Question

我意识到为了使我的应用程序的一部分工作，我可能需要在一个单独的线程上运行它。在此之后我的选择似乎是Asynch和Threads，我认为Asynch似乎是更好的选择，因为我没有使用线程的经验。我试图在一个单独的线程上运行petrolPriceString但我没有这方面的知识。任何有关这方面的帮助将不胜感激

编辑：我整个班级的添加

package org.me.myandroidstuff;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLConnection;

//import android.app.Activity;
import android.os.Bundle;
import android.widget.TextView;

public class PetrolPriceActivity extends Menu 
{
    private TextView response;
    private TextView errorText;
    private String result;
    private String petrolPriceURL;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) 
    {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.list);

        Bundle extras = getIntent().getExtras();
        if(extras!=null){
        petrolPriceURL =extras.getString("URLString");
        }
        // Get the TextView object on which to display the results
        response = (TextView)findViewById(R.id.error);
        response = (TextView)findViewById(R.id.title);
        try
        {
            // Get the data from the RSS stream as a string
            result =  petrolPriceString(petrolPriceURL);

            // Do some processing of the data to get the individual parts of the RSS stream
            // At some point put this processing into a separate thread of execution
            // Display the string in the TextView object just to demonstrate this capability
            // This will need to be removed at some point
            response.setText(result);
        }
        catch(IOException ae)
        {
            // Handle error
            response.setText("Error");
            // Add error info to log for diagnostics
            errorText.setText(ae.toString());
        } 

    }

    // End of onCreate

    // Method to handle the reading of the data from the RSS stream
    private static String petrolPriceString(String urlString)throws IOException
    {
        String result = "";
        InputStream anInStream = null;
        int response = -1;
        URL url = new URL(urlString);
        URLConnection conn = url.openConnection();

        // Check that the connection can be opened
        if (!(conn instanceof HttpURLConnection))
                throw new IOException("Not an HTTP connection");
        try
        {
            // Open connection
            HttpURLConnection httpConn = (HttpURLConnection) conn;
            httpConn.setAllowUserInteraction(false);
            httpConn.setInstanceFollowRedirects(true);
            httpConn.setRequestMethod("GET");
            httpConn.connect();
            response = httpConn.getResponseCode();
            // Check that connection is Ok
            if (response == HttpURLConnection.HTTP_OK)
            {
                // Connection is OK so open a reader 
                anInStream = httpConn.getInputStream();
                InputStreamReader in= new InputStreamReader(anInStream);
                BufferedReader bin= new BufferedReader(in);

                // Read in the data from the RSS stream
                String line = new String();
                while (( (line = bin.readLine())) != null)
                {
                    result = result + "\n" + line;
                }
            }
        }
        catch (Exception ex)
        {
                throw new IOException("Error connecting");
        }

        // Return result as a string for further processing
        return result;
    }
    // End of petrolPriceString
 // End of Activity class
}

我的应用程序此刻是没有错误但是我得到的输出不是我想要的所以我相信一个单独的线程就是答案

Answer 1

AsyncTask对于在后台进行慢速工作（如网络交互）以及在主/ UI线程上进行最后的处理/交互操作非常有用。如果我正确理解您的请求，您可以尝试这样的事情：

new AsyncTask<String, Void, String>() {
    @Override protected String doInBackground(String... params) {
        // we do this part in the background on another thread
        return petrolPriceString(params[0]);
    }
    @Override protected void onPostExecute(String result) {
        // result is the value returned from our call to petrolPriceString
        // anything we put in here is done on the main/UI thread
    }
}.execute(urlString);

如果要捕获petrolPriceString抛出的异常，并相应地执行一些逻辑，一种可能的解决方案是将其保存为AsyncTask中的本地成员。像下面这样......

new AsyncTask<String, Void, String>() {
    IOException exception = null;
    @Override protected String doInBackground(String... params) {
        try {
            return petrolPriceString(params[0]);
        } catch (IOException e) {
            exception = e;
            return null;
        }
    }
    @Override protected void onPostExecute(String result) {
        if (exception != null) {
            // handle our exception
        } else {
            // handle our result
        }
    }
}.execute(urlString);

Android：方法的异步线程

1 个答案: