Question

我正在创建一个将图像从java服务器发送到android客户端。这是我的android代码：

protected Void doInBackground(Void... arg0) {
try {
     socket = new Socket("192.168.237.1", 6666);
            dataOutputStream = new DataOutputStream(socket.getOutputStream());
            dataInputStream = new DataInputStream(socket.getInputStream());
            // dataOutputStream.writeUTF(textOut.getText().toString());
            String base64Code = dataInputStream.readUTF();

            Log.d("String", ":" + base64Code);
            //
            byte[] decodedString;
            decodedString = Base64.decode(base64Code);
            Log.d("Ds",""+decodedString);
            Log.d("St--", ":" + decodedString.length);
            BitmapFactory.Options options=new BitmapFactory.Options();
            options.inMutable=true;
            bitmap = BitmapFactory.decodeByteArray(decodedString, 0, decodedString.length,options);
            Drawable ob=new BitmapDrawable(getResources(),bitmap);
            imageView = (ImageView) findViewById(R.id.imageView1);
            imageView.setBackgroundDrawable(ob);
            /*//imageView.setImageBitmap(bitmap);
            ByteArrayInputStream input=new ByteArrayInputStream(decodedString);
            bitmap=BitmapFactory.decodeStream(input);
            imageView.setImageBitmap(bitmap);*/
            Log.d("Bitmap",""+bitmap);
        } catch (UnknownHostException e) {
                e.printStackTrace();
        } catch (Exception e) {
                e.printStackTrace();
                Log.d("Error", "" + e);
        }

}

我已经在java usung apache公共编解码器中编码了字节数组，并在android程序中解码。我得到的错误是它在NullPointeException给出了imageView.setBackgroundDrawable (ob);。这段代码中的错误是什么？

Answer 1

您可以从后台线程执行UI操作。它们需要在ui线程中执行。因此，尝试在onPostExecute（）中执行操作。

Answer 2

你需要这样做：

private class MyAsyncTask extends AsyncTask<Void, Void, Bitmap> {

  @Override
  protected Bitmap doInBackground(Void... params) {
    try {
      socket = new Socket("192.168.237.1", 6666);
      dataOutputStream = new DataOutputStream(socket.getOutputStream());
      dataInputStream = new DataInputStream(socket.getInputStream());
      // dataOutputStream.writeUTF(textOut.getText().toString());
      String base64Code = dataInputStream.readUTF();

      Log.d("String", ":" + base64Code);
      //
      byte[] decodedString;
      decodedString = Base64.decode(base64Code);
      Log.d("Ds",""+decodedString);
      Log.d("St--", ":" + decodedString.length);
      BitmapFactory.Options options=new BitmapFactory.Options();
      options.inMutable=true;
      bitmap = BitmapFactory.decodeByteArray(decodedString, 0, decodedString.length,options);

      return bitmap;

      /*//imageView.setImageBitmap(bitmap);
      ByteArrayInputStream input=new ByteArrayInputStream(decodedString);
      bitmap=BitmapFactory.decodeStream(input);
      imageView.setImageBitmap(bitmap);*/
      Log.d("Bitmap",""+bitmap);
    } catch (UnknownHostException e) {
      e.printStackTrace();
    } catch (Exception e) {
      e.printStackTrace();
      Log.d("Error", "" + e);
    }

    return null;
  }

  @Override
  protected void onPostExecute(Bitmap bitmap) {
    if (bitmap != null) {
      Drawable ob =new BitmapDrawable(getResources(), bitmap);
      imageView = (ImageView) findViewById(R.id.imageView1);
      imageView.setBackgroundDrawable(ob);
    } else {
      // error
    }
  }

}

将位图图像设置为ImageView时出错

2 个答案: