getpixel()is showing error

Question

i am using an image view in which i want to know the pixel color so i am using getpixel()... method but it is showing me an error .... this is the way i am using get pixel method..

image  = BitmapFactory.decodeResource(getResources(), rid);
                pixel = image.getPixel((int)x,(int)y);
                k.setText(Integer.toString(pixel)); 

it is showing me an error.......

05-24 13:29:38.101: E/AndroidRuntime(21987): FATAL EXCEPTION: main
05-24 13:29:38.101: E/AndroidRuntime(21987): java.lang.NullPointerException
05-24 13:29:38.101: E/AndroidRuntime(21987):    at com.example.nam.FirstImage.pageinfo(FirstImage.java:100)
05-24 13:29:38.101: E/AndroidRuntime(21987):    at com.example.nam.FirstImage.onTouch(FirstImage.java:63)
05-24 13:29:38.101: E/AndroidRuntime(21987):    at android.view.View.dispatchTouchEvent(View.java:3881)
05-24 13:29:38.101: E/AndroidRuntime(21987):    at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:869)
05-24 13:29:38.101: E/AndroidRuntime(21987):    at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:869)
05-24 13:29:38.101: E/AndroidRuntime(21987):    at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:869)
05-24 13:29:38.101: E/AndroidRuntime(21987):    at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:869)
05-24 13:29:38.101: E/AndroidRuntime(21987):    at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:869)
05-24 13:29:38.101: E/AndroidRuntime(21987):    at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:869)
05-24 13:29:38.101: E/AndroidRuntime(21987):    at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:869)
05-24 13:29:38.101: E/AndroidRuntime(21987):    at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:1769)
05-24 13:29:38.101: E/AndroidRuntime(21987):    at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1135)
05-24 13:29:38.101: E/AndroidRuntime(21987):    at android.app.Activity.dispatchTouchEvent(Activity.java:2096)
05-24 13:29:38.101: E/AndroidRuntime(21987):    at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:1753)
05-24 13:29:38.101: E/AndroidRuntime(21987):    at android.view.ViewRoot.deliverPointerEvent(ViewRoot.java:2227)
05-24 13:29:38.101: E/AndroidRuntime(21987):    at android.view.ViewRoot.handleMessage(ViewRoot.java:1886)
05-24 13:29:38.101: E/AndroidRuntime(21987):    at android.os.Handler.dispatchMessage(Handler.java:99)
05-24 13:29:38.101: E/AndroidRuntime(21987):    at android.os.Looper.loop(Looper.java:130)
05-24 13:29:38.101: E/AndroidRuntime(21987):    at android.app.ActivityThread.main(ActivityThread.java:3687)
05-24 13:29:38.101: E/AndroidRuntime(21987):    at java.lang.reflect.Method.invokeNative(Native Method)
05-24 13:29:38.101: E/AndroidRuntime(21987):    at java.lang.reflect.Method.invoke(Method.java:507)
05-24 13:29:38.101: E/AndroidRuntime(21987):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:867)
05-24 13:29:38.101: E/AndroidRuntime(21987):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:625)
05-24 13:29:38.101: E/AndroidRuntime(21987):    at dalvik.system.NativeStart.main(Native Method)

edit ::::

public class FirstImage extends ImageView implements OnTouchListener {


    MotionEvent event;
    TextView k;
    int rid;
    int pixel;
    Bitmap image;
    String huma ="human";
    String info = "human";
     float x = 0; //init value 
     float y = 0; //init value
     Animation animationFadeIn;
    int t=0;
    int i=1;

    public FirstImage(Context context) { 
        super(context); 
        k=(TextView)findViewById(R.id.textView1);



        } 
    public FirstImage(Context context, AttributeSet attrs) { 
        super(context, attrs);
        k=(TextView)findViewById(R.id.textView1);
        } 


    public void changeImage(int id){

                    this.setImageResource(id);
                rid=id;
                    final Animation animationFadeout=AnimationUtils.loadAnimation(getContext(), R.anim.zoomin);
                    this.startAnimation(animationFadeout);
                    this.setOnTouchListener(this);

    }
    @Override
    public boolean onTouch(View arg0, MotionEvent me) {

        switch(me.getAction()){
        case MotionEvent.ACTION_DOWN:
            x=me.getX();
            y= me.getY();
            pageinfo(x,y);
            break;
        case MotionEvent.ACTION_MOVE:
            x=me.getX();
            y= me.getY();
            pageinfo(x,y);
            break;
        case MotionEvent.ACTION_UP:
            x=me.getX();
            y= me.getY();
            pageinfo(x,y);
            break;
        case MotionEvent.ACTION_OUTSIDE:
            x=me.getX();
            y= me.getY();
            pageinfo(x,y);
            break;
        default: return true;
        }
        return false;
    }
    public void pageinfo(float x, float y) {
        // TODO Auto-generated method stub

         if(rid==R.drawable.cell){
                image  = BitmapFactory.decodeResource(getResources(), rid);
                pixel = image.getPixel((int)x,(int)y);
                k.setText(Integer.toString(pixel));

                }
}

Answer 1

You are getting a NullPointerException because your k member is null;

It is declared and used an ImageView extendsion, and initialized using findViewById which returns back null. Using the same code (findViewById) from within the parent Activity gives back the desired TextView instance.

You should remove the k member from your FirstImage class, and when you get the pixel value at an onTouch event, pass it to the Activity: let it handle the other gui stuff:

So change your FirstImage as:

pixel = image.getPixel((int)x,(int)y);
((AshActivity) getContext()).writePixelIntoK(pixel);

and implement the writePixelIntoK method inside your main activity, e.g.:

public void writePixelIntoK(int pixel)
{
    k.setText("pixel touched: " + pixel);
}