public ListView(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {super(context, attrs, defStyleAttr, defStyleRes);//TypedArray实例是个属性的容器，context.obtainStyledAttributes()方法返回得到final TypedArray a = context.obtainStyledAttributes(attrs, com.android.internal.R.styleable.ListView, defStyleAttr, defStyleRes);//从属性处初始化值 CharSequence[] entries = a.getTextArray(com.android.internal.R.styleable.ListView_entries);//如果值不为null,shezhi moren de buju fangshiif (entries != null) {setAdapter(new ArrayAdapter<CharSequence>(context,com.android.internal.R.layout.simple_list_item_1, entries));} //系统自带的风格线final Drawable d = a.getDrawable(com.android.internal.R.styleable.ListView_divider);if (d != null) {// If a divider is specified use its intrinsic height for divider heightsetDivider(d);} //设置listview头部final Drawable osHeader = a.getDrawable(com.android.internal.R.styleable.ListView_overScrollHeader);if (osHeader != null) {setOverscrollHeader(osHeader);} //设置listview底部final Drawable osFooter = a.getDrawable(com.android.internal.R.styleable.ListView_overScrollFooter);if (osFooter != null) {setOverscrollFooter(osFooter);}//设置listview Item的间距final int dividerHeight = a.getDimensionPixelSize(com.android.internal.R.styleable.ListView_dividerHeight, 0);if (dividerHeight != 0) {setDividerHeight(dividerHeight);}mHeaderDividersEnabled = a.getBoolean(R.styleable.ListView_headerDividersEnabled, true);mFooterDividersEnabled = a.getBoolean(R.styleable.ListView_footerDividersEnabled, true);a.recycle();}public int getMaxScrollAmount() {return (int) (MAX_SCROLL_FACTOR * (mBottom - mTop));} private void adjustViewsUpOrDown() { final int childCount = getChildCount(); int delta; if (childCount > 0) { View child; if (!mStackFromBottom) { // Uh-oh -- we came up short. Slide all views up to make them // align with the top child = getChildAt(0); delta = child.getTop() - mListPadding.top; if (mFirstPosition != 0) { // It‘s OK to have some space above the first item if it is // part of the vertical spacing delta -= mDividerHeight; } if (delta < 0) { // We only are looking to see if we are too low, not too high delta = 0; } } else { // we are too high, slide all views down to align with bottom child = getChildAt(childCount - 1); delta = child.getBottom() - (getHeight() - mListPadding.bottom); if (mFirstPosition + childCount < mItemCount) { // It‘s OK to have some space below the last item if it is // part of the vertical spacing delta += mDividerHeight; } if (delta > 0) { delta = 0; } } if (delta != 0) { offsetChildrenTopAndBottom(-delta); } } }接下来是添加头部的方法；为ListView顶部添加一个固定的View，如果HeaderView多于一个，会按照添加的顺序进行排列：public void addHeaderView(View v, Object data, boolean isSelectable) { final FixedViewInfo info = new FixedViewInfo(); info.view = v; info.data = data; info.isSelectable = isSelectable; mHeaderViewInfos.add(info); mAreAllItemsSelectable &= isSelectable; // Wrap the adapter if it wasn‘t already wrapped. if (mAdapter != null) { if (!(mAdapter instanceof HeaderViewListAdapter)) { mAdapter = new HeaderViewListAdapter(mHeaderViewInfos, mFooterViewInfos, mAdapter); } // In the case of re-adding a header view, or adding one later on, // we need to notify the observer. if (mDataSetObserver != null) { mDataSetObserver.onChanged(); } } }public void addHeaderView(View v) {addHeaderView(v, null, true);}@Overridepublic int getHeaderViewsCount() {return mHeaderViewInfos.size();}public boolean removeHeaderView(View v) {//如果头部信息的list>0,并且Adapter不为null，删除头部信息，并进行回调if (mHeaderViewInfos.size() > 0) {boolean result = false;if (mAdapter != null && ((HeaderViewListAdapter) mAdapter).removeHeader(v)) {if (mDataSetObserver != null) {mDataSetObserver.onChanged();}result = true;}removeFixedViewInfo(v, mHeaderViewInfos);return result;}return false;}private void removeFixedViewInfo(View v, ArrayList<FixedViewInfo> where) { int len = where.size(); for (int i = 0; i < len; ++i) { FixedViewInfo info = where.get(i); if (info.view == v) { where.remove(i); break; } } }/** * Add a fixed view to appear at the bottom of the list. If addFooterView is * called more than once, the views will appear in the order they were * added. Views added using this call can take focus if they want. * <p> * NOTE: Call this before calling setAdapter. This is so ListView can wrap * the supplied cursor with one that will also account for header and footer * views. * * @param v The view to add. * @param data Data to associate with this view * @param isSelectable true if the footer view can be selected */ public void addFooterView(View v, Object data, boolean isSelectable) { // NOTE: do not enforce the adapter being null here, since unlike in // addHeaderView, it was never enforced here, and so existing apps are // relying on being able to add a footer and then calling setAdapter to // force creation of the HeaderViewListAdapter wrapper FixedViewInfo info = new FixedViewInfo(); info.view = v; info.data = data; info.isSelectable = isSelectable; mFooterViewInfos.add(info); // in the case of re-adding a footer view, or adding one later on, // we need to notify the observer if (mAdapter != null && mDataSetObserver != null) { mDataSetObserver.onChanged(); } } /** * Add a fixed view to appear at the bottom of the list. If addFooterView is called more * than once, the views will appear in the order they were added. Views added using * this call can take focus if they want. * <p>NOTE: Call this before calling setAdapter. This is so ListView can wrap the supplied * cursor with one that will also account for header and footer views. * * * @param v The view to add. */ public void addFooterView(View v) { addFooterView(v, null, true); }@Override public int getFooterViewsCount() { return mFooterViewInfos.size(); }/** * Removes a previously-added footer view. * * @param v The view to remove * @return * true if the view was removed, false if the view was not a footer view */ public boolean removeFooterView(View v) { if (mFooterViewInfos.size() > 0) { boolean result = false; if (mAdapter != null && ((HeaderViewListAdapter) mAdapter).removeFooter(v)) { if (mDataSetObserver != null) { mDataSetObserver.onChanged(); } result = true; } removeFixedViewInfo(v, mFooterViewInfos); return result; } return false; } /** * Returns the adapter currently in use in this ListView. The returned adapter * might not be the same adapter passed to {@link #setAdapter(ListAdapter)} but * might be a {@link WrapperListAdapter}. *返回listview当前正在使用的Adapter，adapter不一定是通过setAdapter方法传入的adapter，有可能是一个WrapperListAdapter * @return The adapter currently used to display data in this ListView. * * @see #setAdapter(ListAdapter) */ @Override public ListAdapter getAdapter() { return mAdapter; }/** * Sets the data behind this ListView. * * The adapter passed to this method may be wrapped by a {@link WrapperListAdapter}, * depending on the ListView features currently in use. For instance, adding * headers and/or footers will cause the adapter to be wrapped. * 通过setAdapter方法添加的adapter根据当前ListView的使用情况可能被装饰为一个WrapperListAdapter，比如说添加一个HeaderView或者FooterView。
在该方法中，先把以前的数据和观察者去掉，然后再重新设置各种参数
* @param adapter The ListAdapter which is responsible for maintaining the * data backing this list and for producing a view to represent an * item in that data set. * * @see #getAdapter() */ @Override public void setAdapter(ListAdapter adapter) { if (mAdapter != null && mDataSetObserver != null) { mAdapter.unregisterDataSetObserver(mDataSetObserver); } resetList(); mRecycler.clear(); if (mHeaderViewInfos.size() > 0|| mFooterViewInfos.size() > 0) { mAdapter = new HeaderViewListAdapter(mHeaderViewInfos, mFooterViewInfos, adapter); } else { mAdapter = adapter; } mOldSelectedPosition = INVALID_POSITION; mOldSelectedRowId = INVALID_ROW_ID; // AbsListView#setAdapter will update choice mode states. super.setAdapter(adapter); if (mAdapter != null) { mAreAllItemsSelectable = mAdapter.areAllItemsEnabled(); mOldItemCount = mItemCount; mItemCount = mAdapter.getCount(); checkFocus(); mDataSetObserver = new AdapterDataSetObserver(); mAdapter.registerDataSetObserver(mDataSetObserver); mRecycler.setViewTypeCount(mAdapter.getViewTypeCount()); int position; if (mStackFromBottom) { position = lookForSelectablePosition(mItemCount - 1, false); } else { position = lookForSelectablePosition(0, true); } setSelectedPositionInt(position); setNextSelectedPositionInt(position); if (mItemCount == 0) { // Nothing selected checkSelectionChanged(); } } else { mAreAllItemsSelectable = true; checkFocus(); // Nothing selected checkSelectionChanged(); } requestLayout(); }/** * The list is empty. Clear everything out. * */ @Override void resetList() { // The parent‘s resetList() will remove all views from the layout so we need to // cleanup the state of our footers and headers clearRecycledState(mHeaderViewInfos); clearRecycledState(mFooterViewInfos); super.resetList(); mLayoutMode = LAYOUT_NORMAL; }private void clearRecycledState(ArrayList<FixedViewInfo> infos) { if (infos != null) { final int count = infos.size(); for (int i = 0; i < count; i++) { final View child = infos.get(i).view; final LayoutParams p = (LayoutParams) child.getLayoutParams(); if (p != null) { p.recycledHeaderFooter = false; } } } }
原文：http://www.cnblogs.com/androidsuperman/p/4243025.html