我在哪里应该在Android中调用Interface？

Question

I am trying to call the activity method from the adaptor class using interface. And both the activity are independent ie class which is calling adapter and the class where the method is defined.

Interface class

public interface AdapterCallback  {        
    int onMethodCallback();
}

Adapter class

public class SimpleAdapter extends RecyclerView.Adapter<SimpleAdapter.ViewHolder> {

    String[] goals;
    Context context;
    private AdapterCallback mAdapterCallback;


    public  SimpleAdapter(Context context, String[] goals)
    {
        super();
        this.context=context;
        this.goals=goals;


    }

   /* public SimpleAdapter(Context context) {

        try {

        } catch (ClassCastException e) {
            throw new ClassCastException("Activity must implement AdapterCallback.");
        }

    }*/

    @Override
    public SimpleAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {

        View view= LayoutInflater.from(parent.getContext()).inflate(R.layout.simple_item,parent,false);
        return new ViewHolder(view);
    }

    @Override
    public void onBindViewHolder(final SimpleAdapter.ViewHolder holder, int position) {

      holder.textView.setText(goals[position]);

      holder.textView.setOnClickListener(new View.OnClickListener() {
          @Override
          public void onClick(View view) {

              try {
                  mAdapterCallback = ((AdapterCallback) context);
                  int result=mAdapterCallback.onMethodCallback();
                  Toast.makeText(context,Integer.toString(result), Toast.LENGTH_SHORT).show();
              } catch (ClassCastException exception) {
                  // do something
                  Log.i("In the catch","Yes");
              }




          }
      });

    }

    @Override
    public int getItemCount() {
        return  goals.length;
    }


    public class ViewHolder extends RecyclerView.ViewHolder {

        Button textView;

        public ViewHolder(View itemView) {
            super(itemView);

            textView=(Button) itemView.findViewById(R.id.text);
        }
    }

}

Method is defined in the MainActivity.class

@Override
public int onMethodCallback() {
    // do something
    return 2;
}

Problem: How should I call the interface function so that indirectly it will call the function defined in the MainActivity class.

I know I need to provide the context of the MainActivity as

mAdapterCallback = ((AdapterCallback) context);

but where should I put this code.

IF i put this code in the constructor then it will not get the MainActivity class context because adapter is calling from another class.

EDIT:

public class MainActivity extends AppCompatActivity implements AdapterCallback {


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

        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                        .setAction("Action", null).show();
            }
        });
    }

    @Override
    public int onMethodCallback() {
        // do something
        return 2;
    }


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


    public int sampleFunction()
    {
        return 2;
    }
}

EDIT 2

Class which is calling the adaptor class

public class OtherClass extends AppCompatActivity {

    RecyclerView recyclerView;
    SimpleAdapter simpleAdapter;
    String[]  action_name={"Swimming","Yoga","SWD","IFT","Follow Diet Plan", "Diagnostic Tests","Record Temperature","Record Blood Pressure"," Record Sugar Level","Record Weight"};

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

        recyclerView=(RecyclerView) findViewById(R.id.recylerview);
        recyclerView.setHasFixedSize(true);
        recyclerView.setLayoutManager(new LinearLayoutManager(this));


        simpleAdapter=new SimpleAdapter(this, action_name);

        recyclerView.setAdapter(simpleAdapter);

    }
}

Answer 1

   public class SimpleAdapter extends RecyclerView.Adapter<SimpleAdapter.ViewHolder> {

    String[] goals;
    Context context;
    private AdapterCallback mAdapterCallback;


    public  SimpleAdapter(Context context, String[] goals)
    {
        super();
        this.context=context;
        this.goals=goals;
    }

   /* public SimpleAdapter(Context context) {

        try {

        } catch (ClassCastException e) {
            throw new ClassCastException("Activity must implement AdapterCallback.");
        }

    }*/

    @Override
    public SimpleAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {

        View view= LayoutInflater.from(parent.getContext()).inflate(R.layout.simple_item,parent,false);
        return new ViewHolder(view);
    }

    @Override
    public void onBindViewHolder(final SimpleAdapter.ViewHolder holder, int position) {

        holder.textView.setText(goals[position]);

        holder.textView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {

                try {
                    mAdapterCallback = ((AdapterCallback) context);
                    int result=mAdapterCallback.onMethodCallback();
                    Toast.makeText(context,Integer.toString(result), Toast.LENGTH_SHORT).show();
                } catch (ClassCastException exception) {
                    // do something
                    Log.i("In the catch","Yes");
                }
            }
        });

