Android之ExpandableList扩展用法(基于BaseExpandableListAdapter)
1.简介
基于基于BaseExpandableListAdapter扩展的ExpandableList用法,现在网上流行的主要有两种:第一种是向BaseExpandableListAdapter传入两个数组,第一个是表示Group(目录头)信息的一维数组,第二个是表示Child(目录子项)的二维数组数组;第二种是构建两个类,一个是表示目录信息的GroupInfo类,另一个是表示子项信息的ChildInfo类,然后传入BaseExpandableListAdapter。通过对比发现,第一种方法由于数组是固定的,而实际项目中往往需要动态变化的目录和子项,因此用处不大,第二种方法文件太多,实现复杂。这里提供一种方法,传递两个个动态的二维数组来实现目录结构。
2.案例
package com.devin; import java.util.ArrayList; import android.app.Activity; import android.graphics.Color; import android.graphics.drawable.ColorDrawable; import android.os.Bundle; import android.view.Gravity; import android.view.View; import android.view.View.OnClickListener; import android.view.ViewGroup; import android.widget.BaseExpandableListAdapter; import android.widget.ExpandableListAdapter; import android.widget.ExpandableListView; import android.widget.ImageView; import android.widget.LinearLayout; import android.widget.TextView; public class PadTestActivity extends Activity { protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); ArrayList<String> groupList = new ArrayList<String>(); for (int i = 0; i < 3; i++) { groupList.add("title"); } ArrayList<String> itemList1 = new ArrayList<String>(); itemList1.add("Item1"); itemList1.add("Item2"); ArrayList<String> itemList2 = new ArrayList<String>(); itemList2.add("Item1"); itemList2.add("Item21"); itemList2.add("Item3"); ArrayList<String> itemList3 = new ArrayList<String>(); itemList3.add("Item1"); itemList3.add("Item2"); itemList3.add("Item3"); itemList3.add("Item4"); ArrayList<ArrayList<String>> childList = new ArrayList<ArrayList<String>>(); childList.add(itemList1); childList.add(itemList2); childList.add(itemList3); ExpandableListView list = new ExpandableListView(this); ExpandableListAdapter mAdapter = new MyExpandableListAdapter(groupList, childList); list.setAdapter(mAdapter); list.setCacheColorHint(0x00000000); list.setSelector(new ColorDrawable(Color.TRANSPARENT)); list.setGroupIndicator(null); for (int i = 0; i < mAdapter.getGroupCount(); i++) { list.expandGroup(i); } setContentView(list); } private class MyExpandableListAdapter extends BaseExpandableListAdapter { private ArrayList<String> groupList; private ArrayList<ArrayList<String>> childList; MyExpandableListAdapter(ArrayList<String> groupList, ArrayList<ArrayList<String>> childList) { this.groupList = groupList; this.childList = childList; } public Object getChild(int groupPosition, int childPosition) { return childList.get(groupPosition).get(childPosition); } private int selectedGroupPosition = -1; private int selectedChildPosition = -1; public void setSelectedPosition(int selectedGroupPosition, int selectedChildPosition) { this.selectedGroupPosition = selectedGroupPosition; this.selectedChildPosition = selectedChildPosition; } public long getChildId(int groupPosition, int childPosition) { return childPosition; } public int getChildrenCount(int groupPosition) { return childList.get(groupPosition).size(); } public View getChildView(final int groupPosition, final int childPosition, boolean isLastChild, View convertView, ViewGroup parent) { TextView textView = null; if (convertView == null) { textView = new TextView(PadTestActivity.this); textView.setPadding(32, 10, 0, 10); convertView = textView; } else { textView = (TextView) convertView; } textView.setText(getChild(groupPosition, childPosition).toString()); if (groupPosition == selectedGroupPosition) { if (childPosition == selectedChildPosition) { textView.setBackgroundColor(0xffb6ddee); } else { textView.setBackgroundColor(Color.TRANSPARENT); } } textView.setOnClickListener(new OnClickListener() { public void onClick(View v) { setSelectedPosition(groupPosition, childPosition); notifyDataSetChanged(); } }); return textView; } public Object getGroup(int groupPosition) { return groupList.get(groupPosition); } public int getGroupCount() { return groupList.size(); } public long getGroupId(int groupPosition) { return groupPosition; } public View getGroupView(int groupPosition, boolean isExpanded, View convertView, ViewGroup parent) { LinearLayout cotain = new LinearLayout(PadTestActivity.this); cotain.setPadding(0, 10, 0, 10); cotain.setGravity(Gravity.CENTER_VERTICAL); ImageView imgIndicator = new ImageView(PadTestActivity.this); TextView textView = new TextView(PadTestActivity.this); textView.setText(getGroup(groupPosition).toString()); textView.setPadding(5, 0, 0, 0); if (isExpanded) { imgIndicator.setBackgroundResource(R.drawable.macro_minus); } else { imgIndicator.setBackgroundResource(R.drawable.macro_plus); } cotain.addView(imgIndicator); cotain.addView(textView); return cotain; } public boolean hasStableIds() { return true; } public boolean isChildSelectable(int groupPosition, int childPosition) { return true; } } }
上述代码中,过向BaseExpandableListAdapter传递两个动态数组groupList(表示目录头信息)和childList (表示子项信息)来构建目录,一方面能够实现动态的添加数据,另一方面简化了实现,一举两得。另外,重写的BaseExpandableListAdapter,如果应用在实际项目中,需要对getGroupView()和getChildView()方法进行构建缓存(和ListView构建一样),以便优化性能和防止内存泄漏。需要的朋友可以自己构建。