ListView的HeaderView包含的GridView滑动隐藏后无法点击问题分析

1 现象

碰到一个奇怪问题, 就是ListView的HeaderView中有一个GridView, 刚加载页面时可以点击,滑动隐藏HeaderView后重新显示的GridView就不可以点击了,如果GridView作为HeaderView就没有这个问题。
demo如下:

package com.example.gridview;

import android.content.Context;
import android.os.Bundle;
import android.util.AttributeSet;
import android.view.Gravity;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.BaseAdapter;
import android.widget.GridView;
import android.widget.LinearLayout;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;

import androidx.annotation.Nullable;

import com.example.base.BaseActivity;
import com.example.utils.StringUtils;

public class GridViewActivity extends BaseActivity {


    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);


        ListView listView = new ListView(this);
        StringAdapter gridItemAdapter = new StringAdapter(this, 50);
        gridItemAdapter.setPrefix("listView");
        listView.setAdapter(gridItemAdapter);


        LinearLayout linearLayout = new LinearLayout(this);
        linearLayout.setOrientation(LinearLayout.VERTICAL);
        HeaderGridView headerView = new HeaderGridView(this);
        headerView.setNumColumns(4);
        StringAdapter adapter = new StringAdapter(this);
        adapter.setPrefix("header");
        headerView.setAdapter(adapter);
        headerView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                Toast.makeText(GridViewActivity.this, "点击了GridView, 第" + position + "项", Toast.LENGTH_SHORT).show();
            }
        });
        linearLayout.addView(headerView);


        if (headerView.getParent() == null) {
            listView.addHeaderView(headerView);
        } else {
            listView.addHeaderView(linearLayout);
        }
        listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                Toast.makeText(GridViewActivity.this, "点击了ListView, 第" + position + "项", Toast.LENGTH_SHORT).show();
            }
        });
        setContentView(listView);
    }

    private static class StringAdapter extends BaseAdapter {


        private final int count;
        private Context context;

        private String prefix = null;

        private StringAdapter(Context context) {
            this.context = context;
            this.count = 5;
        }

        private StringAdapter(Context context, int count) {
            this.context = context;
            this.count = count;
        }

        public void setPrefix(String prefix) {
            this.prefix = prefix;
        }

        @Override
        public int getCount() {
            return count;
        }

        @Override
        public String getItem(int position) {
            return String.valueOf((char) ('a' + position));
        }

        @Override
        public long getItemId(int position) {
            return position;
        }

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

            TextView temp;
            if (convertView instanceof TextView) {
                temp = (TextView) convertView;
            } else {
                temp = new TextView(context);
                convertView = temp;
            }
            int padding = StringUtils.dipToPx(20);
            temp.setPadding(padding, padding, padding, padding);
            temp.setGravity(Gravity.CENTER);

            temp.setText(prefix + getItem(position));
            return convertView;
        }
    }

    public static class HeaderGridView extends GridView {

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

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

    }

    public static class DebugListView extends ListView {

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

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

        @Override
        protected void onAttachedToWindow() {
            super.onAttachedToWindow();
        }

        @Override
        protected void layoutChildren() {
            super.layoutChildren();
        }
    }
}

2 问题分析

2.1 滑动前

在OnItemClickListener监听中打个断点, 可以看出对应的调用栈为:

依次点击各个调用的方法, 可以看出最终是AbsListView.PerformClick类的实例performClick处理了相关点击事件,具体逻辑可查看AbsListView.PerformClick类。

performClick.run()方法执行只在AbsListViw的onTouchUp方法中,

2.2 滑动后

onTouchUp方法中打个断点, 发现mDataChanged属性为true,无法再往下走,不会执行performClick.run()方法,也就不会触发OnItemClick事件。

2.3 mDataChanged赋值为true的位置

在AbsListView类的所有mDataChanged赋值为true的地方打断点,再执行滑动操作,断点停留在如下位置:

也就是说AbsListView重新显示的时候将mDataChanged置为true
调用栈如下:

其中makeAndAddView、setupChild、addViewInLayout、addViewInner表示重建View并将View添加到ListView。addViewInner中部分代码如下:

child就是LinearLayout, GridView的父类, ListView的HeaderView, child执行dispatchAttachedToWindow方法,将自身以及子View添加到窗口上,于是GridView执行了onAttachedToWindow方法, 导致mDataChanges被置为true, OnItemClick事件无法执行。

2.3 GridView直接作为ListView的HeaderView为什么可以滑动

GridView直接作为ListView的HeaderView滑动后为什么可以点击?
去掉linearLayout.addView(headerView)
在GridView、AbsListView、AdapterView中mDataChanged赋值为false的地方打断点,方法调用栈如下:

具体代码:

可以看出单独的GridView作为HeaderView重新显示后会调用layoutChildren进行布局, 将mDataChanged置为false从而在滑动隐藏再显示后可以响应点击事件。

2.4 ListView setupChild分析

setupChild是ListView显示某一个View时执行的逻辑,进行了测量、布局等等操作,GridView单独作为一个View时会触发layoutChildren, 如果作为LinearLayout的子View,LinearLayout的测量、布局等操作不会导致GridView重新布局。

3 解决方法

重写GridView, 在onAttachedToWindow方法中调用adapter的notifyDataSetChanged();

    public static class HeaderGridView extends GridView {

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

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

        @Override
        protected void onAttachedToWindow() {
            super.onAttachedToWindow();
            ListAdapter adapter = getAdapter();
            if (adapter instanceof BaseAdapter) {
                ((BaseAdapter) adapter).notifyDataSetChanged();
            }
        }
    }
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