动手分析安卓仿QQ联系人列表TreeView控件
因项目需要需要用到仿QQ联系人列表的控件样式，于是网上找到一个轮子（https://github.com/TealerProg/TreeView），工作完成现在简单分析一下这个源码。
一、 需要用到的知识如下：
①安卓事件分发机制：(http://blog.csdn.net/lvxiangan/article/details/9309927 或 http://gundumw100.iteye.com/blog/1052270）
二、下面简单分析下
项目结构如下
1、ITreeViewHeaderUpdater接口
1 package com.markmao.treeview.widget; 2 3 import android.view.View; 4 5 /** 6 * Update interface TreeView's header . 7 * 8 * @author markmjw 9 * @date 2014-01-04 10 */ 11 public interface ITreeViewHeaderUpdater { 12 /** Header Gone. */ 13 public static final int STATE_GONE = 0x00; 14 /** Header Visible. */ 15 public static final int STATE_VISIBLE_ALL = 0x01; 16 /** Header Push up. */ 17 public static final int STATE_VISIBLE_PART = 0x02; 18 19 /** 20 * Get TreeView's header state. 21 * 22 * @param groupPosition The group position. 23 * @param childPosition The child position. 24 * @return {@link #STATE_GONE}, {@link #STATE_VISIBLE_ALL}, 25 * {@link #STATE_VISIBLE_PART} 26 */ 27 public int getHeaderState(int groupPosition, int childPosition); 28 29 /** 30 * Update TreeView's header. 31 * 32 * @param header The TreeView's header view. 33 * @param groupPosition The group position. 34 * @param childPosition The child position. 35 * @param alpha The header's alpha value. 36 */ 37 public void updateHeader(View header, int groupPosition, int childPosition, int alpha); 38 39 /** 40 * The header view onClick. 41 * 42 * @param groupPosition The group position. 43 * @param status {@link #STATE_GONE}, {@link #STATE_VISIBLE_ALL}, 44 * {@link #STATE_VISIBLE_PART} 45 */ 46 public void onHeaderClick(int groupPosition, int status); 47 48 /** 49 * Get the header's state on click. 50 * 51 * @param groupPosition The group position. 52 * @return {@link #STATE_GONE}, {@link #STATE_VISIBLE_ALL}, 53 * {@link #STATE_VISIBLE_PART} 54 */ 55 public int getHeaderClickStatus(int groupPosition); 56 }
主要定义了三个状态：STATE_GONE：HeaderView处于隐藏不显示状态，STATE_VISIBLE：HeaderView处于显示状态，STATE_VISIBLE_PART：HeaderView处于显示且需要向上推起的临界状态。
2、BaseTreeViewAdapter实现ITreeViewHeaderUpdater接口
package com.markmao.treeview.widget; import android.util.Log; import android.util.SparseIntArray; import android.widget.BaseExpandableListAdapter; /** * The base adapter for TreeView. * * @author markmjw * @date 2014-01-04 */ public abstract class BaseTreeViewAdapter extends BaseExpandableListAdapter implements ITreeViewHeaderUpdater { protected TreeView mTreeView; protected SparseIntArray mGroupStatusArray; public BaseTreeViewAdapter(TreeView treeView) { mTreeView = treeView; mGroupStatusArray = new SparseIntArray(); } @Override public int getHeaderState(int groupPosition, int childPosition) { final int childCount = getChildrenCount(groupPosition); if (childPosition == childCount - 1) { return STATE_VISIBLE_PART; } else if (childPosition == -1 && !mTreeView.isGroupExpanded(groupPosition)) { return STATE_GONE; } else { return STATE_VISIBLE_ALL; } } @Override public void onHeaderClick(int groupPosition, int status) { mGroupStatusArray.put(groupPosition, status); } @Override public int getHeaderClickStatus(int groupPosition) { return mGroupStatusArray.get(groupPosition, STATE_GONE); } }
主要方法：getHeaderState方法，当childPosition==childCount-1条件的时候（及 HeaderView处于显示且需要向上推起的临界状态）时返回STATE_VISIBLE_PART
3、TreeView
