问题

我基本上在遵循一个用于学习Android Studio的教程，该教程使用AsyncTask类来执行后台任务，例如HttpURLConnection。但问题是它产生了许多错误，后来我发现该类已被弃用。那么有什么替代方案吗？

import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;

public class MainActivity extends AppCompatActivity {

    public class DownloadingTask extends AsyncTask<String, Void, String> {
        @Override
        protected String doInBackground(String... urls) {
            String result = "";
            HttpURLConnection urlConnection = null;
            URL url;
            try {
                url = new URL(urls[0]);
                urlConnection = (HttpURLConnection) url.openConnection();
                InputStream in = urlConnection.getInputStream();
                InputStreamReader reader = new InputStreamReader(in);
                int data = reader.read();
                while (data != -1) {
                    char current = (char) data;
                    result = result + current;
                    data = reader.read();
                }
                return result;
            } catch (IOException e) {
                e.printStackTrace();
                return "Failed";
            } finally {
                if (urlConnection != null) {
                    urlConnection.disconnect();
                }
            }
        }
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        DownloadingTask task = new DownloadingTask();
        String s = null;
        try {
            s = task.execute("http://www.android.com/").get();
        } catch (Exception e) {
            e.printStackTrace();
        }
        Log.i("Msg", s);
    }
}

注意：上述代码中已经做了一些修改以替代AsyncTask的使用，特别是在网络连接关闭方面。这个修改将确保在下载完成后正确关闭连接，以避免资源泄漏。

public class MainActivity extends AppCompatActivity {
public class DownloadingTask extends AsyncTask<String, Void, String>
{
@Override
protected String doInBackground(String... urls)
{
String result="";
HttpURLConnection urlConnection=null;
URL url;
try{
url=new URL(urls[0]);
urlConnection=(HttpURLConnection)url.openConnection();
InputStream in;
in = urlConnection.getInputStream();
InputStreamReader reader=new InputStreamReader(in);
int data=reader.read();
while (data!=-1)
{
char current=(char) data;
result = result + current;
data=reader.read();
}
return result;
}
catch (Exception e)
{
e.printStackTrace();
return "Failed";
}
}
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
DownloadingTask task= new DownloadingTask();
String s=null;
try {
s = task.execute("http://www.android.com/").get();
}
catch (Exception e)
{
e.printStackTrace();
}
Log.i("Msg",s);
}
}

答案1

得分: 0

以下是翻译好的部分：

这是一个示例，展示了如何使用AsynkTask下载图像。

private class DownLoadImageTask extends AsyncTask<String, Void, Bitmap> {
    ImageView imageView;

    DownLoadImageTask(ImageView imageView) {
        this.imageView = imageView;
    }

    protected Bitmap doInBackground(String... urls) {
        String urlOfImage = urls[0];
        Bitmap logo = null;
        try {
            InputStream is = new URL(urlOfImage).openStream();
            logo = BitmapFactory.decodeStream(is);
        } catch (Exception e) { // 捕获下载异常
            Log.v("download", e.getMessage());
        }
        return logo;
    }

    protected void onPostExecute(Bitmap result) {
        imageView.setImageBitmap(result);
    }
}

这是如何运行它的方法：

new DownLoadImageTask(img).execute(imageUrl);

任何更新都在onPostExecute方法中进行，因为它在UI线程上运行。

是的，您说得对。AsynkTask已被弃用。您可以使用LoaderManager和Java Executor，或者Volley、Retrofit库。

对于下载图像，您可以使用Picasso和Glide库。

private class DownLoadImageTask extends AsyncTask<String, Void, Bitmap> {
ImageView imageView;
DownLoadImageTask(ImageView imageView) {
this.imageView = imageView;
}
protected Bitmap doInBackground(String... urls) {
String urlOfImage = urls[0];
Bitmap logo = null;
try {
InputStream is = new URL(urlOfImage).openStream();
logo = BitmapFactory.decodeStream(is);
} catch (Exception e) { // Catch the download exception
Log.v("download", e.getMessage());
}
return logo;
}
protected void onPostExecute(Bitmap result) {
imageView.setImageBitmap(result);
}
}

new DownLoadImageTask(img).execute(imageUrl);