获取ProgressBar时出现空指针异常，大神们指教啦

Question

有一DownloadTask类代码如下
public class DownloadTask extends AsyncTask<String, Integer, Integer> {
     ................    private Context context;
    LayoutInflater factory = LayoutInflater.from(context);
    View layout = factory.inflate(R.layout.activity_main, null);
    ProgressBar downloadProgress = (ProgressBar) layout.findViewById(R.id.download_progress);    public DownloadTask(DownloadListener listener, Context context) {
        this.listener = listener;
        this.context = context;
    }....................
}
在DownloadService中使用
private DownloadTask downloadTask ；
downloadTask = new DownloadTask(listener,DownloadService.this);红色字体为空指针位置大神们帮忙看看吧，万分感谢！！！

Answer 1

public class DownloadTask extends AsyncTask<String, Integer, Integer> {
     ................    private Context context;
    LayoutInflater factory = LayoutInflater.from(context);
    View layout = factory.inflate(R.layout.activity_main, null);
    ProgressBar downloadProgress = (ProgressBar) layout.findViewById(R.id.download_progress);    public DownloadTask(DownloadListener listener, Context context) {
        this.listener = listener;
        this.context = context;
factory = LayoutInflater.from(context);
    View layout = factory.inflate(R.layout.activity_main, null);
    ProgressBar downloadProgress = (ProgressBar) layout.findViewById(R.id.download_progress);    }
....................
}

Answer 2

public class DownloadTask extends AsyncTask<String, Integer, Integer> {
     ................    private Context context;
    LayoutInflater factory;
    View layout ;
    ProgressBar downloadProgress;    public DownloadTask(DownloadListener listener, Context context) {
        this.listener = listener;
        this.context = context;
       factory = LayoutInflater.from(context);
    layout = factory.inflate(R.layout.activity_main, null);
    downloadProgress = (ProgressBar) layout.findViewById(R.id.download_progress);
    }
....................
}