ExpandableListView打造带折叠动画效果的多条目展示框架

package com.huyingzi.animatedexpandablelistviewdemo.view; import android.annotation.SuppressLint; import android.content.Context; import android.graphics.Canvas; import android.graphics.drawable.Drawable; import android.os.Build; import android.util.AttributeSet; import android.util.SparseArray; import android.view.View; import android.view.ViewGroup; import android.view.animation.Animation; import android.view.animation.Animation.AnimationListener; import android.view.animation.Transformation; import android.widget.AbsListView; import android.widget.BaseExpandableListAdapter; import android.widget.ExpandableListAdapter; import android.widget.ExpandableListView; import java.util.ArrayList; import java.util.List; /** * This class defines an ExpandableListView which supports animations for collapsing and expanding groups. * 这个类扩展了ExpandableListView 增加了折叠动画 */ public class AnimatedExpandableListView extends ExpandableListView { /* * A detailed explanation for how this class works: * * Animating the ExpandableListView was no easy task. * The way that this class does it is by exploiting how an ExpandableListView works. * Normally when {@link ExpandableListView#collapseGroup(int)} or * {@link ExpandableListView#expandGroup(int)} is called, the view toggles * the flag for a group and calls notifyDataSetChanged to cause the ListView * to refresh all of it's view. This time however, depending on whether a * group is expanded or collapsed, certain childViews will either be ignored * or added to the list. * * Knowing this, we can come up with a way to animate our views. For * instance for group expansion, we tell the adapter to animate the * children of a certain group. We then expand the group which causes the * ExpandableListView to refresh all views on screen. The way that * ExpandableListView does this is by calling getView() in the adapter. * However since the adapter knows that we are animating a certain group, * instead of returning the real views for the children of the group being * animated, it will return a fake dummy view. This dummy view will then * draw the real child views within it's dispatchDraw function. The reason * we do this is so that we can animate all of it's children by simply * animating the dummy view. After we complete the animation, we tell the * adapter to stop animating the group and call notifyDataSetChanged. Now * the ExpandableListView is forced to refresh it's views again, except this * time, it will get the real views for the expanded group. * * So, to list it all out, when {@link #expandGroupWithAnimation(int)} is * called the following happens: * * 1. The ExpandableListView tells the adapter to animate a certain group. * 2. The ExpandableListView calls expandGroup. * 3. ExpandGroup calls notifyDataSetChanged. * 4. As an result, getChildView is called for expanding group. * 5. Since the adapter is in "animating mode", it will return a dummy view. * 6. This dummy view draws the actual children of the expanding group. * 7. This dummy view's height is animated from 0 to it's expanded height. * 8. Once the animation completes, the adapter is notified to stop * animating the group and notifyDataSetChanged is called again. * 9. This forces the ExpandableListView to refresh all of it's views again. * 10.This time when getChildView is called, it will return the actual * child views. * * For animating the collapse of a group is a bit more difficult since we * can't call collapseGroup from the start as it would just ignore the * child items, giving up no chance to do any sort of animation. Instead * what we have to do is play the animation first and call collapseGroup * after the animation is done. * * So, to list it all out, when {@link #collapseGroupWithAnimation(int)} is * called the following happens: * * 1. The ExpandableListView tells the adapter to animate a certain group. * 2. The ExpandableListView calls notifyDataSetChanged. * 3. As an result, getChildView is called for expanding group. * 4. Since the adapter is in "animating mode", it will return a dummy view. * 5. This dummy view draws the actual children of the expanding group. * 6. This dummy view's height is animated from it's current height to 0. * 7. Once the animation completes, the adapter is notified to stop * animating the group and notifyDataSetChanged is called again. * 8. collapseGroup is finally called. * 9. This forces the ExpandableListView to refresh all of it's views again. * 10.This time when the ListView will not get any of the child views for * the collapsed group. */ @SuppressWarnings("unused") private static final String TAG = AnimatedExpandableListAdapter.class.getSimpleName(); /** * The duration of the expand/collapse animations */ private static final int ANIMATION_DURATION = 300; private AnimatedExpandableListAdapter adapter; public AnimatedExpandableListView(Context context) { super(context); } public AnimatedExpandableListView(Context context, AttributeSet attrs) { super(context, attrs); } public AnimatedExpandableListView(Context context, AttributeSet attrs, int defStyle) { super(context, attrs, defStyle); } /** * @see ExpandableListView#setAdapter(ExpandableListAdapter) */ public void setAdapter(ExpandableListAdapter adapter) { super.setAdapter(adapter); // Make sure that the adapter extends AnimatedExpandableListAdapter // if(adapter instanceof AnimatedExpandableListAdapter) { this.adapter = (AnimatedExpandableListAdapter) adapter; this.adapter.setParent(this); } else { throw new ClassCastException(adapter.toString() + " must implement AnimatedExpandableListAdapter"); } } /** * Expands the given group with an animation. * @param groupPos The position of the group to expand * @return Returns true if the group was expanded. False if the group was * already expanded. */ @SuppressLint("NewApi") public boolean expandGroupWithAnimation(int groupPos) { boolean lastGroup = groupPos == adapter.getGroupCount() - 1; if (lastGroup && Build.VERSION.SDK_INT >= Build.VERSION_CODES.ICE_CREAM_SANDWICH) { return expandGroup(groupPos, true); } int groupFlatPos = getFlatListPosition(getPackedPositionForGroup(groupPos)); if (groupFlatPos != -1) { int childIndex = groupFlatPos - getFirstVisiblePosition(); if (childIndex < getChildCount()) { // Get the view for the group is it is on screen... View v = getChildAt(childIndex); if (v.getBottom() >= getBottom()) { // If the user is not going to be able to see the animation // we just expand the group without an animation. // This resolves the case where getChildView will not be // called if the children of the group is not on screen // We need to notify the adapter that the group was expanded // without it's knowledge adapter.notifyGroupExpanded(groupPos); return expandGroup(groupPos); } } } // Let the adapter know that we are starting the animation... adapter.startExpandAnimation(groupPos, 0); // Finally call expandGroup (note that expandGroup will call // notifyDataSetChanged so we don't need to) return expandGroup(groupPos); } /** * Collapses the given group wit