Android

[{
        "id": 369,
        "guid": {
          "rendered": "URL?p=369"
        },
        "title": {
          "rendered": "Shudder"
        },
        "content": {
          "rendered": "<p>Shaking of body caused by fear.</p>\n<p>ভয়ের কাঁপুনি</p>\n<p> </p>\n",
          "protected": false
        },
        "post_categories": [
          "English",
          "Father's Help",
          "Madhyamik",
          "Prose",
          "Seen",
          "Word Nest"
        ]
      },
      {
        "id": 548,
        "guid": {
          "rendered": "URL?p=548"
        },
        "title": {
          "rendered": "Swami went ______ school feeling that he was ______ worst boy ______ earth."
        },
        "content": {
          "rendered": "<p>Swami went to school feeling that he was the worst boy on earth.</p>\n",
          "protected": false
        },
        "post_categories": [
          "Articles and Prepositions",
          "English",
          "Grammar",
          "Madhyamik"
        ]
      },
      {
        "id": 528,
        "guid": {
          "rendered": "URL?p=528"
        },
        "title": {
          "rendered": "Teacher said "Explain the law of gravitation"."
        },
        "content": {
          "rendered": "<p>Teacher ordered to explain the law of gravitation.</p>\n",
          "protected": false
        },
        "post_categories": [
          "English",
          "Grammar",
          "Madhyamik",
          "Narration"
        ]
      },
      {
        "id": 552,
        "guid": {
          "rendered": "URL?p=552"
        },
        "title": {
          "rendered": "Test Post "Image""
        },
        "content": {
          "rendered": "<p><img src=\"http://latex.codecogs.com/gif.latex?x^{2}+2xy+y^{2}&space;=&space;45\" alt=\"x^{2}+2xy+y^{2} = 45\" align=\"absmiddle\" /></p>\n<p> </p>\n<p><img src=\"http://aseducationsolution.com/wp-content/uploads/2018/06/blur-1868068_1920-150x150.jpg\" alt=\"\" width=\"150\" height=\"150\" class=\"alignnone wp-image-312 size-thumbnail\" /></p>\n<p> </p>\n<p>let us take  <img src=\"http://latex.codecogs.com/gif.latex?\\inline&space;\\fn_cm&space;\\small&space;\\left&space;(&space;a+b&space;\\right&space;)^{3}&space;+&space;\\alpha&space;\\lambda&space;\\varepsilon&space;\\Delta&space;ABC\" alt=\"\\inline \\fn_cm \\small \\left ( a+b \\right )^{3} + \\alpha \\lambda \\varepsilon \\Delta ABC\" align=\"absmiddle\" /></p>\n<p> </p>\n<p>another example  <img src=\"http://latex.codecogs.com/gif.latex?\\inline&space;\\small&space;a^{3}+b^{3}&space;=&space;123\" alt=\"\\inline \\small a^{3}+b^{3} = 123\" align=\"absmiddle\" />   check alignment is correct or not.</p>\n<p> </p>\n<p><img src=\"http://latex.codecogs.com/svg.latex?\\dpi{120}&space;\\small&space;\\frac{a}{b}+2c\" alt=\"\\dpi{120} \\small \\frac{a}{b}+2c\" align=\"absmiddle\" /> SVG</p>\n<p><img src=\"http://latex.codecogs.com/gif.latex?\\dpi{120}&space;\\small&space;\\sum&space;a+b+c+....\" alt=\"\\dpi{120} \\small \\sum a+b+c+....\" align=\"absmiddle\" /> GIF</p>\n<p> </p>\n<p>Equation example</p>\n<p> </p>\n<p> </p>\n",
          "protected": false
        },
        "post_categories": [
          "English",
          "Madhyamik"
        ]
      },
      {
        "id": 514,
        "guid": {
          "rendered": "URL?p=514"
        },
        "title": {
          "rendered": "Time when Swami complained of a headache _________?"
        },
        "content": {
          "rendered": "<p>9 A.M.</p>\n",
          "protected": false
        },
        "post_categories": [
          "English",
          "Father's Help",
          "Fill in from Text",
          "Madhyamik",
          "Prose",
          "Seen"
        ]
      }
    ]

{
      "code": "rest_post_invalid_page_number",
      "message": "The page number requested is larger than the number of pages available.",
      "data": {
        "status": 400
      }
    }

private RecyclerView recyclerView;
    private ProgressBar progressBar;
    private LinearLayoutManager mLayoutManager;
    private ArrayList < Model > list;
    private RecycleAdapter adapter;
    private View rootView;
    private int pageNo = 2;
    ProgressBar progress;
    public String url = RetrofitArrayAPI.baseURL + RetrofitArrayAPI.EngHomeKey;


    public static List < WPPost > mListPost;
    Boolean isScrolling = false;
    int currentItems, scrolledItems, totalItems;


    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {

      rootView = inflater.inflate(R.layout.search_englishhome, container, false);

      recyclerView = (RecyclerView) rootView.findViewById(R.id.postList);
      progressBar = (ProgressBar) rootView.findViewById(R.id.progressBar);
      mLayoutManager = new LinearLayoutManager(getActivity(), LinearLayoutManager.VERTICAL, false);
      recyclerView.setLayoutManager(mLayoutManager);
      DividerItemDecoration itemDecor = new DividerItemDecoration(Objects.requireNonNull(getActivity()), mLayoutManager.getOrientation());
      recyclerView.addItemDecoration(itemDecor);
      list = new ArrayList < > ();
      progress = (ProgressBar) rootView.findViewById(R.id.recyclerprogress);
      progress.setVisibility(View.GONE);
      adapter = new RecycleAdapter(list, getActivity());
      recyclerView.setAdapter(adapter);
      //Get Retrofit
      getRetrofit();
      recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {

        @Override
        public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
          super.onScrollStateChanged(recyclerView, newState);
          if (newState == AbsListView.OnScrollListener.SCROLL_STATE_TOUCH_SCROLL) {
            isScrolling = true;
          }
        }

        @Override
        public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
          super.onScrolled(recyclerView, dx, dy);
          currentItems = mLayoutManager.getChildCount();
          totalItems = mLayoutManager.getItemCount();
          scrolledItems = mLayoutManager.findFirstVisibleItemPosition();

          if (isScrolling = (currentItems + scrolledItems == totalItems)) {
            isScrolling = false;
            url = RetrofitArrayAPI.baseURL + RetrofitArrayAPI.EngHomeKey + "&page=" + pageNo;

            progress.setVisibility(View.VISIBLE);
            if (mListPost != null) {
              getRetrofit();
            } else {

              progress.setVisibility(View.GONE);
            }

          }

        }
      });

      return rootView;

    }


    public void getRetrofit() {

      final Retrofit retrofit = new Retrofit.Builder()
        .baseUrl(RetrofitArrayAPI.baseURL)
        .addConverterFactory(GsonConverterFactory.create())
        .build();

      RetrofitArrayAPI service = retrofit.create(RetrofitArrayAPI.class);


      final Call < List < WPPost >> call = service.getPostInfo(url);
      call.enqueue(new Callback < List < WPPost >> () {
        @Override
        public void onResponse(Call < List < WPPost >> call, Response < List < WPPost >> response) {


          Log.e("EnglishHome", "Response" + response.body());

          mListPost = response.body();
          progressBar.setVisibility(View.GONE);


          if (response.body() != null) {
            pageNo++;
            for (int i = 0; i < response.body().size(); i++) {
              String tempCode = response.body().get(i).getCode();
              int tempID = response.body().get(i).getId();
              String tempTitle = response.body().get(i).getTitle().getRendered();
              tempTitle = tempTitle.replace(""", "\"");
              tempTitle = tempTitle.replace(""", "\"");
              String tempContent = response.body().get(i).getContent().getRendered();
              List < String > catitemnames = response.body().get(i).getPostCategories();

              catitemnames.remove("Madhyamik");
              catitemnames.remove("English");
              catitemnames.remove("Grammar");
              catitemnames.remove("Seen");
              catitemnames.remove("Prose");
              catitemnames.remove("Poem");

              String categorynames = catitemnames.toString();
              categorynames = categorynames.substring(1, categorynames.length() - 1);
              if (tempCode != null) {
                response.body().clear();
                list.clear();
                isScrolling = false;
                mListPost.clear();
                return;
              } else {
                list.add(new Model(tempID, tempTitle, tempContent, categorynames));

              }

            }
            mListPost.clear();
            progress.setVisibility(View.GONE);

          } else {
            progress.setVisibility(View.GONE);
          }

        }

        @Override
        public void onFailure(Call < List < WPPost >> call, Throwable t) {

        }


      });

    }


    }

public class RecycleAdapter extends RecyclerView.Adapter {

      private ArrayList < Model > dataset;
      private Context mContext;

      public RecycleAdapter(ArrayList < Model > mList, Context context) {

        this.dataset = mList;
        this.mContext = context;

      }

      public static class ListTypeViewHolder extends RecyclerView.ViewHolder {


        TextView title, categories;
        RelativeLayout relativeLayout;


