Handling an Activity when non JSON data/Empty data is recieved with Alert or Custom Message

Question

I followed this to Read JSON data in android

over there I am passing result data to another activity

public class MainAct1 extends Activity {

private static String urlString;

private static final String My_TAG= "Log Status";

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setRequestedOrientation (ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
    setContentView(R.layout.data);

    if(Dcon.isInternetAvailable(this))
    {
        try {
            urlString = "https://example.net/api_json";
            new ProcessJSON(this).execute();
        }

        catch (Exception e) {
            AlertDialog.Builder builder = new AlertDialog.Builder(MainAct1.this);
            builder.setMessage("Note: Your Server ID is Invalid \n Please check the Server Status");
            builder.setTitle("Please Check Server Details");
            builder.setPositiveButton("OK",null);

            builder.setPositiveButton("OK", new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int which) {
                    dialog.dismiss();
                    finish();
                }
            });
            AlertDialog dialog = builder.create();
            dialog.show();
        }

    }
    else
    {
        AlertDialog alertDialog = new AlertDialog.Builder(MainAct1.this).create();
        alertDialog.setTitle("Connection Error !");
        alertDialog.setMessage("Internet not available, Check your internet connectivity and try again");

        alertDialog.setButton("OK", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int which) {
                android.os.Process.killProcess(android.os.Process.myPid());
                System.exit(1);
                finish();
            }
        });
        alertDialog.show();
    }

}

private class ProcessJSON extends AsyncTask<Void, Void, Void> {

    public Context context;
    String FinalJSonResult;

    public ProcessJSON(Context context) {
        this.context = context;
    }

    @Override
    protected void onPreExecute() {
        super.onPreExecute();

    }

    @Override
    protected Void doInBackground(Void... arg0) {
    HttpHandler sh = new HttpHandler(urlString);

        try {
            sh.ExecutePostRequest();
            if (sh.getResponseCode() == 200) {
                FinalJSonResult = sh.getResponse();
                if (FinalJSonResult != null) {
                    try {
                        JSONObject JObject = new JSONObject(FinalJSonResult);
                        JSONObject response = JObject.getJSONObject("response");

                     if(response.has("status")) {

                        String status = response.getString("status");
                            MainAct1.this.finish();
                            Intent op = new Intent(MainAct1.this, MainRes1.class);
                            op.putExtra("mydata", status);
                            op.setFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT);
                            op.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                            op.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK);
                            op.setFlags(Intent.FLAG_ACTIVITY_NO_ANIMATION);
                            startActivity(op);
                        }
                        else {
                                Toast.makeText(context, "No JSON data", Toast.LENGTH_SHORT).show();
                                AlertDialog alertDialog = new AlertDialog.Builder(NSdata.this).create();
                                alertDialog.setTitle("Server Error !");
                                alertDialog.setMessage("No Data Received");
                                alertDialog.setButton("OK", new DialogInterface.OnClickListener() {
                                    public void onClick(DialogInterface dialog, int which) {
                                        android.os.Process.killProcess(android.os.Process.myPid());
                                        System.exit(1);
                                        finish();
                                    }
                                });
                                alertDialog.show();
                            }
                    }
                    catch (JSONException e) {

                        AlertDialog.Builder builder = new AlertDialog.Builder(MainAct1.this);
                        builder.setMessage("Note: Your Server ID is Invalid \n Please check the Server Status");
                        builder.setTitle("Please Check Server Details");
                        builder.setPositiveButton("OK",null);

                        builder.setPositiveButton("OK", new DialogInterface.OnClickListener() {
                            @Override
                            public void onClick(DialogInterface dialog, int which) {
                                dialog.dismiss();
                                finish();
                            }
                        });
                        AlertDialog dialog = builder.create();
                        dialog.show();
                    }
                    catch (JSONException e) {

                    }
                }
                else{
                    AlertDialog alertDialog = new AlertDialog.Builder(MainAct1.this).create();
                    alertDialog.setTitle("User Error !");
                    alertDialog.setMessage("No Data Received");
                    alertDialog.setButton("OK", new DialogInterface.OnClickListener() {
                        public void onClick(DialogInterface dialog, int which) {
                            android.os.Process.killProcess(android.os.Process.myPid());
                            System.exit(1);
                            finish();
                        }
                    });
                    alertDialog.show();
                }
            }
            else {
                Toast.makeText(context, sh.getErrorMessage(), Toast.LENGTH_SHORT).show();
            }
        }
        catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }
}
@Override
public void onBackPressed() {
    moveTaskToBack(false);
    Toast.makeText(this, "Please wait for a While.. Don't Go back .!", Toast.LENGTH_SHORT).show();

}
}

this is my JSON Data

{"response":{"status":"Active"}}

or

{"response":{"status":"Active:4 in stock"}}

So now I am facing issue with

1.NonJSON some times json data is not received due to server error

or it will show Just some HTML headings...

