ExpandableListView--可展开的列表组件-优快云博客

本文链接：https://blog.youkuaiyun.com/ChatHello/article/details/53519774

本文介绍了Android中可展开的列表组件ExpandableListView的使用，包括其与ListView的关系、用法以及如何通过自定义ExpandableListAdapter来实现列表项。通过扩展BaseExpandableListAdapter、使用SimpleExpandableListAdapter或SimpleCursorTreeAdapter等方式实现ExpandableListAdapter，并详细说明了getGroupView()、getChildrenCount()和getChildView()等关键方法的作用。

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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);
    }
}