クラッシュする代わりにアプリに「Net not connected」メッセージを表示させるには

Question

アプリがクラッシュし、エラーが見つかりません。

ネットワークが接続されていないというメッセージを私に伝えたいと思います。

import java.io.BufferedReader; 
import java.io.IOException; 
import java.io.InputStream; 
import java.io.InputStreamReader; 
import java.io.UnsupportedEncodingException; 
import java.util.ArrayList; 
import java.util.List; 
import org.apache.http.HttpEntity; 
import org.apache.http.HttpResponse; 
import org.apache.http.NameValuePair; 
import org.apache.http.client.ClientProtocolException; 
import org.apache.http.client.HttpClient; 
import org.apache.http.client.entity.UrlEncodedFormEntity; 
import org.apache.http.client.methods.HttpPost; 
import org.apache.http.impl.client.DefaultHttpClient; 
import org.apache.http.message.BasicNameValuePair; 
import org.json.JSONException; 
import org.json.JSONObject; 
import android.app.Activity; 
import android.app.Dialog; 
import android.app.ProgressDialog; 
import android.content.Intent; 
import android.os.AsyncTask; 
import android.os.Bundle; 
import android.view.Menu; 
import android.view.MenuItem; 
import android.view.View; 
import android.widget.EditText; 
import android.widget.Toast; 


public class SimpleForm extends Activity { 

private EditText editTextUserName; 
private EditText editTextPassword; 

//public static final String USER_NAME = "USERNAME"; 

String username; 
String password; 


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

    editTextUserName = (EditText) findViewById(R.id.et_username_ID); 
    editTextPassword = (EditText) findViewById(R.id.et_pass_ID); 

} 

public void invokeLogin(View view){ 
    username = editTextUserName.getText().toString(); 
    password = editTextPassword.getText().toString(); 


    login(username,password); 

} 

private void login(final String username, String password) { 

    class LoginAsync extends AsyncTask<String, Void, String>{ 

     private Dialog loadingDialog; 

     @Override 
     protected void onPreExecute() { 
      super.onPreExecute(); 
      loadingDialog = ProgressDialog.show(SimpleForm .this, "Please wait", "Loading..."); 
     } 

     @Override 
     protected String doInBackground(String... params) { 
      //String uname = params[0]; 
      // String pass = params[1]; 


      JSONObject jsonObject = new JSONObject(); 
      try { 
       jsonObject.accumulate("username", params[0]); 
      } catch (JSONException e4) { 
       // TODO Auto-generated catch block 
       e4.printStackTrace(); 
      } 
      try { 
       jsonObject.accumulate("password", params[1]); 
      } catch (JSONException e3) { 
       // TODO Auto-generated catch block 
       e3.printStackTrace(); 
      } 
      try { 
       jsonObject.accumulate("deviceToken", "2324h5gj345gj3h4g5j"); 
      } catch (JSONException e5) { 
       // TODO Auto-generated catch block 
       e5.printStackTrace(); 
      } 
      try { 
       jsonObject.accumulate("os", "android"); 
      } catch (JSONException e2) { 
       // TODO Auto-generated catch block 
       e2.printStackTrace(); 
      } 
      try { 
       jsonObject.accumulate("key", "MEu07MgiuWgXwJOo7Oe1aHL0yM8P"); 
      } catch (JSONException e1) { 
       // TODO Auto-generated catch block 
       e1.printStackTrace(); 
      } 


      // 4. convert JSONObject to JSON to String 
      String dataString = jsonObject.toString(); 



      //String dataString = {"username":"apitest","password":"123456","deviceToken":"2324h5gj345gj3h4g5j34g","os":"andriod","key":"MEu07MgiuWgXwJOo7Oe1aHL0yM8VvP"} 
      InputStream is = null; 
      List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>(); 
      nameValuePairs.add(new BasicNameValuePair("data", dataString)); 
      //nameValuePairs.add(new BasicNameValuePair("password", pass)); 
      String result = null; 

      try{ 
       HttpClient httpClient = new DefaultHttpClient(); 
       HttpPost httpPost = new HttpPost(
         "http://mobile.betfan.com/api/?action=login"); 
       //http://mobile.betfan.com/api/?action=login 
       //http://192.168.1.10/mobiletest/process.php 
       httpPost.setEntity(new UrlEncodedFormEntity(nameValuePairs)); 

       HttpResponse response = httpClient.execute(httpPost); 

       HttpEntity entity = response.getEntity(); 

       is = entity.getContent(); 

       BufferedReader reader = new BufferedReader(new InputStreamReader(is, "UTF-8"), 8); 
       StringBuilder sb = new StringBuilder(); 

       String line = null; 
       while ((line = reader.readLine()) != null) 
       { 
        sb.append(line + "\n"); 
       } 
       result = sb.toString(); 
      } catch (ClientProtocolException e) { 
       e.printStackTrace(); 
      } catch (UnsupportedEncodingException e) { 
       e.printStackTrace(); 
      } catch (IOException e) { 
       e.printStackTrace(); 
      } 
      return result; 
     } 

     protected void onPostExecute(String result){ 
      String s = result.trim(); 
      loadingDialog.dismiss(); 

       JSONObject respObject; 
       try { 
        respObject = new JSONObject(s); 
        String active = respObject.getString("status_message"); 

        if(active.equalsIgnoreCase("success")){ 
         Toast.makeText(getApplicationContext(), s+"Login successfull", Toast.LENGTH_LONG).show(); 

         Intent intent=new Intent(SimpleForm.this,Welcome.class); 
         startActivity(intent); 
         // Intent intent = new Intent(MainActivity.this, UserProfile.class); 
         //intent.putExtra(USER_NAME, username); 
         // finish(); 
         //startActivity(intent); 
        }else { 
         Toast.makeText(getApplicationContext(), "Login Fail", Toast.LENGTH_LONG).show(); 

        } 

       } catch (JSONException e) { 
        // TODO Auto-generated catch block 
        e.printStackTrace(); 
       } 



     } 
    } 

    LoginAsync la = new LoginAsync(); 
    la.execute(username, password); 

} 


@Override 
public boolean onCreateOptionsMenu(Menu menu) { 
    // Inflate the menu; this adds items to the action bar if it is present. 
    getMenuInflater().inflate(R.menu.main, menu); 
    return true; 
} 

@Override 
public boolean onOptionsItemSelected(MenuItem item) { 
    // Handle action bar item clicks here. The action bar will 
    // automatically handle clicks on the Home/Up button, so long 
    // as you specify a parent activity in AndroidManifest.xml. 
    int id = item.getItemId(); 

    //noinspection SimplifiableIfStatement 
    if (id == R.id.action_settings) { 
     return true; 
    } 

     return super.onOptionsItemSelected(item); 
    } 
    } 

Answer 1

あなたがネットワーク接続を必要とするすべてのコードを使用する前に、あなたが接続を確認するために、このようなメソッドを呼び出すことができます。

private boolean isConnected() { 
    ConnectivityManager connectivityManager = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE); 
    NetworkInfo networkInfo = connectivityManager.getActiveNetworkInfo(); 
    return networkInfo != null && networkInfo.isConnectedOrConnecting(); 
}