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i've read all the similar question but i've problem with my arraylist...i didn't find a solution. i'm try to pass the data from my array list into my third activity to see fullscren images of the pages of the comic book.I get nullpointerexeption.

this is the code of my third activity:

package com.example.android.glidegalleryevilsecret;


import android.content.Intent;
import android.graphics.Matrix;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.Toolbar;
import android.view.MenuItem;
import android.view.MotionEvent;
import android.view.ScaleGestureDetector;
import android.widget.ImageView;
import android.widget.Toast;

public class PageActivity extends AppCompatActivity {

Toolbar toolbar;
Matrix matrix = new Matrix();
Float scale = 1f;
ScaleGestureDetector SGD;
private ImageView img;

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

    toolbar = findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    if (getSupportActionBar() != null) {
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
        getSupportActionBar().setDisplayShowHomeEnabled(true);
    }

    //receive data
    Intent intent = getIntent();
    int image = intent.getExtras().getInt("Thumbnail");

    //set value
    img.setImageResource(image);
    img = findViewById(R.id.pageImage);

    img.setOnTouchListener(new OnSwipeTouchListener(PageActivity.this) {
        public void onSwipeTop() {
            Toast.makeText(PageActivity.this, "top", Toast.LENGTH_SHORT).show();
        }

        public void onSwipeRight() {
            Toast.makeText(PageActivity.this, "right", Toast.LENGTH_SHORT).show();
        }

        public void onSwipeLeft() {
            Toast.makeText(PageActivity.this, "left", Toast.LENGTH_SHORT).show();
        }

        public void onSwipeBottom() {
            Toast.makeText(PageActivity.this, "bottom", Toast.LENGTH_SHORT).show();
        }

    });

    SGD = new ScaleGestureDetector(this, new ScaleListener());
}

@Override
public boolean onTouchEvent(MotionEvent event) {
    SGD.onTouchEvent(event);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    if (item.getItemId() == android.R.id.home)
        finish();
    return super.onOptionsItemSelected(item);
}

private class ScaleListener extends ScaleGestureDetector.SimpleOnScaleGestureListener {
    @Override
    public boolean onScale(ScaleGestureDetector detector) {
        scale = scale * detector.getScaleFactor();
        scale = Math.max(0.1f, Math.min(scale, 5f));
        matrix.setScale(scale, scale);
        img.setImageMatrix(matrix);
        return true;
    }
  }
}

Since i'm using recycler view i made a recycler adapter and here i put the intent that will pass the data to the third activity:

  package com.example.android.glidegalleryevilsecret;

  import android.content.Context;
  import android.content.Intent;
  import android.support.annotation.NonNull;
  import android.support.v7.widget.CardView;
  import android.support.v7.widget.RecyclerView;
  import android.view.LayoutInflater;
  import android.view.View;
  import android.view.ViewGroup;
  import android.widget.ImageView;
  import android.widget.TextView;

  import com.bumptech.glide.Glide;

  import java.util.List;

  public class RecyclerAdapter extends 
  RecyclerView.Adapter<RecyclerAdapter.MyViewHolder>{


    private Context mContext;
    private List<Page> mData;

    public RecyclerAdapter(Context mContext, List<Page> mData) {
        this.mContext = mContext;
        this.mData = mData;
    }


    @NonNull
    @Override
    public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int 
    viewType) {

        View view;
        LayoutInflater mInflater = LayoutInflater.from(mContext);
        view = mInflater.inflate(R.layout.cardview, parent,false);
        return new MyViewHolder(view);
    }

    @Override
    public void onBindViewHolder(@NonNull MyViewHolder holder, final int 
    position) {

        Glide.with(mContext)
                .load(mData.get(position).getThumbnail())
                .into(holder.page_thumbnail);


        holder.number_page.setText(mData.get(position).getNumberPage());
        holder.cardView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent (mContext, PageActivity.class);

                //passing data to the page activity
                intent.putExtra("Thumbnail", 
                mData.get(position).getThumbnail());
                //start the page activity
                mContext.startActivity(intent);
            }
        });

    }

    @Override
    public int getItemCount() {
        return mData.size();
    }

    public  static class MyViewHolder extends RecyclerView.ViewHolder {

        TextView number_page;
        ImageView page_thumbnail;
        CardView cardView;

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

            number_page = itemView.findViewById(R.id.number_page_id);
            page_thumbnail = itemView.findViewById(R.id.page_image_id);
            cardView = itemView.findViewById(R.id.cardView_id);
        }
    }

}

this is the second activity were is my entire array list:

  package com.example.android.glidegalleryevilsecret;

  import android.support.v7.app.AppCompatActivity;
  import android.os.Bundle;
  import android.support.v7.widget.GridLayoutManager;
  import android.support.v7.widget.RecyclerView;
  import android.view.MenuItem;
  import android.support.v7.widget.Toolbar;

  import java.util.ArrayList;

  public class SecondActivity extends AppCompatActivity {

Toolbar toolbar;

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

    toolbar = findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    if (getSupportActionBar()!=null){
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
        getSupportActionBar().setDisplayShowHomeEnabled(true);
    }

