Android dynamic gridview

问题

i want to create infinie GridView, and when i scroll, if in onScroll method not add

adapter = new ImageAdapter();
            grid.setAdapter(adapter);

my app crashes with LogCat:

FATAL EXCEPTION: main
java.lang.IndexOutOfBoundsException: Invalid index 46, size is 46
    at java.util.ArrayList.throwIndexOutOfBoundsException(ArrayList.java:251)
    at java.util.ArrayList.get(ArrayList.java:304)
    at com.example.tectob6iu.MainActivity$ImageAdapter.getView(MainActivity.java:98)
    at android.widget.AbsListView.obtainView(AbsListView.java:2143)
    at android.widget.GridView.makeAndAddView(GridView.java:1341)
    at android.widget.GridView.makeRow(GridView.java:341)
    at android.widget.GridView.fillDown(GridView.java:283)
    at android.widget.GridView.fillGap(GridView.java:243)
    at android.widget.AbsListView.trackMotionScroll(AbsListView.java:4930)
    at android.widget.AbsListView$FlingRunnable.run(AbsListView.java:4087)
    at android.view.Choreographer$CallbackRecord.run(Choreographer.java:749)
    at android.view.Choreographer.doCallbacks(Choreographer.java:562)
    at android.view.Choreographer.doFrame(Choreographer.java:531)
    at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:735)
    at android.os.Handler.handleCallback(Handler.java:725)
    at android.os.Handler.dispatchMessage(Handler.java:92)
    at android.os.Looper.loop(Looper.java:137)
    at android.app.ActivityThread.main(ActivityThread.java:5191)
    at java.lang.reflect.Method.invokeNative(Native Method)
    at java.lang.reflect.Method.invoke(Method.java:511)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:795)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:562)
    at dalvik.system.NativeStart.main(Native Method)

MainActivity.class

public class MainActivity extends Activity  implements OnScrollListener{
    private  class ImageAdapter extends BaseAdapter {
        private List<String> list;
        private ImageLoader loader;
        private DisplayImageOptions options;


        public ImageAdapter() {
            this(new ArrayList<String>());

           options = new DisplayImageOptions.Builder()
            .cacheInMemory()
            .cacheOnDisc()
            .bitmapConfig(Bitmap.Config.RGB_565)
            .displayer(new FadeInBitmapDisplayer(250))
            .build();

           loader = ImageLoader.getInstance();
           loader.init(ImageLoaderConfiguration.createDefault(MainActivity.this));
        }

        public void clear() {
            list.clear();
            notifyDataSetChanged();
        }

        public void add(List<String> rows) {
            list.addAll(rows);
            notifyDataSetChanged();
        }



        @Override
        public int getCount() {
            return list.size();
        }

        @Override
        public long getItemId(int position) {
            return position;
        }

        @Override
        public String getItem(int position) {
            return list.get(position);
        }

        public View getView(int position, View view, ViewGroup container) {
            if (view == null) {
                view = getLayoutInflater().inflate(R.layout.grid_item, container, false);
            }

            ImageView image = (ImageView)view.findViewById(R.id.imageGrid);
            // Bind row on your view here      97
            //98
            if(str.size() > 0){
                    loader.displayImage(str.get(position), image, options);
            }
            else{
                image.setImageResource(R.drawable.ic_launcher);
            }
            return view;
        }

        public ImageAdapter(List<String> list) {
            this.list = list;
        }
    }

     class LoadTask extends AsyncTask<Void, Void, List<String>> {

        private int page = 1;

        public int addPage(int i){
            return page = i;
        }

        @Override
        protected List<String> doInBackground(Void... params) {

            InputStream ips = null; 
            JSONObject jsonObj = null;
            String json = "";       
            try {
                DefaultHttpClient httpClient = new DefaultHttpClient();
                HttpResponse response = httpClient.execute(new HttpPost("http://iapp.gazeta.uz/fotolenta?page="+page)); 
                ips = response.getEntity().getContent();
            } catch (ClientProtocolException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }

            try {
                BufferedReader bufff = new BufferedReader(new InputStreamReader(ips, "UTF-8"));
                StringBuilder sb = new StringBuilder();
                String line = null;

                while ((line = bufff.readLine()) != null){
                    sb.append(line + "\n");                 
                }
                ips.close();
                json = sb.toString();       
            } catch (Exception e) {
                e.printStackTrace();
            }

            try {
                jsonObj = new JSONObject(json);
            } catch (JSONException e) {
                e.printStackTrace();
            }

            JSONArray array = null;
            array = jsonObj.optJSONArray("img_list");


                for (int i = 0; i < array.length(); i++) {
                    str.add(array.optJSONObject(i).optString("thumbnail"));             
                }
            return str;
        }

        @Override
        protected void onPostExecute(List<String> result) {
            adapter.add(result);
        }
    }

    ArrayList<String> str = new ArrayList<String>();

    private GridView grid;
    private ImageAdapter adapter;
    private int page;

    private int mVisibleThreshold = 5;
    private int mCurrentPage = 0;
    private int mPreviousTotal = 0;
    private boolean mLoading = true;
    private boolean mLastPage = false;

    public void refresh(int i){
        LoadTask task = new LoadTask();
        task.addPage(i);
        task.execute();
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        page = 1;
        refresh(page);       

        setContentView(R.layout.main);
        grid = (GridView) findViewById(R.id.grid);

        adapter = new ImageAdapter();
        grid.setAdapter(adapter);

        grid.setOnScrollListener(this);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu){

        getMenuInflater().inflate(R.menu.activity_main, menu);

        return super.onCreateOptionsMenu(menu);
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item){

        page ++;
        refresh(page);
        adapter = new ImageAdapter();
        grid.setAdapter(adapter);

        return super.onOptionsItemSelected(item);
    }



    @Override
    public void onScroll(AbsListView view, int firstVisibleItem,
            int visibleItemCount, int totalItemCount) {
        // TODO Auto-generated method stub
        if (mLoading) {
            if (totalItemCount > mPreviousTotal) {

                mLoading = false;
                mPreviousTotal = totalItemCount;
                mCurrentPage++;

                // Find your own condition in order to know when you 
                // have finished displaying all items
                if (mCurrentPage + 1 > 50) {
                    mLastPage = true;
                }
            }
        }
        if (!mLastPage && !mLoading && 
                (totalItemCount - visibleItemCount) <= (firstVisibleItem + mVisibleThreshold)) {
            page++;
            refresh(page);
            adapter = new ImageAdapter();
            grid.setAdapter(adapter);

            mLoading = true;
        }
    }

    @Override
    public void onScrollStateChanged(AbsListView view, int scrollState) {
        // TODO Auto-generated method stub

    }

}

else my app work but when i scroll to end grid view refresh and lost position and i need again scroll to my last position, how fix this problem?

回答1:

Try to check this condition :

if(str.size() > 0 && position < str.size()){
      loader.displayImage(str.get(position), image, options);
}

Instead of

if(str.size() > 0){
      loader.displayImage(str.get(position), image, options);
}

Hope it helps you.

Thanks.

来源：https://stackoverflow.com/questions/13945941/android-dynamic-gridview