android - ExpandableListView 中的固定组

Question

是否有一种标准方法可以在滚动组项目时将组项目固定到屏幕顶部。我在 ListView 中看到了类似的例子。我应该实现哪些接口(interface)或覆盖哪些方法？

Answer 1

我找到了基于 Pinned Header ListView 的解决方案Peter Kuterna 和 android 示例 ExpandableList1.java。PinnedHeaderExpListView.java

package com.example;

import com.example.ExpandableList.MyExpandableListAdapter;

import android.content.Context;
import android.graphics.Canvas;
import android.util.AttributeSet;
import android.view.View;
import android.widget.BaseExpandableListAdapter;
import android.widget.ExpandableListAdapter;
import android.widget.ExpandableListView;
import android.widget.TextView;

/**
 * A ListView that maintains a header pinned at the top of the list. The
 * pinned header can be pushed up and dissolved as needed.
 */
public class PinnedHeaderExpListView extends ExpandableListView{

    /**
     * Adapter interface.  The list adapter must implement this interface.
     */
    public interface PinnedHeaderAdapter {

        /**
         * Pinned header state: don't show the header.
         */
        public static final int PINNED_HEADER_GONE = 0;

        /**
         * Pinned header state: show the header at the top of the list.
         */
        public static final int PINNED_HEADER_VISIBLE = 1;

        /**
         * Pinned header state: show the header. If the header extends beyond
         * the bottom of the first shown element, push it up and clip.
         */
        public static final int PINNED_HEADER_PUSHED_UP = 2;

        /**
         * Configures the pinned header view to match the first visible list item.
         *
         * @param header pinned header view.
         * @param position position of the first visible list item.
         * @param alpha fading of the header view, between 0 and 255.
         */
        void configurePinnedHeader(View header, int position, int alpha);
    }

    private static final int MAX_ALPHA = 255;

    private MyExpandableListAdapter mAdapter;
    private View mHeaderView;
    private boolean mHeaderViewVisible;

    private int mHeaderViewWidth;

    private int mHeaderViewHeight;

    public PinnedHeaderExpListView(Context context) {
        super(context);
    }

    public PinnedHeaderExpListView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public PinnedHeaderExpListView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
    }

    public void setPinnedHeaderView(View view) {
        mHeaderView = view;

        // Disable vertical fading when the pinned header is present
        // TODO change ListView to allow separate measures for top and bottom fading edge;
        // in this particular case we would like to disable the top, but not the bottom edge.
        if (mHeaderView != null) {
            setFadingEdgeLength(0);
        }
        requestLayout();
    }

    @Override
    public void setAdapter(ExpandableListAdapter adapter) {
        super.setAdapter(adapter);
        mAdapter = (MyExpandableListAdapter)adapter;
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        if (mHeaderView != null) {
            measureChild(mHeaderView, widthMeasureSpec, heightMeasureSpec);
            mHeaderViewWidth = mHeaderView.getMeasuredWidth();
            mHeaderViewHeight = mHeaderView.getMeasuredHeight();
        }
    }

    @Override
    protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
        super.onLayout(changed, left, top, right, bottom);
        if (mHeaderView != null) {
            mHeaderView.layout(0, 0, mHeaderViewWidth, mHeaderViewHeight);
            configureHeaderView(getFirstVisiblePosition());
        }
    }

    /** 
     * animating header pushing
     * @param position
     */
    public void configureHeaderView(int position) {
        final int group = getPackedPositionGroup(getExpandableListPosition(position));
        int groupView = getFlatListPosition(getPackedPositionForGroup(group));

        if (mHeaderView == null) {
            return;
        }

        mHeaderView.setOnClickListener(new OnClickListener() {

            public void onClick(View header) {
                if(!expandGroup(group)) collapseGroup(group); 
            }
        }); 

        int state,nextSectionPosition = getFlatListPosition(getPackedPositionForGroup(group+1));

        if (mAdapter.getGroupCount()== 0) {
            state = PinnedHeaderAdapter.PINNED_HEADER_GONE;
        }else if (position < 0) {
            state = PinnedHeaderAdapter.PINNED_HEADER_GONE;
        }else if (nextSectionPosition != -1 && position == nextSectionPosition - 1) {
            state=PinnedHeaderAdapter.PINNED_HEADER_PUSHED_UP;
        }else  state=PinnedHeaderAdapter.PINNED_HEADER_VISIBLE;