    ArrayList<Page> Page= new ArrayList<>();
    Page.add(new Page(R.drawable.prologo1,"Prologue 1"));
    Page.add(new Page(R.drawable.prologo2,"Prologue 2"));
    Page.add(new Page(R.drawable.prologo3,"Prologue 3"));
    Page.add(new Page(R.drawable.prologo4,"Prologue 4"));
    Page.add(new Page(R.drawable.prologo5,"Prologue 5"));
    Page.add(new Page(R.drawable.prologo6,"Prologue 6"));
    Page.add(new Page(R.drawable.pagina7,"Page 7"));
    Page.add(new Page(R.drawable.pagina8,"Page 8"));
    Page.add(new Page(R.drawable.pagina9,"Page 9"));
    Page.add(new Page(R.drawable.pagina10,"Page 10"));
    Page.add(new Page(R.drawable.pagina11,"Page 11"));
    Page.add(new Page(R.drawable.pagina12,"Page 12"));
    Page.add(new Page(R.drawable.pagina13,"Page 13"));
    Page.add(new Page(R.drawable.pagina14,"Page 14"));
    Page.add(new Page(R.drawable.pagina15,"Page 15"));
    Page.add(new Page(R.drawable.pagina16,"Page 16"));
    Page.add(new Page(R.drawable.pagina17,"Page 17"));
    Page.add(new Page(R.drawable.pagina18,"Page 18"));
    Page.add(new Page(R.drawable.pagina19,"Page 19"));
    Page.add(new Page(R.drawable.pagina20,"Page 20"));
    Page.add(new Page(R.drawable.pagina21,"Page 21"));
    Page.add(new Page(R.drawable.pagina22,"Page 22"));
    Page.add(new Page(R.drawable.pagina23,"Page 23"));
    Page.add(new Page(R.drawable.pagina24,"Page 24"));
    Page.add(new Page(R.drawable.pagina25,"Page 25"));
    Page.add(new Page(R.drawable.pagina26,"Page 26"));
    Page.add(new Page(R.drawable.pagina27,"Page 27"));
    Page.add(new Page(R.drawable.pagina28,"Page 28"));
    Page.add(new Page(R.drawable.pagina29,"Page 29"));
    Page.add(new Page(R.drawable.pagina30,"Page 30"));
    Page.add(new Page(R.drawable.pagina31,"Page 31"));
    Page.add(new Page(R.drawable.pagina32,"Page 32"));
    Page.add(new Page(R.drawable.pagina33,"Page 33"));
    Page.add(new Page(R.drawable.pagina34,"Page 34"));
    Page.add(new Page(R.drawable.pagina35,"Page 35"));
    Page.add(new Page(R.drawable.pagina36,"Page 36"));
    Page.add(new Page(R.drawable.pagina37,"Page 37"));
    Page.add(new Page(R.drawable.pagina38,"Page 38"));
    Page.add(new Page(R.drawable.pagina39,"Page 39"));
    Page.add(new Page(R.drawable.pagina40,"Page 40"));
    Page.add(new Page(R.drawable.pagina41,"Page 41"));
    Page.add(new Page(R.drawable.pagina42,"Page 42"));
    Page.add(new Page(R.drawable.pagina43,"Page 43"));
    Page.add(new Page(R.drawable.pagina44,"Page 44"));
    Page.add(new Page(R.drawable.pagina45,"Page 45"));
    Page.add(new Page(R.drawable.pagina46,"Page 46"));
    Page.add(new Page(R.drawable.pagina47,"Page 47"));
    Page.add(new Page(R.drawable.pagina48,"Page 48"));
    Page.add(new Page(R.drawable.pagina49,"Page 49"));
    Page.add(new Page(R.drawable.pagina50,"Page 50"));
    Page.add(new Page(R.drawable.pagina51,"Page 51"));
    Page.add(new Page(R.drawable.pagina52,"Page 52"));
    Page.add(new Page(R.drawable.pagina53,"Page 53"));
    Page.add(new Page(R.drawable.pagina54,"Page 54"));
    Page.add(new Page(R.drawable.pagina55,"Page 55"));
    Page.add(new Page(R.drawable.pagina56,"Page 56"));
    Page.add(new Page(R.drawable.pagina57,"Page 57"));
    Page.add(new Page(R.drawable.pagina58,"Page 58"));
    Page.add(new Page(R.drawable.pagina59,"Page 59"));
    Page.add(new Page(R.drawable.pagina60,"Page 60"));
    Page.add(new Page(R.drawable.pagina61,"Page 61"));
    Page.add(new Page(R.drawable.pagina62,"Page 62"));
    Page.add(new Page(R.drawable.pagina63,"Page 63"));
    Page.add(new Page(R.drawable.pagina64,"Page 64"));

    RecyclerView MyRV = findViewById(R.id.recyclerView_id);
    RecyclerAdapter MyAdapter = new RecyclerAdapter(this, Page);
    MyRV.setLayoutManager(new GridLayoutManager(this, 3));
    MyRV.setAdapter(MyAdapter);

}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
    if (item.getItemId()==android.R.id.home)
        finish();
    return super.onOptionsItemSelected(item);
 }
 }
Phantômaxx
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Simone Atzeni
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1 Answers1

2

This is because you are setting the image resource Before binding the view.

Try to reverse the order:

img = findViewById(R.id.pageImage);
img.setImageResource(image);
Fran Dioniz
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