怎么优化ListView？

         public View getView( int position, View convertView, ViewGroup parent) {

            if (convertView == null) {

                convertView = LayoutInflater.from(ConversationActivity. this).inflate(R.layout.layout_conversation_item,

                        null);

                ConversationItemTag tag = new ConversationItemTag();

                tag. portaitView = (PortraitView) convertView.findViewById(R.id.conv_portrait );

                tag. nameView = (TextView) convertView.findViewById(R.id.conv_name );

                tag. noteView = (TextView) convertView.findViewById(R.id.conv_note );

                tag. dateView = (TextView) convertView.findViewById(R.id.conv_date );

                tag. countView = (TextView) convertView.findViewById(R.id.conv_count );

               

                tag. newmsgView = (TextView) convertView.findViewById(R.id.public_account_new_msg );

               

                convertView.setTag(tag);

            }

            ConversationItemTag tag = (ConversationItemTag) convertView.getTag();

               ...

     }

            

1. 复用convertView 

2. 若一个convertView新生成，将它的子View对象存起来，不用每次在控件树里再找一遍

先看一下复用机制：
http://blog.csdn.net/dxswzj/article/details/10701783
例子：


在回收池里（mScrapViews）木有view的时候，输入参数convertView是null，否则，输入参数是回收池里的某view。


然后复用之。


public View getView (int position, View convertView, ViewGroup parent) {


                     View v;
                      if (convertView != null)
                           v = convertView;
                      else {
                           LayoutInflater li = getLayoutInflater();
                           v = li.inflate(R.layout.agenda_conf_hall_item ,
                                          null);
                     }
。。。
}




@param position The position of the item within the adapter's data set of the item whose view
     *        we want.
     * @param convertView The old view to reuse, if possible. Note: You should check that this view
     *        is non-null and of an appropriate type before using. If it is not possible to convert
     *        this view to display the correct data, this method can create a new view.
     *        Heterogeneous lists can specify their number of view types, so that this View is
     *        always of the right type (see {@link #getViewTypeCount()} and
     *        {@link #getItemViewType(int)}).
     * @param parent The parent that this view will eventually be attached to
@return A View corresponding to the data at the specified position.
View getView(int position, View convertView, ViewGroup parent);


     private View[] mActiveViews = new View[0];
     private ArrayList<View>[] mScrapViews;


        void fillActiveViews(int childCount, int firstActivePosition) {
            if (mActiveViews.length < childCount) {
                mActiveViews = new View[childCount];
            }
            mFirstActivePosition = firstActivePosition;


            final View[] activeViews = mActiveViews;
            for (int i = 0; i < childCount; i++) {
                View child = getChildAt(i);
                AbsListView.LayoutParams lp = (AbsListView.LayoutParams) child.getLayoutParams();
                // Don't put header or footer views into the scrap heap
                if (lp != null && lp.viewType != ITEM_VIEW_TYPE_HEADER_OR_FOOTER) {
                    // Note:  We do place AdapterView.ITEM_VIEW_TYPE_IGNORE in active views.
                    //        However, we will NOT place them into scrap views.
                    activeViews[i] = child;
                }
            }
        }


//回收机制：


View obtainView(int position, boolean[] isScrap) {
        isScrap[0] = false;
        View scrapView;


        scrapView = mRecycler.getTransientStateView(position);
        if (scrapView != null) {
            return scrapView;
        }
        //在mScrapViews拿对应位置的view
        scrapView = mRecycler.getScrapView(position);


        View child;
          //若能拿到
        if (scrapView != null) {
            child = mAdapter.getView(position, scrapView, this);


            if (child.getImportantForAccessibility() == IMPORTANT_FOR_ACCESSIBILITY_AUTO) {
                child.setImportantForAccessibility(IMPORTANT_FOR_ACCESSIBILITY_YES);
            }
              //若新建了一个子View
            if (child != scrapView) {
               //把老View放到mScrapViews里面，返回新View
                mRecycler.addScrapView(scrapView, position);
                if (mCacheColorHint != 0) {
                    child.setDrawingCacheBackgroundColor(mCacheColorHint);
                }
          //若没有新建子View
            } else {
                isScrap[0] = true;
                child.dispatchFinishTemporaryDetach();
            }
          //若不能拿到，新建一个子View
        } else {
            child = mAdapter.getView(position, null, this);


            if (child.getImportantForAccessibility() == IMPORTANT_FOR_ACCESSIBILITY_AUTO) {
                child.setImportantForAccessibility(IMPORTANT_FOR_ACCESSIBILITY_YES);
            }


            if (mCacheColorHint != 0) {
                child.setDrawingCacheBackgroundColor(mCacheColorHint);
            }
        }


        if (mAdapterHasStableIds) {
            final ViewGroup.LayoutParams vlp = child.getLayoutParams();
            LayoutParams lp;
            if (vlp == null) {
                lp = (LayoutParams) generateDefaultLayoutParams();
            } else if (!checkLayoutParams(vlp)) {
                lp = (LayoutParams) generateLayoutParams(vlp);
            } else {
                lp = (LayoutParams) vlp;
            }
            lp.itemId = mAdapter.getItemId(position);
            child.setLayoutParams(lp);
        }


        if (AccessibilityManager.getInstance(mContext).isEnabled()) {
            if (mAccessibilityDelegate == null) {
                mAccessibilityDelegate = new ListItemAccessibilityDelegate();
            }
            if (child.getAccessibilityDelegate() == null) {
                child.setAccessibilityDelegate(mAccessibilityDelegate);
            }
        }


        return child;
    }