Question

In my projects I kept different images for categories. When I click on each category image I am passing its category id to other page statically and setting the drawable image of that category in the new page.

My Code:

Firstpage.java

public static String categoryid;

category1.setOnClickListener(new View.OnClickListener()
{
   public void onClick(View view)
    {
     categoryid="0";
     Intent myIntent = new Intent(view.getContext(),Nextpage.class);
     startActivityForResult(myIntent, 0);
    }
});
category2.setOnClickListener(new View.OnClickListener()
{
   public void onClick(View view)
   {
    categoryid="1";
    Intent myIntent = new Intent(view.getContext(),Nextpage.class);
    startActivityForResult(myIntent, 0);
   }
});
category3.setOnClickListener(new View.OnClickListener()
{
   public void onClick(View view)
   {
    categoryid="2";
    Intent myIntent = new Intent(view.getContext(),Nextpage.class);
    startActivityForResult(myIntent, 0);
   }
});

Nextpage.java

public static String catid = Firstpage.categoryid;
          ImageView categorytype=(ImageView)findViewById(R.id.imageView1);

             if(catid=="0")
            { 
                categorytype.setBackgroundResource(R.drawable.image1);
            }

             else if(catid=="1")
            { 
                categorytype.setBackgroundResource(R.drawable.image2);
            }
           else  if(catid=="2")
            {
                   categorytype.setBackgroundResource(R.drawable.image3);
            }

First time when I am clicking on the category image it is passing the category id to the next page and that particular image is setting in the nextpage. After that I clicked the back button(android back button) and went to Firstpage.java and again clicked on other image. But this time also the same image stored. The category id didnt changed. The category id is not refreshing…How to refresh the category id? Any suggestion will be thankful…..

Answer 1

Don’t use static variables for this. Pass the category ID to your Nextpage activity through the intent. In Firstpage.java:

public static final String CATEGORY_KEY = "category";

category1.setOnClickListener(new View.OnClickListener()
{
   public void onClick(View view)
    {
     Intent myIntent = new Intent(this,Nextpage.class);
     myIntent.putExtra(CATEGORY_KEY, "0");
     startActivityForResult(myIntent, 0);
    }
});

Then retrieve it in the onCreate(Bundle) method of Nextpage.java:

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    Intent intent = getIntent();
    String categoryid = intent.getStringExtra(Firstpage.CATEGORY_KEY);
    . . .
}

The reason your method doesn’t work is that Nextpage.catid is initialized when the class is loaded, but the assignment statement is not executed again unless the class is unloaded and needs to be reloaded.