        switch (state) {    
            case PinnedHeaderAdapter.PINNED_HEADER_GONE: {
                mHeaderViewVisible = false;
                break;
            }

            case PinnedHeaderAdapter.PINNED_HEADER_VISIBLE: {
                mAdapter.configurePinnedHeader(mHeaderView, group, MAX_ALPHA);
                if (mHeaderView.getTop() != 0) {
                    mHeaderView.layout(0, 0, mHeaderViewWidth, mHeaderViewHeight);
                }
                mHeaderViewVisible = true;
                break;
            }

            case PinnedHeaderAdapter.PINNED_HEADER_PUSHED_UP: {
                View firstView = getChildAt(0);
                if(firstView==null){
                    if (mHeaderView.getTop() != 0) {
                        mHeaderView.layout(0, 0, mHeaderViewWidth, mHeaderViewHeight);
                    }
                    mHeaderViewVisible = true;
                    break;
                }
                int bottom = firstView.getBottom();
                int itemHeight = firstView.getHeight();
                int headerHeight = mHeaderView.getHeight();
                int y;
                int alpha;
                if (bottom < headerHeight) {
                    y = (bottom - headerHeight);
                    alpha = MAX_ALPHA * (headerHeight + y) / headerHeight;
                } else {
                    y = 0;
                    alpha = MAX_ALPHA;
                }
                mAdapter.configurePinnedHeader(mHeaderView, group, alpha);
                //выползание
                if (mHeaderView.getTop() != y) {
                    mHeaderView.layout(0, y, mHeaderViewWidth, mHeaderViewHeight + y);
                }
                mHeaderViewVisible = true;
                break;
            }
        }
    }

    @Override
    protected void dispatchDraw(Canvas canvas) {
        super.dispatchDraw(canvas);
        if (mHeaderViewVisible) {
            drawChild(canvas, mHeaderView, getDrawingTime());
        }
    }

}

可扩展列表.java

package com.example;


import android.app.Activity;
import android.graphics.Color;
import android.os.Bundle;
import android.view.Gravity;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AbsListView;
import android.widget.AbsListView.LayoutParams;
import android.widget.AbsListView.OnScrollListener;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.BaseExpandableListAdapter;
import android.widget.ExpandableListAdapter;
import android.widget.SectionIndexer;
import android.widget.TextView;
import android.widget.Toast;

import com.example.PinnedHeaderExpListView.PinnedHeaderAdapter;



/**
 * Demonstrates expandable lists using a custom {@link ExpandableListAdapter}
 * from {@link BaseExpandableListAdapter}.
 */
public class ExpandableList extends Activity {

    MyExpandableListAdapter mAdapter;
    PinnedHeaderExpListView elv;

    private int mPinnedHeaderBackgroundColor;
    private int mPinnedHeaderTextColor;

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        // Set up our adapter
        mAdapter = new MyExpandableListAdapter();
        elv = (PinnedHeaderExpListView) findViewById(R.id.list);

        elv.setAdapter(mAdapter);

        mPinnedHeaderBackgroundColor = getResources().getColor(android.R.color.black);
        mPinnedHeaderTextColor = getResources().getColor(android.R.color.white);

        elv.setGroupIndicator(null);
        View h = LayoutInflater.from(this).inflate(R.layout.header, (ViewGroup) findViewById(R.id.root), false);
        elv.setPinnedHeaderView(h);
        elv.setOnScrollListener((OnScrollListener) mAdapter);
        elv.setDividerHeight(0);
    }

