Question

我正在尝试编写我的第一个Android应用程序，需要将网页的文本作为字符串显示在TextView中。我在StackOverflow上找到了一些示例，但由于某些原因，它们似乎都不适用于我。当我单击按钮以检索文本时，应用程序崩溃。这是我现在所拥有的（基于Get text from web page to string的代码）：

MainActivity.java文件



    public class MainActivity extends ActionBarActivity {

      Button testbutton;
      Button btnReset;
      TextView serverMsgViewComponent;
      @Override
      protected void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          setContentView(R.layout.activity_main);
          addListenerOnButton();
      }

      public void addListenerOnButton() {
          testbutton = (Button) findViewById(R.id.btnClickme);
          btnReset = (Button) findViewById(R.id.btnResetText);
          serverMsgViewComponent = (TextView) findViewById(R.id.serverMsgView);
          serverMsgViewComponent.setText("Custom text");
          final ReadWebpageAsyncTask readpage = new ReadWebpageAsyncTask();
          btnReset.setOnClickListener(new OnClickListener() {
              @Override
              public void onClick(View arg0) {
                  serverMsgViewComponent.setText("Server message placeholder");
              }
          });
          testbutton.setOnClickListener(new OnClickListener() {
              @Override
              public void onClick(View arg0) {
                  serverMsgViewComponent.setText("Retrieving message from server...");
                  readpage.readWebpage();
              }

          });

      }

      //some default code here
    }

ReadWebpageAsyncTask.java



public class ReadWebpageAsyncTask extends Activity {
    private TextView textView;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        textView = (TextView) findViewById(R.id.serverMsgView);
    }

    private class DownloadWebPageTask extends AsyncTask<String, Void, String> {
        @Override
        protected String doInBackground(String... urls) {
            String response = "";
            for (String url : urls) {
                DefaultHttpClient client = new DefaultHttpClient();
                HttpGet httpGet = new HttpGet(url);
                try {
                    HttpResponse execute = client.execute(httpGet);
                    InputStream content = execute.getEntity().getContent();

                    BufferedReader buffer = new BufferedReader(
                            new InputStreamReader(content));
                    String s = "";
                    while ((s = buffer.readLine()) != null) {
                        response += s;
                    }

                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
            return response;
        }

        @Override
        protected void onPostExecute(String result) {
            textView.setText(Html.fromHtml(result));
        }
    }

    public void readWebpage() {
        DownloadWebPageTask task = new DownloadWebPageTask();
        task.execute(new String[] { "http://hglstudio.com/workspace/server.htm" });

    }
}

public class ReadWebpageAsyncTask extends Activity {
    private TextView textView;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        textView = (TextView) findViewById(R.id.serverMsgView);
    }

    private class DownloadWebPageTask extends AsyncTask<String, Void, String> {
        @Override
        protected String doInBackground(String... urls) {
            String response = "";
            for (String url : urls) {
                DefaultHttpClient client = new DefaultHttpClient();
                HttpGet httpGet = new HttpGet(url);
                try {
                    HttpResponse execute = client.execute(httpGet);
                    InputStream content = execute.getEntity().getContent();

                    BufferedReader buffer = new BufferedReader(
                            new InputStreamReader(content));
                    String s = "";
                    while ((s = buffer.readLine()) != null) {
                        response += s;
                    }

                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
            return response;
        }

        @Override
        protected void onPostExecute(String result) {
            textView.setText(Html.fromHtml(result));
        }
    }

    public void readWebpage() {
        DownloadWebPageTask task = new DownloadWebPageTask();
        task.execute(new String[] { "http://hglstudio.com/workspace/server.htm" });

    }
}

Answer 1

所以，我说我从另一个SO讨论中复制了代码，这段代码对我不起作用，我需要帮助找出原因。相反，我把我的问题标记为另一个我从中获取代码的副本，我的问题也被低估了。谢谢，StackOverflow！

现在，我自己发现了这个问题（很开心！）。问题在于域名由于某种原因未能解析为IP地址，然后引发了错误。解决方案是首先通过访问URL一次“初始化”域，然后尝试在第二次尝试时下载文本。

所以我先调用这个函数：

private void initializeDns(String url) {
    try {
        InetAddress address = InetAddress.getByName(url);
    } catch (UnknownHostException e) {
        e.printStackTrace();
    }
}

获取网页文字

1 个答案: