java - Android中APP处于状态时如何检查互联网连接？

Question

这个问题已经有答案了:

unfortunately app is getting stopped while checking for network (3 个回答)

已关闭 7 年前。

我是 Android 新手。这是我知道的一个基本问题，但我找不到任何合适的答案。

这是我的代码...

public class MainActivity extends ActionBarActivity {
// Declare Variables
JSONObject jsonobject;
JSONArray jsonarray;
ListView listview;
ListViewAdapter adapter;
ProgressDialog mProgressDialog;
ArrayList<HashMap<String, String>> arraylist;
static String url = "https://www.googleapis.com/youtube/v3/search?part=snippet&maxResult=30&q=natok+bangla+mosharrof+karim&key=AIzaSyCR40QlsuX0aFfBV-wEPDsH_jxna1tDFRA";

static String VIDEO_ID = "videoId";
static String TITLE = "title";
//static String DESCRIPTION = "description";
static String THUMBNAILS = "img";

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    // Get the view from listview_main.xml
    setContentView(R.layout.listview_main);
    new DownloadJSON().execute();
    Object localObject = getIntent().getStringExtra("title");
    if (!isOnline())
    {
        localObject = new AlertDialog.Builder(this);
        ((AlertDialog.Builder)localObject).setTitle("Internet Alert");
        ((AlertDialog.Builder)localObject).setMessage("Please Check internet Conectivity and try again.");
        ((AlertDialog.Builder)localObject).setPositiveButton("OK", new DialogInterface.OnClickListener()
        {
            public void onClick(DialogInterface paramAnonymousDialogInterface, int paramAnonymousInt)
            {
                paramAnonymousDialogInterface.cancel();
            }
        });
        ((AlertDialog.Builder)localObject).create().show();
    }
    // Execute DownloadJSON AsyncTask





}
public boolean isOnline()
{
    NetworkInfo localNetworkInfo = ((ConnectivityManager)getSystemService(Context.CONNECTIVITY_SERVICE)).getActiveNetworkInfo();
    boolean bool;
    if ((localNetworkInfo == null) || (!localNetworkInfo.isAvailable()) || (!localNetworkInfo.isConnectedOrConnecting())) {
        bool = false;
    } else {
        bool = true;
    }
    return bool;
}

// DownloadJSON AsyncTask
private class DownloadJSON extends AsyncTask<Void, Void, Void> {

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        // Create a progressdialog
        mProgressDialog = new ProgressDialog(MainActivity.this);
        // Set progressdialog title
        mProgressDialog.setTitle("Your Youtube Video is");
        // Set progressdialog message
        mProgressDialog.setMessage("Loading...");
        mProgressDialog.setIndeterminate(false);
        // Show progressdialog
        mProgressDialog.show();
    }

    @Override
    protected Void doInBackground(Void... params) {
        // Create an array
        arraylist = new ArrayList<HashMap<String, String>>();

        // Retrieve JSON Objects from the given URL address

        String query = "bangla natok 2015";
        query = query.replace(" ", "+");
        try {
            query = URLEncoder.encode(query, "utf-8");
        } catch (UnsupportedEncodingException e) {
            // TODO Auto-generated catch block
            //e.printStackTrace();
        }

        jsonobject = JSONfunctions.getJSONfromURL("https://www.googleapis.com/youtube/v3/search?part=id%2Csnippet&q=natok+2015&maxResults=50&key=AIzaSyCR40QlsuX0aFfBV-wEPDsH_jxna1tDFRA");

        try {
            // Locate the array name in JSON
            JSONArray jsonarray = jsonobject.getJSONArray("items");

            for (int i = 0; i < jsonarray.length(); i++) {
                HashMap<String, String> map = new HashMap<String, String>();
                jsonobject = jsonarray.getJSONObject(i);
                // Retrive JSON Objects
                JSONObject jsonObjId = jsonobject.getJSONObject("id");
                map.put("videoId", jsonObjId.getString("videoId"));
                map.put ("img","http://img.youtube.com/vi/" + VIDEO_ID + "/hqdefault.jpg");

                JSONObject jsonObjSnippet = jsonobject.getJSONObject("snippet");
                map.put("title", jsonObjSnippet.getString("title"));

                //map.put("description", jsonObjSnippet.getString("description"));
                // map.put("flag", jsonobject.getString("flag"));




