How to get the current displayed image position?

Question

I want to display images front and back. Like Windows Picture and Fax Viewer. This is my code:

package com.my.imagechange; import android.app.Activity; import android.os.Bundle; import android.view.View; import android.widget.Button; import android.widget.ImageButton; import android.widget.ImageView; public class ImageChangeDemo extends Activity { /** Called when the activity is first created. */ // private Gallery gallery; private ImageView imgView; int i=0; int j=6; ImageButton btrt,btlt; Button bt1,bt2; private Integer[] Imgid ={R.drawable.androidlogo,R.drawable.androids, R.drawable.cool, R.drawable.cupcake2009, R.drawable.donut2009, R.drawable.eclair2009}; int imglength=Imgid.length; //System.out.println(imglength); @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.imagechange); System.out.println(imglength); btlt=(ImageButton)findViewById(R.id.bt1); btrt=(ImageButton)findViewById(R.id.bt2); imgView = (ImageView)findViewById(R.id.ImageView01); imgView.setImageResource(Imgid[0]); btlt.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { int choice1=j--; switch(choice1) { case 5:imgView.setImageResource(Imgid[5]); break; case 4:imgView.setImageResource(Imgid[4]); break; case 3:imgView.setImageResource(Imgid[3]); break; case 2:imgView.setImageResource(Imgid[2]); break; case 1:imgView.setImageResource(Imgid[1]); break; } } }); btrt.setOnClickListener(new View.OnClickListener() { @SuppressWarnings("unused") @Override public void onClick(View v) { int choice2=i++; switch(choice2) { case 1:imgView.setImageResource(Imgid[1]); break; case 2:imgView.setImageResource(Imgid[2]); break; case 3:imgView.setImageResource(Imgid[3]); break; case 4:imgView.setImageResource(Imgid[4]); break; case 5:imgView.setImageResource(Imgid[5]); break; } } }); }} 

It works fine, but when I click back it doesn't work. Where did I make my mistake? Can anyone tell me?

Thanks in advance.

Answer 1

Hi, the code is working fine now. My code

 package com.my.imagechange; import android.app.Activity; import android.os.Bundle; import android.view.View; import android.widget.ImageButton; import android.widget.ImageView; public class ImageChange extends Activity { private Gallery gallery; private ImageView imgView; private ImageButton btlt,btrt; private Integer[] Imgid= { R.drawable.androidlogo, R.drawable.androids, R.drawable.cool, R.drawable.cupcake2009, R.drawable.donut2009, R.drawable.eclair2009}; int imglength=Imgid.length; int img_position; int img_minus; int img_plus; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); imgView = (ImageView)findViewById(R.id.ImageView01); imgView.setImageResource(Imgid[0]); btlt=(ImageButton)findViewById(R.id.bt1); btrt=(ImageButton)findViewById(R.id.bt2); System.out.println("----->"+imglength +"----->"); btlt.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { // TODO Auto-generated method stub btrt.setEnabled(true); System.out.println("left button has been clicked"); System.out.println("position: "+img_position); img_minus=--img_position; System.out.println("minus:"+img_minus); imgView.setImageResource(Imgid[img_minus]); //imgView.setBackgroundDrawable(getResources().getDrawable(id)); if(img_minus==0) { btlt.setEnabled(false); } } }); btrt.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { // TODO Auto-generated method stub btlt.setEnabled(true); System.out.println("right button has been clicked"); System.out.println("position: "+img_position); img_plus=++img_position; System.out.println("plus: "+img_plus); imgView.setImageResource(Imgid[img_plus]); if(img_plus==5) { btrt.setEnabled(false); } } }); } } 

main.xml

  <?xml version="1.0" encoding="utf-8"?> <LinearLayout android:id="@+id/LinearLayout01" android:layout_width="fill_parent" android:layout_height="fill_parent" xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:background="#ffffff"> <ImageView android:id="@+id/ImageView01" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_gravity="center" android:background="@drawable/androidlogo"/> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" android:gravity="bottom" android:layout_gravity="fill_horizontal" > <ImageButton android:id="@+id/bt1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:src="@drawable/butleft" android:layout_alignParentLeft="true"> </ImageButton> <ImageButton android:id="@+id/bt2" android:src="@drawable/butright" android:layout_height="wrap_content" android:layout_width="wrap_content" android:layout_alignParentRight="true"> </ImageButton> </RelativeLayout> </LinearLayout> 

Answer 2

Please change this as

 int choice1=--j; 

Edit: The problem here is that after executing this code, int choice1=j--; choice1 contains a value of 6 that is not in the switch enclosure