        ListTypeViewHolder(View itemView) {
          super(itemView);

          this.title = (TextView) itemView.findViewById(R.id.texttitlesofrv);
          this.categories = (TextView) itemView.findViewById(R.id.textcategoryrv);
          this.relativeLayout = (RelativeLayout) itemView.findViewById(R.id.recyclerrow);
        }
      }

      @NonNull
      @Override
      public RecyclerView.ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.recycler_item, parent, false);

        return new ListTypeViewHolder(view);
      }

      @Override
      public void onBindViewHolder(@NonNull final RecyclerView.ViewHolder holder, int position) {
        //holder.getAdapterPosition();
        final Model object = dataset.get(holder.getAdapterPosition());

        ((ListTypeViewHolder) holder).title.setText(object.title);
        ((ListTypeViewHolder) holder).categories.setText(object.categoriesnames);


        ((ListTypeViewHolder) holder).relativeLayout.setOnClickListener(new View.OnClickListener() {
          @Override
          public void onClick(View v) {

            Intent intent = new Intent(mContext, FullPostView.class);
            intent.putExtra("itemPosition", holder.getAdapterPosition());
            intent.putExtra("postID", object.postid);
            intent.putExtra("postTitle", object.title);
            intent.putExtra("postContent", object.content);

            mContext.startActivity(intent);
          }
        });



      }


      @Override
      public int getItemViewType(int position) {
        return position;
      }

      @Override
      public long getItemId(int position) {
        return position;
      }

      @Override
      public int getItemCount() {

        return dataset.size();
      }
    }

public class WPPost {

      @SerializedName("code")
      @Expose
      private String code;
      @SerializedName("id")
      @Expose
      private Integer id;
      @SerializedName("guid")
      @Expose
      private Guid guid;
      @SerializedName("title")
      @Expose
      private Title title;
      @SerializedName("content")
      @Expose
      private Content content;
      @SerializedName("post_categories")
      @Expose
      private List < String > postCategories = null;

      public Integer getId() {
        return id;
      }

      public void setId(Integer id) {
        this.id = id;
      }

      public Guid getGuid() {
        return guid;
      }

      public void setGuid(Guid guid) {
        this.guid = guid;
      }

      public Title getTitle() {
        return title;
      }

      public void setTitle(Title title) {
        this.title = title;
      }

      public Content getContent() {
        return content;
      }

      public void setContent(Content content) {
        this.content = content;
      }

      public List < String > getPostCategories() {
        return postCategories;
      }

      public void setPostCategories(List < String > postCategories) {
        this.postCategories = postCategories;
      }
      public String getCode() {
        return code;
      }

      public void setCode(String code) {
        this.code = code;
      }

    }

public class Model {

      public int postid;
      public String title;
      public String content;
      public String categoriesnames;


      public Model(int mID, String mTitle, String mContent, String mCategorynames) {

        this.postid = mID;
        this.title = mTitle;
        this.content = mContent;
        this.categoriesnames = mCategorynames;

      }

Quote:

Android Studio 3.0.1 Build #AI-171.4443003, built on November 9th, 2017
JRE: 1.8.0-152-release-915-b01 amd64
JVM: OpenJDK 64-Bit Server VM by JetBrains s.r.o
Windows 8.1 6.3

Quote:

I'm writing a program using bound service with Inter Process Communication(IPC). The goal is to send the generated data in a thread (DataExchange) from the service to the mainActivity, using Messenger and Hanler. When the data is placed in the message queue from run method, I'm unable to receive it in the activityHandler (mainActivity). fortunatly I can receive the data in the serviceHandler (Local communication), however when I try to send the same message from the serviceHandler (service) to activityHandler (mainActivity), I'm getting a FATAL EXCETION
java.lang.NullPointerException: Attempt to invoke virtual method 'void android.os.Messenger.send(android.os.Message)' on a null object reference
Someone please help

import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.content.ServiceConnection;
import android.os.Handler;
import android.os.IBinder;
import android.os.Message;
import android.os.Messenger;
import android.os.RemoteException;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {
    private static final String TAG = MainActivity.class.getSimpleName();
    private static final int UPDATE = 2;

    TextView textView;
    Messenger activityMessenger;
    boolean bound = false;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        textView = (TextView)findViewById(R. id. textView);

        Intent bindBtService = new Intent(this, BluetoothService.class);
        bindService(bindBtService, serviceConnection, Context.BIND_AUTO_CREATE);
    }

    private ServiceConnection serviceConnection = new ServiceConnection() {
        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            activityMessenger = new Messenger(service);
            bound = true;
        }

