Android開發(fā)學(xué)習(xí)教程（18）- Android ListView列表控件用法
—— 如果我這樣就倒下了，那么我也不過是這種程度的男人罷了。 ——索隆
ListView是什么
ListView是一個可以滑動的列表控件，當(dāng)我們需要以列表的方式顯示數(shù)據(jù)時，特別是大量的數(shù)據(jù)時，我們可以使用ListView控件，比如我們常見的通訊錄列表、微信聊天列表、朋友圈列表等。
ListView有什么用
ListView用來展示大量的數(shù)據(jù)列表時具有很好的靈活性和性能，這里需要提到的是，Android還提供了一個更靈活性和更高性能的列表控件RecycleView（這個在后面的篇章會詳細說明）。
ListView怎么用
1. ArrayAdapter
ArrayAdapter專門用來顯示只有一個TextView的數(shù)據(jù)列表項。這點可以從ArrayAdapter的源碼看出來。這里截取其中一小段說明：
1
2
3
4
5
6
7
8
final?TextView text;if?(mFieldId ==?0) {????// 如果沒有指定顯示數(shù)據(jù)的控件，那就把整個布局view轉(zhuǎn)換成TextView????text = (TextView) view;}?else?{????// 如果有指定，那就實例化????text = view.findViewById(mFieldId);}我們來看ArrayAdapter的具體用法，新建activity_main.xml:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
<?xml?version="1.0"?encoding="utf-8"?><androidx.constraintlayout.widget.ConstraintLayout?xmlns:android="http://schemas.android.com/apk/res/android"????xmlns:tools="http://schemas.android.com/tools"????android:layout_width="match_parent"????android:layout_height="match_parent"????tools:context=".MainActivity">????<ListView????????android:id="@+id/listview"????????android:layout_width="match_parent"????????android:layout_height="match_parent"????????android:divider="#EEEEEE"????????android:dividerHeight="1dp"?/></androidx.constraintlayout.widget.ConstraintLayout>然后在MainActivity中實例化：
1
ListView listView = (ListView) findViewById(R.id.listview);實例化了ListView之后給ListView裝載數(shù)據(jù)，即實例化數(shù)據(jù)適配器Aadapter：
1
2
3
4
????String[] data = {"趙一",?"劉二",?"張三",?"李四",?"王五",?"趙六",?"韓梅梅",?"李雷",?"小明",?"小紅",?"小張",?"小趙",?"小劉",?"小往",?"小韓",?"小李",?"小孫",?"小錢"};????ArrayAdapter<string> array =?new?ArrayAdapter<>(this, android.R.layout.simple_list_item_1, data);????listView.setAdapter(array);</string>運行看效果：
2. SimpleAdapter
SimpleAdapter相對于ArrayAdpter展示只有一個TextView的數(shù)據(jù)列表項多了ImageView的數(shù)據(jù)列表項。這個看源碼也可以看得出。這里截取其中一小段說明：
1
2
3
4
5
6
7
8
9
10
11
if?(v?instanceof?TextView) {????// Note: keep the instanceof TextView check at the bottom of these????// ifs since a lot of views are TextViews (e.g. CheckBoxes).????setViewText((TextView) v, text);}?else?if?(v?instanceof?ImageView) {????if?(data?instanceof?Integer) {????????setViewImage((ImageView) v, (Integer) data);????}?else?{????????setViewImage((ImageView) v, text);????}}我們來看SimpleAdapter的具體用法，修改MainActivity代碼為：
1
2
3
4
5
6
7
8
9
10
????ArrayList<map<string, string="">> list =?new?ArrayList<>();????Map<string, string=""> hashMap =?null;????for?(int?i =?0; i <?20; i++) {????????hashMap =?new?HashMap<>();????????hashMap.put("name",?"第"?+ i +?"個item");????????list.add(hashMap);????}????SimpleAdapter simple =?new?SimpleAdapter(this, list, R.layout.item_listview,?new?String[]{"name"},?new?int[]{R.id.tv_name});????listView.setAdapter(simple);</string,></map<string,>運行效果：
3. 自定義BaseAdaper
自定義BaseAdapter可以展示任意類型的數(shù)據(jù)列表項，其實上面SimpleAdapter和ArrayAdapter都是繼承自BaseAdapter，區(qū)別在于getView方法，SimpleAdapter和ArrayAdapter的getView讀者可以自行查看源碼，基本和上面截取的一小段差不多。我們來看自定義BaseAdapter的用法：
1
2
3
4
5
6
????List<string> list =?new?ArrayList<>();????for?(int?i =?0; i <?20; i++) {??????????list..add("第"?+ i +?"個item");????}????listView.setAdapter(new?MyAdapter(list));</string>其中MyAdapter類的代碼如下：
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
????class?MyAdapter?extends?BaseAdapter {????????????private?List<string> mList;????????????public?MyAdapter(List<string> mList) {????????????????this.mList = mList;????????????}????????????@Override????????????public?int?getCount() {????????????????return?mList ==?null???0?: mList.size();????????????}????????????@Override????????????public?String getItem(int?position) {????????????????return?mList.get(position);????????????}????????????@Override????????????public?long?getItemId(int?position) {????????????????return?position;????????????}????????????@Override????????????public?View getView(int?position, View convertView, ViewGroup parent) {????????????????ViewHolder holder =?null;????????????????//判斷是否緩存????????????????if?(convertView ==?null) {????????????????holder =?new?ViewHolder();????????????????//通過LayoutInflater實例化布局????????????????convertView = mInflater.inflate(R.layout.item_listview,?null);????????????????holder.tvName = (TextView) convertView.findViewById(R.id.tv_name);????????????????convertView.setTag(holder);????????????????}?else?{????????????????//通過tag找到緩存的布局????????????????holder = (ViewHolder) convertView.getTag();????????????????}????????????????//設(shè)置布局中控件要顯示的視圖????????????????holder.tvName.setText(mList.get(position));????????????????return?convertView;????????????}????????????public?final?class?ViewHolder {????????????????public?TextView tvName;????????????}????????}????}</string></string>運行效果：
源碼鏈接：https://yunjunet.cn/876782.html
標簽：