I need to data Handle it Can any one suggest me.. on this kind

and

2.Empty JSON Data Some times Result may be Null like

{"response":{"status":""}}

or

{"response":{}}

Can Any Suggest me How to Handle those Kinds I already Given Alerts But its not working.

Now I am handling these two kinds of data but Some times I am getting Empty

Update

For a valid JSON data Its Showing Result in next Activity/page in a Text View...

Valid JSON data {"response":{"status":"Active"}} or {"response":{"status":"Please set the data."}}

I am showing Result... in Next Page

But Sometimes I will get Invalid JSON data like {"response":{"status":}} or Just HTML page with Welcome text... or OOps page not found ...

So I want to Handle them,,, if I get Invalid JSON Data I want to SHOW the Alert to the USER.... so that's what I am trying But its not working Please Help me on this types

Answer 1

JSONObject JObject = new JSONObject(FinalJSonResult); 
JSONObject response = JObject.getJSONObject("response");  

       // Check Key found or Not
    if(response.has("status")) {

                String status = response.getString("status");

                   // Check if Status Empty or Not
                   if(status.isEmpty()){

                   }

     } else {
            //Status Key not found
     }

• DoInBackground() only gets executed on a different thread other than the main UI thread.
• So you need to write AlertDialog in onPostExecute.
• In ProcessJSON class use FinalJSonResult string to handle different situation in onPostExecute().

ProcessJSON Class

private class ProcessJSON extends AsyncTask<Void, Void, Void> {

    public Context context;
    String FinalJSonResult;

    public ProcessJSON(Context context) {
        this.context = context;
    }

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        FinalJSonResult = "";
    }

    @Override
    protected Void doInBackground(Void... arg0) {
        HttpHandler sh = new HttpHandler(urlString);

        try {
            sh.ExecutePostRequest();
            if (sh.getResponseCode() == 200) {
                FinalJSonResult = sh.getResponse();
                if (FinalJSonResult != null) {
                    try {
                        JSONObject JObject = new JSONObject(FinalJSonResult);
                        JSONObject response = JObject.getJSONObject("response");

                        if(response.has("status")) {

                            String status = response.getString("status");
                            MainAct1.this.finish();
                            Intent op = new Intent(MainAct1.this, MainRes1.class);
                            op.putExtra("mydata", status);
                            op.setFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT);
                            op.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                            op.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK);
                            op.setFlags(Intent.FLAG_ACTIVITY_NO_ANIMATION);
                            startActivity(op);
                        }
                        else {
                            FinalJSonResult = "No JSON data";
                        }
                    }
                    catch (JSONException e) {

                        FinalJSonResult = "Your Server ID is Invalid";

                    }

                }
                else{

                    FinalJSonResult = "User Error";

                }
            }
            else {
                Toast.makeText(context, sh.getErrorMessage(), Toast.LENGTH_SHORT).show();
            }
        }
        catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

    @Override
    protected void onPostExecute(Void aVoid) {
        super.onPostExecute(aVoid);

        if(FinalJSonResult.equalsIgnoreCase("No JSON data")){

            // Your AlertDialog code....

        }else if(FinalJSonResult.equalsIgnoreCase("Your Server ID is Invalid")){

            // Your AlertDialog code....

        }else if(FinalJSonResult.equalsIgnoreCase("User Error")){

            // Your AlertDialog code....

        }


    }
}

Answer 2

Please try this

if(response.has("status")) {
        // Key found in Response JsonObject
        String status = response.getString("status");
    } else {
        //Status Key not found in Response JsonObject
    }

Answer 3

I recommend use library like Gson. and through try/catch & JsonSyntaxException will validate data. but original reason of bug is shape of data. rewrite shape of json data in serverside.