        @Override
        public void onServiceDisconnected(ComponentName name) {
            unbindService(serviceConnection);
            activityMessenger = null;
            bound = false;

        }
    };

    /*To process Incoming massages from the service*/
    class activityHandler extends Handler{
        @Override
        public void handleMessage(Message msg) {
            String received;
            switch (msg.what){
                case UPDATE:
                    received = msg.getData().getString("update");
                    //for debugging
                    Log.i(TAG, "From Run Method " + received);
                    textView.setText(received);
                    break;

                default:
                    super.handleMessage(msg);
            }
        }
    }

    @Override
    protected void onDestroy() {
        unbindService(serviceConnection);
        activityMessenger = null;
        bound = false;
        super.onDestroy();
    }
}

import android.app.Service;
import android.content.Intent;
import android.os.Bundle;
import android.os.Handler;
import android.os.IBinder;
import android.os.Looper;
import android.os.Message;
import android.os.Messenger;
import android.os.RemoteException;
import android.os.SystemClock;
import android.util.Log;

import java.util.Random;

public class BluetoothService extends Service {
    private  static final String TAG = BluetoothService.class.getSimpleName();
    private static final int SEND = 1;
    private static final int UPDATE = 2;

    private DataExchange dataExchange;

    //Messenger serviceMessenger;
    Messenger serviceMessenger = new Messenger(new ServiceHandler());
    public BluetoothService() {
        //Log.i(TAG, "Inside CONSTRUCTOR");
    }

    @Override
    public void onCreate() {
        super.onCreate();
        //Log.i(TAG, "Inside ONCREATE");
        //serviceMessenger = new Messenger(new ServiceHandler());

        //create a new thread with a serviceHandler object
        dataExchange = new DataExchange(new ServiceHandler());
        dataExchange.start();
    }

    /*Pass the binding object Messenger with a reference of the serviceHandler
     *to perform IPC communication
    */
    @Override
    public IBinder onBind(Intent intent) {
        return serviceMessenger.getBinder();
    }

    class ServiceHandler extends Handler{
        Messenger mess;
        Message message;
        String response = " ";
        Bundle bundle = new Bundle();

        @Override
        public void handleMessage(Message msg) {
            switch (msg.what){

                /*GET THE DATA FROM RUN METHOD AND SEND IT TO  mainActivity*/
                case SEND:
                    response = msg.getData().getString("message");
                    //Log for debug proposes
                    Log.i(TAG, "Random Number: " + response );
                    /*Initiate message object with a identifier*/
                    message = Message.obtain(null, UPDATE);
                    //Put the  and a keyword and the string message into a bundle
                    bundle.putString("update", response);
                    //Pass the bundle to the message object
                    message.setData(bundle);
                        try {
                            /* place the message into the message queue
                             * replyTo returns a reference from the receive Handler
                             * in this case the receive handler is the activityHandle
                            */
                           msg.replyTo.send(message);
                        } catch (RemoteException e) {
                            e.printStackTrace();
                        }
                        break;
                default:
                    super.handleMessage(msg);
            }
        }
    }

    private class DataExchange extends Thread implements Runnable{
        Handler serviceHandler;
        public DataExchange(ServiceHandler serviceHandler) {
            super();
            //new object of the handler class to process communication
            this.serviceHandler = serviceHandler;
        }

        @Override
        public void run() {

            for (int i = 0; i < 100; i++){
                String val = String.valueOf(i);

                try {
                    Thread.sleep(1000);
                    Message msg = prepareMessage(val);
                    //place message on the messageQueue
                    //serviceHandler.sendMessage(msg);

                    try {
                        serviceMessenger.send(msg);

                    } catch (RemoteException e) {
                        e.printStackTrace();
                    }

                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }

        /*prepare the message with a identifier, a key word and a string message
        * id : UPDATE and key word :update defines a message to be sent
        * to the mainActivity (Inter Process Communication "IPC")
        * id : SEND and key word :message defines a message to be sent
        * to the serviceHandler (Local communication)
        * */
        private Message prepareMessage(String string){

            Bundle dataBundle = new Bundle();

            /*For IPC communication*/
            //Message result = serviceHandler.obtainMessage(UPDATE);
            //dataBundle.putString("update", string);

            /*For LOCAL communication*/
            Message result = serviceHandler.obtainMessage(SEND);
            dataBundle.putString("message", string);
            //result.replyTo = new Messenger(new ServiceHandler());
            result.setData(dataBundle);

            return result;
        }
    }
}

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.seber.lisah">

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

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

        <service
            android:name=".BluetoothService"
            android:enabled="true"
            android:exported="true"></service>
    </application>

</manifest>