Question

I have a program which uses view flipper I am getting a NullPointerException as follows when the activity is called. I wish to cycle through a set of images as long as the activity is being run.

06-13 18:52:05.358: E/AndroidRuntime(368): Caused by: java.lang.NullPointerException

Activity:

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.view.View;
import android.view.ViewGroup.LayoutParams;
import android.view.animation.AnimationUtils;
import android.widget.ImageView;
import android.widget.ViewFlipper;


public class MainMenuActivity extends Activity{

     Handler handler;
     Runnable runnable;
     ViewFlipper imageSwitcher;
    @Override
        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.menupage);

            imageSwitcher= (ViewFlipper) new ViewFlipper(this).findViewById(R.id.sportspersons);
            this.viewchanger();

        }

    public void viewchanger()
    {
        imageSwitcher.setInAnimation(this, R.anim.fadein);  
        imageSwitcher.setOutAnimation(this, R.anim.fadeout); 

        ImageView i = new ImageView(this);
        i.setBackgroundDrawable(getResources().getDrawable(R.drawable.jowens));
        ImageView i2 = new ImageView(this);
        i2.setBackgroundDrawable(getResources ().getDrawable(R.drawable.maradonna));
        ImageView i3 = new ImageView(this);
        i2.setBackgroundDrawable(getResources().getDrawable(R.drawable.mjordan));
        ImageView i4 = new ImageView(this);
        i2.setBackgroundDrawable(getResources().getDrawable(R.drawable.pele));
        imageSwitcher.addView(i);
        imageSwitcher.addView(i2);
        imageSwitcher.addView(i3);
        imageSwitcher.addView(i4);

        runnable = new Runnable() {

            @Override
            public void run() {
                handler.postDelayed(runnable, 3000);
                imageSwitcher.showNext();

            }
        };
        handler.postDelayed(runnable, 500);
    }
}

XML:

<?xml version="1.0" encoding="utf-8"?>
<AbsoluteLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >
      <ImageView
        android:id="@+id/imageView2"
        android:layout_width="match_parent"
        android:layout_height="508dp"
        android:layout_x="-4dp"
        android:layout_y="-5dp"
        android:scaleType="fitXY"
        android:src="@drawable/mainmenu01" />

        <ViewFlipper 
           android:id="@+id/sportspersons"  
           android:layout_width="86dp"
           android:layout_height="91dp"
           android:layout_x="38dp"
        android:layout_y="373dp" />  
</AbsoluteLayout>

Answer 1

You can try this way:

runnable = new Runnable() {

        @Override
        public void run() {
            handler.postDelayed(runnable, 3000);
            imageSwitcher.setAutoStart(true);  
            imageSwitcher.startFlipping();
        }
    };