为培养手感,最近在前端学习期间,总会学习疯狂Android讲义上的小Demo,用来培养Android手感,以免手生,今天联系ExpandableListView可展开的列表组件,这种效果可以说到处可见了,咋感觉这种效果会有点复杂,,不过只要理清思路,这是相当简单的.下面就讲解一下了:
ExpandableListView是ListView的子类,他可以说是在普通的ListView的基础上进行扩展的,他把应用中的列表项分为几组,每组里又可包含多个列表项.所以说ExpandableListView用法和ListView的用法非常相似,只是ExpandableListView所显示的列表项应该有ExpandableListAdapter提供.ExpandableListAdapter也是一个接口.它和Adapter也是类似的,实现ExpandableListAdapter有3种常用方式.
(1)扩展BaseExpandableListAdapter实现ExpandableListAdapter.
(2)使用SimpleExpandableListAdapter将两个List集合包装成ExpandableListAdapter
(3)使用SimpleCursorTreeAdapter将Cursor中的数据包装成ExpandableListAdapter.
下面就是通过自定义ExpandableListAdapter为ExpandableListView提供列表项,那么先看该Demo的布局文件:
<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" > <ExpandableListView android:id="@+id/list" android:layout_width="match_parent" android:layout_height="wrap_content" /> </LinearLayout> 上面布局就相当简单了,就是在LinearLayout中定义了一个ExpandableListView,下面就是看在程序内怎么进行设置父组件和子组件的,如下: public class MainActivity extends AppCompatActivity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); //创建一个BaseExpandableListAdapter对象 ExpandableListAdapter adapter = new BaseExpandableListAdapter() { int[] logos = new int[]{ R.drawable.p, R.drawable.z, R.drawable.t }; private String[] armTypes = new String[]{ "神族","虫族","人族" }; private String[][] arms = new String[][]{ {"狂战士","龙骑士","黑暗圣堂","电兵"}, {"小狗","刺蛇","飞龙","自爆飞机"}, {"机枪兵","护士MM","幽灵"} }; //获取指定组位置,指定子列表项出的子列表项数据 @Override public Object getChild(int i, int i1) { return arms[i][i1]; } @Override public long getChildId(int i, int i1) { return i1; } @Override public int getChildrenCount(int i) { return arms[i].length; } private TextView getTextView(){ AbsListView.LayoutParams lp = new AbsListView.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,64); TextView textView = new TextView(MainActivity.this); textView.setLayoutParams(lp); textView.setGravity(Gravity.CENTER_VERTICAL | Gravity.LEFT); textView.setPadding(36,0,0,0); textView.setTextSize(20); return textView; } //该方法决定每个子选项的外观 @Override public View getChildView(int i, int i1, boolean b, View view, ViewGroup viewGroup) { TextView textView = getTextView(); textView.setText(getChild(i,i1).toString()); return textView; } //获取指定组位置处的组数据 @Override public Object getGroup(int i) { return armTypes[i]; } @Override public long getGroupId(int i) { return i; } @Override public int getGroupCount() { return armTypes.length; } @Override public View getGroupView(int i, boolean b, View view, ViewGroup viewGroup) { LinearLayout ll = new LinearLayout(MainActivity.this); ll.setOrientation(0); ImageView iv = new ImageView(MainActivity.this); iv.setImageResource(logos[i]); ll.addView(iv); TextView tv = getTextView(); tv.setText(getGroup(i).toString()); ll.addView(tv); return ll; } @Override public boolean hasStableIds() { return true; } @Override public boolean isChildSelectable(int i, int i1) { return true; } }; ExpandableListView expandableListView = (ExpandableListView) findViewById(R.id.list); expandableListView.setAdapter(adapter); } } 看着上面的代码可以看到分别获取组数据,和子数据.,在设置adapter时,我们就是扩展BaseExpandableListAdapter来实现ExpandableListAdapter.在扩展时,关键就是实现4个方法:(1)getGroupCount():该方法返回包含的组列表项的数量.(2)getGroupView():该方法返回的View对象将作为组列表项
(3)getChildrenCount():该方法返回特定组所包含的子列表项的数量.
(4)getChildView():该方法返回的View对象将作为特定组,特定位置的子列表项.
一切完成了,效果图看一下吧:
