How to handle null pointer exception in android

Question

I am trying to make photo gallery application.But I am having following error and my program will crashed.Also I am having error to this line :

imageView.setImageResource(pics[arg2]);

error

09-03 16:45:22.618: E/AndroidRuntime(443): Uncaught handler: thread main exiting due to uncaught exception
09-03 16:45:22.628: E/AndroidRuntime(443): java.lang.NullPointerException
09-03 16:45:22.628: E/AndroidRuntime(443):  at com.example.myfirstapplication.setwall$1.onItemClick(setwall.java:40)
09-03 16:45:22.648: E/dalvikvm(443): Unable to open stack trace file '/data/anr/traces.txt': Permission denied

Here is my code:

package com.sai.samples.views;

import android.app.Activity;
import android.content.Context;
import android.content.res.TypedArray;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.BaseAdapter;
import android.widget.Gallery;
import android.widget.ImageView;
import android.widget.Toast;
import android.widget.AdapterView.OnItemClickListener;

public class GalleryView extends Activity {
    Integer[] pics = {
            R.drawable.antartica1,
            R.drawable.antartica2,
            R.drawable.antartica3,
            R.drawable.antartica4,
            R.drawable.antartica5,
            R.drawable.antartica6,
            R.drawable.antartica7,
            R.drawable.antartica8,
            R.drawable.antartica9,
            R.drawable.antartica10
    };
    ImageView imageView;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        Gallery ga = (Gallery)findViewById(R.id.Gallery01);
        ga.setAdapter(new ImageAdapter(this));

        imageView = (ImageView)findViewById(R.id.ImageView01);
        ga.setOnItemClickListener(new OnItemClickListener() {

            @Override
            public void onItemClick(AdapterView<?> arg0, View arg1, int arg2,
                    long arg3) {
                Toast.makeText(getBaseContext(), 
                        "You have selected picture " + (arg2+1) + " of Antartica", 
                        Toast.LENGTH_SHORT).show();
                imageView.setImageResource(pics[arg2]);

            }

        });

    }


    public class ImageAdapter extends BaseAdapter {

        private Context ctx;
        int imageBackground;

        public ImageAdapter(Context c) {
            ctx = c;
            TypedArray ta = obtainStyledAttributes(R.styleable.Gallery1);
            imageBackground = ta.getResourceId(R.styleable.Gallery1_android_galleryItemBackground, 1);
            ta.recycle();
        }

        @Override
        public int getCount() {

            return pics.length;
        }

        @Override
        public Object getItem(int arg0) {

            return arg0;
        }

        @Override
        public long getItemId(int arg0) {

            return arg0;
        }

        @Override
        public View getView(int arg0, View arg1, ViewGroup arg2) {
            ImageView iv = new ImageView(ctx);
            iv.setImageResource(pics[arg0]);
            iv.setScaleType(ImageView.ScaleType.FIT_XY);
            iv.setLayoutParams(new Gallery.LayoutParams(150,120));
            iv.setBackgroundResource(imageBackground);
            return iv;
        }

    }
}

here is my main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">

<Gallery 
    android:id="@+id/Gallery01" 
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content"></Gallery>
<ImageView 
    android:id="@+id/ImageView01" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content"></ImageView>

</LinearLayout>

did you tried to debug your code? ... imageView is null, i think ... — Selvin
– Selvin, Commented Sep 3, 2012 at 11:22
what is the line which logcat pointing onItemClick(setwall.java:40) — Anu
– Anu, Commented Sep 3, 2012 at 11:23
@kaluwila at imageView.setImageResource(pics[arg2]); this line I am having error. — Rash
– Rash, Commented Sep 4, 2012 at 6:22

Dalmas · Accepted Answer · 2012-09-03 11:23:59Z

7

This line probably returns null :

imageView = (ImageView)findViewById(R.id.ImageView01);

Check if the ImageView id is correct, and try to clean and rebuild your project if the error persists.

answered Sep 3, 2012 at 11:23

Dalmas

26.6k9 gold badges71 silver badges82 bronze badges

Sign up to request clarification or add additional context in comments.

8 Comments

Dalmas Over a year ago

Are you sure? The listener is added to the gallery, not the ImageView.

Rash Over a year ago

@Dalmas I dont understand what exactly you are saying.Please explain

Dalmas Over a year ago

I mean it's very likely that there isn't an ImageView with the id ImageView01 in your main.xml file.

Dalmas Over a year ago

Can you post your main.xml file?

Rash Over a year ago

@Dalmas I have posted the main.xml file

|

Sahil Mahajan Mj · Accepted Answer · 2012-09-03 11:45:16Z

1

I have used this code for creating a gallery of images,

public class GalleryViewActivity extends Activity 
{

    GridView gridView;
    @Override
    public void onCreate(Bundle savedInstanceState) 
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        gridView = (GridView)findViewById(R.id.gridView);

           gridView.setAdapter(new ImageAdapter(this));
    }
}


class ImageAdapter extends BaseAdapter 
{
    ArrayList<String> images;

    private Context mContext;

    public ImageAdapter(Context c) 
    {
        mContext = c;
    }

    public int getCount() 
    {
        return mThumbIds.length;
    }

    public Object getItem(int position) 
    {
        return null;
    }

    public long getItemId(int position) 
    {
        return 0;
    }

    // create a new ImageView for each item referenced by the Adapter
    public View getView(final int position, View convertView, ViewGroup parent) 
    {
        ImageView imageView;
        if (convertView == null)
        {  // if it's not recycled, initialize some attributes
            imageView = new ImageView(mContext);
            imageView.setLayoutParams(new GridView.LayoutParams(85, 85));
            imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
            imageView.setPadding(8, 8, 8, 8);
        }
        else 
        {
            imageView = (ImageView) convertView;
        }
           imageView.setClickable(true);

           imageView.setOnClickListener(new OnClickListener()
           {            
            @Override
            public void onClick(View v) 
            {
                Intent i = new Intent(v.getContext(), showImageClass.class);
                Toast.makeText(v.getContext(), mThumbIds.toString() + " Clicked", 5000).show();
                i.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                i.putExtra("imageName", mThumbIds[position]);
                v.getContext().startActivity(i);
            }
        });
//         imageView.setImageDrawable(images);
//         imageView.setImageBitmap(images);
//         imageView.setImageResource(images[]);
        imageView.setImageResource(mThumbIds[position]);
        return imageView;
    }

//     references to images
    private Integer[] mThumbIds = 
    {
            R.drawable.abc,
            R.drawable.def,
            R.drawable.klm, 
            R.drawable.pqr,
            R.drawable.rst, 
            R.drawable.wxy,
            R.drawable.xyz, 
    };
}

answered Sep 3, 2012 at 11:45

Sahil Mahajan Mj

11.2k8 gold badges56 silver badges101 bronze badges

4 Comments

Rash Over a year ago

I want to show all images in only that activity.In this code you have added showImageClass.So I dont want to do that.can you please change this code?

Sahil Mahajan Mj Over a year ago

Have you used this code. This code is to show gallery type view of Images, where all images are shown that are in drawable folder. showImage class is created to show large view of the image. whenever you click on any of the image from gallery view, 'showImage' class is called to show large view of the image clicked.

Rash Over a year ago

I am able to see gallery images only when I am clicking on it for showing large view it is stop working.

Sahil Mahajan Mj Over a year ago

I am posting my code for showing both the gallery view and the large image.

Sahil Mahajan Mj · Accepted Answer · 2012-09-04 05:56:41Z

First create a class GalleryViewActivity

public class GalleryViewActivity extends Activity 
{

    GridView gridView;
    @Override
    public void onCreate(Bundle savedInstanceState) 
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        gridView = (GridView)findViewById(R.id.gridView);
        gridView.setAdapter(new ImageAdapter(this));
    }
}


class ImageAdapter extends BaseAdapter 
{
    ArrayList<String> images;

    private Context mContext;

    public ImageAdapter(Context c) 
    {
        mContext = c;
    }

    public int getCount() 
    {
        return mThumbIds.length;
    }

    public Object getItem(int position) 
    {
        return null;
    }

    public long getItemId(int position) 
    {
        return 0;
    }

    // create a new ImageView for each item referenced by the Adapter
    public View getView(final int position, View convertView, ViewGroup parent) 
    {
        ImageView imageView;
        if (convertView == null)
        {  // if it's not recycled, initialize some attributes
            imageView = new ImageView(mContext);
            imageView.setLayoutParams(new GridView.LayoutParams(85, 85));
            imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
            imageView.setPadding(8, 8, 8, 8);
        }
        else 
        {
            imageView = (ImageView) convertView;
        }
           imageView.setClickable(true);

           imageView.setOnClickListener(new OnClickListener()
           {            
            @Override
            public void onClick(View v) 
            {
                Intent i = new Intent(v.getContext(), showImageClass.class);
                i.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                i.putExtra("position", "" + position);
                v.getContext().startActivity(i);
            }
        });
        imageView.setImageResource(mThumbIds[position]);
        return imageView;
    }

//     references to images
    private Integer[] mThumbIds = 
    {
            R.drawable.abc,
            R.drawable.def,
            R.drawable.klm, 
            R.drawable.pqr,
            R.drawable.rst, 
            R.drawable.wxy,
            R.drawable.xyz, 
    };
}

Dont forget to add images in the drawable folder. the image should be same as you mentioned in the mThumbIds array, like i have used abc.jpg, def.jpg and so on.. Then you need to create a showImage.java class, here you take a imageview to show the large view of image clicked..

public class showImageClass extends Activity
{
    private Integer[] mThumbIds = 
    {
            R.drawable.abc,
            R.drawable.def,
            R.drawable.klm, 
            R.drawable.pqr,
            R.drawable.rst, 
            R.drawable.wxy,
            R.drawable.xyz, 
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) 
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.showimage);
        int position = Integer.parseInt(this.getIntent().getStringExtra("position"));
        ImageView jpgView = (ImageView)findViewById(R.id.imageView);
        jpgView.setImageResource(mThumbIds[position]);
    }
}

This code has worked for me, it will definitely work.. Dont forget to add the relavent images and import the class libraries that are needed. Mention both the activities in android manifest file

Collectives™ on Stack Overflow

How to handle null pointer exception in android

3 Answers 3

8 Comments

4 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

8 Comments

4 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related