    }
    @Override
    public int getItemCount() {
        return  goals.length;
    }

    public class ViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
        Button textView;
        public ViewHolder(View itemView) {
            super(itemView);
            textView=(Button) itemView.findViewById(R.id.text);
            //for entire cell
            itemView.setOnClickListener(this);
            //or only for button
            textView.setOnClickListener(this);
        }

        @Override
        public void onClick(View view) {
            /*
            If your want clicked position you can use bellow code
             */
            //int clicked_position = getAdapterPosition();
            mAdapterCallback.onMethodCallback(clicked_position,goals[clicked_position]);
        }
    }
}

this is the way we have to use interface in android recyclerview

Edits

change your interface like bellow

public interface AdapterCallback  {
    void onMethodCallback(int position,String value);
}

and on your OtherClass.class like bellow

    public class OtherClass extends AppCompatActivity implements AdapterCallback{

    RecyclerView recyclerView;
    SimpleAdapter simpleAdapter;
    String[]  action_name={"Swimming","Yoga","SWD","IFT","Follow Diet Plan", "Diagnostic Tests","Record Temperature","Record Blood Pressure"," Record Sugar Level","Record Weight"};

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

        recyclerView=(RecyclerView) findViewById(R.id.recylerview);
        recyclerView.setHasFixedSize(true);
        recyclerView.setLayoutManager(new LinearLayoutManager(this));


        simpleAdapter=new SimpleAdapter(this, action_name);

        recyclerView.setAdapter(simpleAdapter);

    }

    @Override
    public void onMethodCallback(int position, String value) {
        System.out.println(value+"    "+position);
        //start activity intent here , now you have position as well as selected value
    }
}

Answer 2

If you have implemented interface AdapterCallback in MainActivity then call constructor of SimpleAdapter with including a new paramenter of AdapterCallback Object. Try with these change. It may helps you

String[] goals;
Context context;
private AdapterCallback mAdapterCallback;

public  SimpleAdapter(Context context, AdapterCallback adapterCallback, String[] goals){
        super();
        this.context=context;
        this.adapterCallback = adapterCallback;
        this.goals=goals;
    }

and remove this

mAdapterCallback = ((AdapterCallback) context);

Answer 3

First you have set the interface.Write a method like this in your adapter class

    AdapterCallback  adapterCallback ;
    public void setAdapterCallback(AdapterCallback adapterCallback){
      this.adapterCallback = adapterCallback
    } 

Now impliment and initialize the interface where you actually requires the callback. In your case MainActivity Do like this

MainActivity extends AppCompatActivity implements AdapterCallback 

now initialize your interface like this.

   SimpleAdapter adpter = new SimpleAdapter()   
   adpter.setAdapterCallback(this);       // very imp step

Now send the callback like this

 holder.textView.setOnClickListener(new View.OnClickListener() {
          @Override
          public void onClick(View view) {
               if(adapterCallback  != null){
                  adapterCallback.onMethodCallback();  
              }
          }
      });

That's all you will get callback on your mainactivity..

Edit

I see you have your adapter set in another activity ..In that case you have to pass your interface object like this

AdapterCallback  adapterCallback = this;
Intent intent = new Intent(context, OtherClass.class);
intent.putExtra("interface", adapterCallback);
startActivity(intent);

And retreive it in OtherClass;

Intent intent = getIntent();
AdapterCallback   inter = (AdapterCallback) intent.getSerializableExtra("interface");

Also change interface to serializable .

public interface AdapterCallback  extends Serializable {
     int onMethodCallback();
}

And setInterface like this

  simpleAdapter.setAdapterCallback(inter);

If you jsut used a fragment instead of otherclass it would have been a lot easier..

Edit

If both activities are independent then you can write a gettter and setter for your interface in Application class. Set the interface from mainActivity and get the callback in your adater..
write this in your Application class

AdapterCallback  adapterCallback;
public AdapterCallback getAdapterCallback() {
    return adapterCallback;
}

public void setAdapterCallback(AdapterCallback adapterCallback) {
    this.adapterCallback = adapterCallback;
}

Write this in your Main

((YourApplication)getApplication()). setAdapterCallback(this);

And use this method in your click

((YourApplication) getApplication()).getAdapterCallback().onMethodCallback();

Answer 4

I'm not sure just a work around try,

If u have an Util class create a method or Create a Util class and do

say

 private Context mContext;
    public void setContext(Context context) {
        mContext = context;
    }

    public Context getContext(){

        return mContext;
    }

Then

set the context in MainActivity

like

Util.setContext(MainActivity.this);

and in SimpleAdapter class use Util.getContext() and

Context context = Util.getContext();
 if(context != null && context instanceof MainActivity){
    mAdapterCallback = ((AdapterCallback) context);
    int result=mAdapterCallback.onMethodCallback();
 }