                // Set the JSON Objects into the array
                arraylist.add(map);
            }
        } catch (JSONException e) {
            Log.e("Error", e.getMessage());
            e.printStackTrace();
        }
        return null;
    }

    @Override
    protected void onPostExecute(Void args) {
        // Locate the listview in listview_main.xml
        listview = (ListView) findViewById(R.id.listview);
        // Pass the results into ListViewAdapter.java
        adapter = new ListViewAdapter(MainActivity.this, arraylist);
        // Set the adapter to the ListView
        listview.setAdapter(adapter);
        // Close the progressdialog
        mProgressDialog.dismiss();
    }
}

我检查了此代码 100 次，但找不到任何错误。但是当它在设备上运行时，它会停止为“不打开我的主布局”。

我还在 list 中添加了一些权限。

<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE"></uses-permission>

现在有人能发现这个问题吗？

请我堆在这里。

Answer 1

试试这个

AndroidManifest.xml

  <?xml version="1.0" encoding="utf-8"?>
  <manifest xmlns:android="http://schemas.android.com/apk/res/android"
      package="com.example.detectinternetconnection"
      android:versionCode="1"
      android:versionName="1.0" >

      <uses-sdk android:minSdkVersion="8" />

      <application
          android:icon="@drawable/ic_launcher"
          android:label="@string/app_name" >
          <activity
              android:name=".AndroidDetectInternetConnectionActivity"
              android:label="@string/app_name" >
              <intent-filter>
                  <action android:name="android.intent.action.MAIN" />

                  <category android:name="android.intent.category.LAUNCHER" />
              </intent-filter>
          </activity>
      </application>

      <!-- Internet Permissions -->
      <uses-permission android:name="android.permission.INTERNET" />

      <!-- Network State Permissions -->
      <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />

  </manifest>

ConnectionDetector.java

  import android.content.Context;
  import android.net.ConnectivityManager;
  import android.net.NetworkInfo;

  public class ConnectionDetector {

      private Context _context;

      public ConnectionDetector(Context context){
          this._context = context;
      }

      public boolean isConnectingToInternet(){
          ConnectivityManager connectivity = (ConnectivityManager) _context.getSystemService(Context.CONNECTIVITY_SERVICE);
            if (connectivity != null) 
            {
                NetworkInfo[] info = connectivity.getAllNetworkInfo();
                if (info != null) 
                    for (int i = 0; i < info.length; i++) 
                        if (info[i].getState() == NetworkInfo.State.CONNECTED)
                        {
                            return true;
                        }

            }
            return false;
      }
  }

主要 Activity

import android.app.Activity;
import android.app.AlertDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

public class AndroidDetectInternetConnectionActivity extends Activity {

    // flag for Internet connection status
    Boolean isInternetPresent = false;

    // Connection detector class
    ConnectionDetector cd;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        Button btnStatus = (Button) findViewById(R.id.btn_check);

        // creating connection detector class instance
        cd = new ConnectionDetector(getApplicationContext());

        /**
         * Check Internet status button click event
         * */

        // get Internet status
        isInternetPresent = cd.isConnectingToInternet();

        // check for Internet status
        if (isInternetPresent) {
            // Internet Connection is Present
            // make HTTP requests
            showAlertDialog(AndroidDetectInternetConnectionActivity.this, "Internet Connection",
                    "You have internet connection", true);
        } else {
            // Internet connection is not present
            // Ask user to connect to Internet
            showAlertDialog(AndroidDetectInternetConnectionActivity.this, "No Internet Connection",
                    "You don't have internet connection.", false);
        }
    }

    /**
     * Function to display simple Alert Dialog
     * @param context - application context
     * @param title - alert dialog title
     * @param message - alert message
     * @param status - success/failure (used to set icon)
     * */
    public void showAlertDialog(Context context, String title, String message, Boolean status) {
        AlertDialog alertDialog = new AlertDialog.Builder(context).create();

        // Setting Dialog Title
        alertDialog.setTitle(title);

        // Setting Dialog Message
        alertDialog.setMessage(message);

        // Setting alert dialog icon
        alertDialog.setIcon((status) ? R.drawable.success : R.drawable.fail);

        // Setting OK Button
        alertDialog.setButton("OK", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int which) {
            }
        });

        // Showing Alert Message
        alertDialog.show();
    }
}