package com.markmao.treeview.widget; import android.content.Context; import android.graphics.Canvas; import android.util.AttributeSet; import android.util.Log; import android.view.MotionEvent; import android.view.View; import android.view.ViewGroup; import android.widget.AbsListView; import android.widget.AbsListView.OnScrollListener; import android.widget.ExpandableListAdapter; import android.widget.ExpandableListView; import android.widget.ExpandableListView.OnGroupClickListener; /** * This widget extends {@link android.widget.ExpandableListView}, just like TreeView(IOS). * * @see android.widget.ExpandableListView * @author markmjw * @date 2014-01-03 */ public class TreeView extends ExpandableListView implements OnScrollListener, OnGroupClickListener { private static final int MAX_ALPHA = 255; private ITreeViewHeaderUpdater mUpdater; private View mHeaderView; private boolean mHeaderVisible; private int mHeaderWidth; private int mHeaderHeight; public TreeView(Context context) { super(context); init(); } public TreeView(Context context, AttributeSet attrs) { super(context, attrs); init(); } public TreeView(Context context, AttributeSet attrs, int defStyle) { super(context, attrs, defStyle); init(); } private void init() { setSmoothScrollbarEnabled(true); setOnScrollListener(this); setOnGroupClickListener(this); } /** * Sets the list header view * * @param view */ public void setHeaderView(View view) { mHeaderView = view; AbsListView.LayoutParams lp = new AbsListView.LayoutParams(ViewGroup.LayoutParams .MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT); view.setLayoutParams(lp); if (mHeaderView != null) { setFadingEdgeLength(0); } requestLayout(); } @Override public void setAdapter(ExpandableListAdapter adapter) { super.setAdapter(adapter); if(adapter instanceof ITreeViewHeaderUpdater) { mUpdater = (ITreeViewHeaderUpdater) adapter; } else { throw new IllegalArgumentException("The adapter must instanceof ITreeViewHeaderUpdater."); } } @Override public boolean onTouchEvent(MotionEvent ev) { // header view is visible if (mHeaderVisible) { float downX = 0; float downY = 0; switch (ev.getAction()) { case MotionEvent.ACTION_DOWN: downX = ev.getX(); downY = ev.getY(); if (downX <= mHeaderWidth && downY <= mHeaderHeight) { return true; } break; case MotionEvent.ACTION_UP: float x = ev.getX(); float y = ev.getY(); float offsetX = Math.abs(x - downX); float offsetY = Math.abs(y - downY); // the touch event under header view if (x <= mHeaderWidth && y <= mHeaderHeight && offsetX <= mHeaderWidth && offsetY <= mHeaderHeight) { if (mHeaderView != null) { onHeaderViewClick(); } return true; } break; default: break; } } return super.onTouchEvent(ev); } @Override public boolean onGroupClick(ExpandableListView parent, View v, int groupPosition, long id) { int status = mUpdater.getHeaderClickStatus(groupPosition); switch (status) { case ITreeViewHeaderUpdater.STATE_GONE: mUpdater.onHeaderClick(groupPosition, ITreeViewHeaderUpdater.STATE_VISIBLE_ALL); break; case ITreeViewHeaderUpdater.STATE_VISIBLE_ALL: mUpdater.onHeaderClick(groupPosition, ITreeViewHeaderUpdater.STATE_GONE); break; case ITreeViewHeaderUpdater.STATE_VISIBLE_PART: // ignore break; default: break; } return false; } @Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { super.onMeasure(widthMeasureSpec, heightMeasureSpec); if (mHeaderView != null) { measureChild(mHeaderView, widthMeasureSpec, heightMeasureSpec); mHeaderWidth = mHeaderView.getMeasuredWidth(); mHeaderHeight = mHeaderView.getMeasuredHeight(); } } private int mOldState = -1; @Override protected void onLayout(boolean changed, int left, int top, int right, int bottom) { super.onLayout(changed, left, top, right, bottom); final long listPosition = getExpandableListPosition(getFirstVisiblePosition()); final int groupPos = ExpandableListView.getPackedPositionGroup(listPosition); final int childPos = ExpandableListView.getPackedPositionChild(listPosition); Log.v("TreeView--onlayout分析：",String.format("返回所选择的List %d,返回所选择的组项 %d,返回所选择的子项 %d",(int)listPosition,groupPos,childPos)); int state = mUpdater.getHeaderState(groupPos, childPos); if (mHeaderView != null && mUpdater != null && state != mOldState) { mOldState = state; mHeaderView.layout(0, 0, mHeaderWidth, mHeaderHeight); } updateHeaderView(groupPos, childPos); } @Override protected void dispatchDraw(Canvas canvas) { super.dispatchDraw(canvas); if (mHeaderVisible) { // draw header view drawChild(canvas, mHeaderView, getDrawingTime()); Log.v("TreeView--dispatchDraw分析：","重新绘制mHeaderView"); } } @Override public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) { final long listPosition = getExpandableListPosition(firstVisibleItem); int groupPos = ExpandableListView.getPackedPositionGroup(listPosition); int childPos = ExpandableListView.getPackedPositionChild(listPosition); updateHeaderView(groupPos, childPos); } @Override public void onScrollStateChanged(AbsListView view, int scrollState) { } private void updateHeaderView(int groupPosition, int childPosition) { if (mHeaderView == null || mUpdater == null || ((ExpandableListAdapter) mUpdater) .getGroupCount() == 0) { return; } int state = mUpdater.getHeaderState(groupPosition, childPosition); switch (state) { case ITreeViewHeaderUpdater.STATE_GONE: { mHeaderVisible = false; break; } case ITreeViewHeaderUpdater.STATE_VISIBLE_ALL: { mUpdater.updateHeader(mHeaderView, groupPosition, childPosition, MAX_ALPHA); if (mHeaderView.getTop() != 0) { mHeaderView.layout(0, 0, mHeaderWidth, mHeaderHeight); } mHeaderVisible = true; break; } case ITreeViewHeaderUpdater.STATE_VISIBLE_PART: { // a part of header view visible View firstView = getChildAt(0); int bottom = null != firstView ? firstView.getBottom() : 0; int headerHeight = mHeaderView.getHeight(); int topY; int alpha; if (bottom < headerHeight) { topY = (bottom - headerHeight); alpha = MAX_ALPHA * (headerHeight + topY) / headerHeight; } else { topY = 0; alpha = MAX_ALPHA; } mUpdater.updateHeader(mHeaderView, groupPosition, childPosition, alpha); Log.v("TreeView--updateHeaderView分析：",String.format("bottom=%d,headerHeight=%d,topY=%d,getTop=%d,Header Push up",bottom,headerHeight,topY, mHeaderView.getTop())); if (mHeaderView.getTop() != topY) { mHeaderView.layout(0, topY, mHeaderWidth, mHeaderHeight + topY); } mHeaderVisible = true; break; } } } private void onHeaderViewClick() { long packedPosition = getExpandableListPosition(getFirstVisiblePosition()); int groupPosition = ExpandableListView.getPackedPositionGroup(packedPosition); int status = mUpdater.getHeaderClickStatus(groupPosition); if (ITreeViewHeaderUpdater.STATE_VISIBLE_ALL == status) { collapseGroup(groupPosition); mUpdater.onHeaderClick(groupPosition, ITreeViewHeaderUpdater.STATE_GONE); } else { expandGroup(groupPosition); mUpdater.onHeaderClick(groupPosition, ITreeViewHeaderUpdater.STATE_VISIBLE_ALL); } setSelectedGroup(groupPosition); } }
①、在setHeaderView方法中，调用requestLayout()方法，请求重新布局，该方法执行后，将分别调用onMeasure()、onLayout()和onDraw()方法
②、onMeasuer方法，在该方法中将测量mHeaderView的宽度和高度， 并保存在mHeaderWidth和mHeaderHeight的成员变量中
③、onLayout方法，在该方法中，处理mHeadderView的重新布局问题，当屏幕可见的第一个Group所在位置处的getHeaderState状态改变的时候则重新布局mHeaderView在屏幕的最顶端，并在此方法中调用updateHeaderView方法。
④、updateHeaderView方法， 需要注意的是在此方法中，在STATE_VISIABLE_PART状态中，有段代码如下
if (mHeaderView.getTop() != topY) { mHeaderView.layout(0, topY, mHeaderWidth, mHeaderHeight + topY); }
这段代码起到了到达临界状态时候，起到推送mHeaderView上滑动的作用
⑤、onTouchEvent方法，TreeView中实现该方法，根据事件分发机制适时的捕获用户点击事件，调用onHeaderViewClick方法，起到点击GroupItem以展开和收起对应组的效果。
三、效果图
