();
            return null;
        }
    }
}
class RetrievePic extends AsyncTask<String, String, Bitmap>{

    @Override
    protected Bitmap doInBackground(String... urls) {
        String url = urls[0];
        return JSONCommands.getBitmapFromURL(url);
    }

}

在ListAdapter执行课程：

//      tasvirlimg.setImageResource(R.drawable.p3_books);
        RetrievePic retPic = new RetrievePic();
        retPic.execute(JSONCommands.firstURL + MainActivity.books_array.get(position).tasvir);
        Bitmap img = null;
        try {
            img = retPic.get();
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            tasvirlimg.setImageResource(R.drawable.p3_books);
            e.printStackTrace();
        } catch (ExecutionException e) {
            // TODO Auto-generated catch block
            tasvirlimg.setImageResource(R.drawable.p3_books);
            e.printStackTrace();
        }

        tasvirlimg.setImageBitmap(img);

当图书图片为空时，它不会显示任何内容，但我希望它显示默认的图片来源为R.drawable.p3_books。请帮忙。谢谢。

Answer 1

你可以试试这个：

if(img == null) 
{ 
     tasvirlimg.setImageDrawable(R.drawable.p3_books); 
}
else
{ 
     tasvirlimg.setImageBitmap(img);
}

Answer 2

为什么不在xml中设置项目的默认pic，然后在result不为null时替换默认pic

  <ImageView 
     ...
         android:src="@drawable/p3_books"
        />

编辑：

        class RetrievePic extends AsyncTask<String, String, Bitmap>{

     final image = (ImageView) findViewById(R.id.limg_tasvir);

            @Override
            protected Bitmap doInBackground(String... urls) {
                String url = urls[0];
                return JSONCommands.getBitmapFromURL(url);
            }

            @Override
                    protected void onPreExecute() {
                         runOnUiThread(new Runnable() {
                                @Override
                                public void run() {
                        image.setBackgroundResource(R.drawable.p3_books);
                                }
                            });

        }
}

Answer 3

你想要做的是你的适配器的getView()方法的实现，像这样，

...
final imageView = ...;
imageView.setImageBitmap(defaultBitmap);
new AsyncTask<Void,Void,Bitmap>() {
  public Bitmap doInBackground(Void... params) {
    // get bitmap from `net, or return null if failure
  }

  public void onPostExecute(Bitmap result) {
    if (result != null) {
      imageView.setBitmap(result);
    }
  }
}.execute();

这样，默认设置。如果您碰巧获得了网络结果，请更改默认值。

如何在android中的列表中设置默认图片？

3 个答案: