Question

package info.testing;

import java.io.IOException;

import org.jsoup.Jsoup;
import org.jsoup.nodes.Document;
import org.jsoup.select.Elements;

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.webkit.WebView;
import android.widget.Toast;

public class SoupActivity extends Activity {

private static final String TAG = "SoupActivity";
private static final String DATA = null;
private String data = null;

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    if(savedInstanceState != null)
    {
        data = savedInstanceState.getString(DATA);
        showResults();
    }
    else
    {
        parsePage();
    }
}

protected void parsePage(){
    Document doc = null;
    try {
        doc = Jsoup.connect("http://www.mydata.html").get();
        Toast.makeText(this, R.string.success, Toast.LENGTH_SHORT).show();
    } catch (IOException e) {
        Toast.makeText(this, R.string.error, Toast.LENGTH_SHORT).show();
    }

    Elements rows = doc.select("tr[class]");

    data = "<table>" + rows.toString() + "</table>";
    showResults();
}

protected void showResults(){
    WebView web = (WebView)findViewById(R.id.web);
    web.loadData(data, "text/html", "utf-8");
}

@Override
public void onSaveInstanceState(Bundle savedInstanceState){
    savedInstanceState.putString(DATA, data);
    super.onSaveInstanceState(savedInstanceState);
}

@Override
public void onRestoreInstanceState(Bundle savedInstanceState){
    if(savedInstanceState != null)
    {
        data = savedInstanceState.getString(DATA);
    }
    super.onRestoreInstanceState(savedInstanceState);
}
}

Flash / Flex开发人员在这里开始进入Android开发阶段，我必须承认我到目前为止都很喜欢它，但显然需要花费很长时间来解决为什么会发生事情的方式。

所以我遇到的问题是我的应用程序在没有Internet连接的情况下崩溃了 - 应用程序（process.testing）意外停止了。只有在没有互联网连接时才会发生这种情况，如果有互联网连接则完美无缺。我的代码访问Internet的唯一部分是在try catch块中，任何人都可以看到我做错了什么或者在没有Internet连接时如何处理错误？

Answer 1

您可以使用此功能查看连接是否可用：

/**
* Check the network state
* @param context context of application
* @return true if the phone is connected
*/
public static boolean isConnected(Context context) {
    ConnectivityManager cm = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo netInfo = cm.getActiveNetworkInfo();
    if (netInfo != null && netInfo.isConnected()) {
        return true;
    }
    return false;
}

Answer 2

如果您没有互联网连接，doc可能为空，而您获得NullPointerException，因为您没有检查此案例：

Document doc = null;
try {
    // connect throws an exception, doc still null
    doc = Jsoup.connect("http://www.mydata.html").get();
    Toast.makeText(this, R.string.success, Toast.LENGTH_SHORT).show();
} catch (IOException e) {
    Toast.makeText(this, R.string.error, Toast.LENGTH_SHORT).show();
}

// dereferencing null (doc) throws NullPointerException
Elements rows = doc.select("tr[class]");

Android - app force在没有Internet连接时关闭

2 个答案: