Get Errs when Using Thread In Android

Question

I create a simple Project to load all images in drawable

Here is my code

public void onCreate(Bundle savedInstanceState) 
{
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    list = (ImageView)findViewById(R.id.tung);
    ct = getApplicationContext();
    try
    {
        IDs = getAllResourceIDs(R.drawable.class);
        n= IDs.length;
        dem=0;
        list.setOnClickListener(new View.OnClickListener()
         {
            public void onClick(View v)
            {
                ++dem;
                list.setImageResource(IDs[dem]);
                if(dem==n-1)
                    dem=0;
            }
        });

        Thread x = new Thread(
                new Runnable ()
                {
                    public void run()
                    {
                        while(true)
                        {
                            try
                            {
                                ++dem;
                                //Toast.makeText(ct, ""+dem, 20).show();
                                list.setImageResource(IDs[dem]);
                                if(dem==n-1)
                                    dem=0;
                            }
                            catch(Exception e)
                            {
                                //Toast.makeText(ct,e.toString(), 200).show();
                            }
                        }
                    }
                }
                );
        x.start();
    }
    catch(Exception e)
    {
        Toast.makeText(this,e.toString(), 200).show();
    }
}

anh here is getAllResourceIDs function to get all ids

private int[] getAllResourceIDs(Class<?> aClass) throws IllegalArgumentException{
    /* Get all Fields from the class passed. */
    Field[] IDFields = aClass.getFields();

    /* int-Array capable of storing all ids. */
    int[] IDs = new int[IDFields.length];

    try {
            /* Loop through all Fields and store id to array. */
            for(int i = 0; i < IDFields.length; i++){
                    /* All fields within the subclasses of R
                     * are Integers, so we need no type-check here. */

                    // pass 'null' because class is static
                    IDs[i] = IDFields[i].getInt(null);
            }
    } catch (Exception e) {
            /* Exception will only occur on bad class submitted. */
            throw new IllegalArgumentException();
    }
    return IDs;

the file main.xml has only a ImageView with id = "tung" I tried to load all images using a Thead named x by using code list.setImageResource(IDs[dem]); as you can see in my code but notthing is happen Can you explain it for me ! Thank a lot !

Answer 1

JRaymond ! Thankyou a lot I create a Xthead class extends Thread like this

class XThread extends Thread
{
    public int ids[];
    public ImageView icon;
    public int dem,n;
    XThread(int[] ids ,ImageView icon)
    {
        this.ids = ids;
        this.icon= icon;
        dem=0;
        n = ids.length;
    }

    public void run()
    {
        while(true)
        {
            try
            {
                Thread.sleep(500);
            handle.post(new Runnable()
            {
                public void run()
                {
                    ++dem;
                    icon.setImageResource(ids[dem]);
                    if(dem==n-1)
                        dem=0;
                }
            });
            }
            catch(Exception e)
            {

            }
        }
    }
}

and in onCreate() function

XThread x = new XThread(IDs,list);
        x.start();

Answer 2

Well for starters catch (Exception e) is almost never a good idea, as it hides all of the meaningful information you can get when an error occurs.

Your error in particular is on this line in your background thread:

list.setImageResource(IDs[dem]);

Background threads are not allowed to manipulate UI objects. Instead you need to use either an AsyncTask (simpler) or a Handler (Advanced)