    /**
     * A simple adapter which maintains an ArrayList of photo resource Ids. 
     * Each photo is displayed as an image. This adapter supports clearing the
     * list of photos and adding a new photo.
     *
     */
    public class MyExpandableListAdapter extends BaseExpandableListAdapter implements PinnedHeaderAdapter, OnScrollListener{
        // Sample data set.  children[i] contains the children (String[]) for groups[i].
        private String[] groups = { "People Names", "Dog Names", "Cat Names", "Fish Names" };
        private String[][] children = {
                { "Arnold", "Barry", "Chuck", "David", "Stas", "Oleg", "Max","Alex","Romeo", "Adolf" },
                { "Ace", "Bandit", "Cha-Cha", "Deuce", "Nokki", "Baron", "Sharik", "Toshka","SObaka","Belka","Strelka","Zhuchka"},
                { "Fluffy", "Snuggles","Cate", "Yasha","Bars" },
                { "Goldy", "Bubbles","Fluffy", "Snuggles","Guffy", "Snoopy" }
        };

        public Object getChild(int groupPosition, int childPosition) {
            return children[groupPosition][childPosition];
        }

        public long getChildId(int groupPosition, int childPosition) {
            return childPosition;
        }

        public int getChildrenCount(int groupPosition) {
            return children[groupPosition].length;
        }

        public TextView getGenericView() {
            // Layout parameters for the ExpandableListView
            AbsListView.LayoutParams lp = new AbsListView.LayoutParams(
                    ViewGroup.LayoutParams.MATCH_PARENT, 64);

            TextView textView = new TextView(ExpandableList.this);
            textView.setLayoutParams(lp);
            // Center the text vertically
            textView.setGravity(Gravity.CENTER_VERTICAL | Gravity.LEFT);
            // Set the text starting position
            textView.setPadding(36, 0, 0, 0);
            return textView;
        }

        public View getChildView(int groupPosition, int childPosition, boolean isLastChild,
                View convertView, ViewGroup parent) {
            TextView textView = getGenericView();
            textView.setText(getChild(groupPosition, childPosition).toString());
            return textView;
        }


        public Object getGroup(int groupPosition) {
            return groups[groupPosition];
        }

        public int getGroupCount() {
            return groups.length;
        }

        public long getGroupId(int groupPosition) {
            return groupPosition;
        }

        public View getGroupView(int groupPosition, boolean isExpanded, View convertView,
                ViewGroup parent) {
            TextView textView = (TextView) LayoutInflater.from(getApplicationContext()).inflate(R.layout.header, parent, false);
            textView.setText(getGroup(groupPosition).toString());
            return textView;
        }

        public boolean isChildSelectable(int groupPosition, int childPosition) {
            return true;
        }

        public boolean hasStableIds() {
            return true;
        }


        /**
         * размытие/пропадание хэдера
         */
        public void configurePinnedHeader(View v, int position, int alpha) {
            TextView header = (TextView) v;
            final String title = (String) getGroup(position);

            header.setText(title);
            if (alpha == 255) {
                header.setBackgroundColor(mPinnedHeaderBackgroundColor);
                header.setTextColor(mPinnedHeaderTextColor);
            } else {
                header.setBackgroundColor(Color.argb(alpha, 
                        Color.red(mPinnedHeaderBackgroundColor),
                        Color.green(mPinnedHeaderBackgroundColor),
                        Color.blue(mPinnedHeaderBackgroundColor)));
                header.setTextColor(Color.argb(alpha, 
                        Color.red(mPinnedHeaderTextColor),
                        Color.green(mPinnedHeaderTextColor),
                        Color.blue(mPinnedHeaderTextColor)));
            }
        }

        public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
            if (view instanceof PinnedHeaderExpListView) {
                ((PinnedHeaderExpListView) view).configureHeaderView(firstVisibleItem);
            }

        }

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

        }

    }

}

主.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/root"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

    <view class="com.example.PinnedHeaderExpListView"
        android:id="@+id/list"
        android:layout_width="match_parent"
        android:layout_height="match_parent" /> 

</LinearLayout>

标题.xml

<?xml version="1.0" encoding="utf-8"?>
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/header"
    android:layout_width="match_parent"
    android:layout_height="25dp"
    android:background="@android:color/black" >

</TextView>

它按预期工作，除了单击标题。我希望点击标题将等于点击组项目，但事件甚至没有发生并且 OnClickListener 没有得到控制。为什么？

编辑:如果您在 ExpandableList.java Activity 的 onCreate() 方法中添加以下代码，则单击标题也有效。

        elv.setOnGroupClickListener(new OnGroupClickListener() {

        @Override
        public boolean onGroupClick(ExpandableListView parent, View v,
                int groupPosition, long id) {
            return false;
        }
    });