Android基础--ListView的显示几种方式

目前常用的ListView显示的方式有三种

【1】BaseAdapter

【2】ArrayAdapter

【3】SimpleAdapter

通过API Code 可以看出，实际上ArrayAdapter,SimpleAdater都是继承了BaseAdapter.所以这里主要讨论BaseAdapter里面的方法。

BaseAdapter的方法主要有四个

【1.1】getCount() //当前数据的总条数

【1.2】getItem(int position) //获取某一项

【1.3】getItemId(int position) //获取某一项的ID

【1.4】getView(int position,View convertView,ViewGroup parent)//生成一个View的视图

若要实现ListView的显示，必须实现 getCount和getView 的方法

首先基于BaseAdapter来显示ListView

主页面布局

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:orientation="vertical"    android:id="@+id/activity_main"    android:layout_width="match_parent"    android:layout_height="match_parent"    tools:context="listview.wineworld.lizhijie.listviewadapter.MainActivity">        <Button        android:text="查询"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:onClick="selectList"        />    <Button        android:text="ArrayAdapter"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:onClick="showArrayAdapter"/>    <Button        android:text="SimpleAdapter"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:onClick="showSimpleAdapter"/>    <ListView        android:id="@+id/lv"        android:layout_width="match_parent"        android:layout_height="match_parent">    </ListView></LinearLayout>

ListView 实际上是有一项一项的数据组成的，那么就需要抽象出来一个item

Item的布局如下

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:id="@+id/item"    android:orientation="horizontal"    android:layout_width="match_parent"    android:layout_height="match_parent">    <TextView        android:id="@+id/name"        android:text="2345645"        android:textColor="#000000"        android:layout_width="0dp"        android:layout_weight="1"        android:layout_height="wrap_content" />    <TextView        android:id="@+id/phone"        android:textColor="#000000"        android:text="2345645"        android:layout_weight="1"        android:layout_width="0dp"        android:layout_height="wrap_content" /></LinearLayout>

MainActivity

    private ListView listView;    private DBHelper dbHelper;    private List<Person> personList;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        dbHelper=new DBHelper(getApplicationContext());        listView=(ListView) findViewById(R.id.lv);        personList=new ArrayList<>();    }      //显示ArrayAdapter    public void showArrayAdapter(View view){        Intent intent=new Intent(getApplicationContext(),ArrayAdapterActivity.class);        startActivity(intent);    }    //显示SimpleAdapter    public void showSimpleAdapter(View view){        Intent intent=new Intent(getApplicationContext(),SimpleAdapterActivity.class);        startActivity(intent);    }    public void selectList(View view){        SQLiteDatabase db=dbHelper.getReadableDatabase();        Cursor cursor= db.query("person",null,null,null,null,null,null);         if(cursor!=null&&cursor.getCount()>0){            while (cursor.moveToNext()){                String name=cursor.getString(1);                String phone=cursor.getString(2);                Person person=new Person();                person.setName(name);                person.setPhone(phone);                personList.add(person);            }            listView.setAdapter(new MyAdapter());        }    }    private class MyAdapter extends BaseAdapter{        @Override        public int getCount() {            return personList.size();        }        @Override        public Object getItem(int i) {            return null;        }        @Override        public long getItemId(int i) {            return 0;        }        @Override        public View getView(int i, View view, ViewGroup viewGroup) {            View newView;            if(view==null){                newView=View.inflate(getApplicationContext(),R.layout.item,null); //打气筒            }else{                newView=view;            }            TextView tv_name=newView.findViewById(R.id.name);            TextView tv_phone=newView.findViewById(R.id.phone);            Person person=personList.get(i);            tv_name.setText(person.getName());            tv_phone.setText(person.getPhone());            return newView;        }    }

【1.2】ArrayAdapter的实现方式

ArrayAdapter 选择构造函数的时候，需要注意你当前显示数据的MODEL,选择构造函数是带MODEL，否则是无法执行getView()方法

布局如下：

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:id="@+id/activity_array_adapter"    android:layout_width="match_parent"    android:layout_height="match_parent"    tools:context="listview.wineworld.lizhijie.listviewadapter.ArrayAdapterActivity">    <ListView        android:id="@+id/array_lv"        android:layout_width="match_parent"        android:layout_height="match_parent"        >    </ListView></LinearLayout>

实现方式

    private List<Person> personList;    private DBHelper dbHelper;    private ListView lv;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_array_adapter);        lv=(ListView)findViewById(R.id.array_lv);        dbHelper=new DBHelper(getApplicationContext());        personList=getPersonList();        if(personList.size()>0){            MyArrayAdapter myArrayAdapter=new MyArrayAdapter(getApplicationContext(),R.layout.item,personList);            lv.setAdapter(myArrayAdapter);        }else{            Toast.makeText(getApplicationContext(),"显示数据失败",Toast.LENGTH_LONG).show();        }    }    private class MyArrayAdapter extends ArrayAdapter<Person> {        //选择构造函数的时候，如果是带类型的，就一定要将MODEL,放入到构造函数中        public MyArrayAdapter(Context context, int resource, List<Person> objects) {            super(context, resource, objects);        }        //重写方法        @Override        public View getView(int position, View convertView, ViewGroup parent) {            View view;            if(convertView==null){                view=View.inflate(getApplicationContext(),R.layout.item,null);//打气筒            }else{                view=convertView;            }            TextView tv_name=view.findViewById(R.id.name);            TextView tv_phone=view.findViewById(R.id.phone);            Person person=personList.get(position);            tv_name.setText(person.getName());            tv_phone.setText(person.getPhone());            return view;        }    }    private List<Person> getPersonList(){        List<Person> list=new ArrayList<>();        SQLiteDatabase db=dbHelper.getReadableDatabase();        Cursor cursor= db.query("person",null,null,null,null,null,null);        if(cursor!=null&&cursor.getCount()>0){            while (cursor.moveToNext()){                String name=cursor.getString(1);                String phone=cursor.getString(2);                Person person=new Person();                person.setName(name);                person.setPhone(phone);                list.add(person);            }        }        return list;    }

【1.3】SimpleAdapter的显示方式比较简单，布局方式与ArrayAdapter是一致的，所以就直接上是实现方式了

    private DBHelper dbHelper;    private ListView lv;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_simple_adapter);        lv=(ListView) findViewById(R.id.simple_lv);        dbHelper=new DBHelper(getApplicationContext());        SimpleAdapter simpleAdapter=new SimpleAdapter(getApplicationContext(),getPersonList(),R.layout.item,              new String[]{"name","phone"},new int[]{R.id.name,R.id.phone});        lv.setAdapter(simpleAdapter);    }    private List<Map<String,String>> getPersonList(){        List<Map<String,String>> mapList=new ArrayList<>();        SQLiteDatabase db=dbHelper.getReadableDatabase();        Cursor cursor= db.query("person",null,null,null,null,null,null);        if(cursor!=null&&cursor.getCount()>0){            while (cursor.moveToNext()){                Map<String,String> map=new HashMap<>();                String name=cursor.getString(1);                String phone=cursor.getString(2);                map.put("name",name);                map.put("phone",phone);                mapList.add(map);            }        }        return mapList;    }

注意的要点：

[1]这个几个适配器实际上都是为了将数据展现在ListView上，都是需要获取每一项数据，来拼接成当前页面的数据。

而，页面手机的可视范围是有限，所以，构造显示的数据的时候。可以将getView()里面的item重复利用。

就是代码中提到的“打气筒"

[2]使用什么适配器，就构造成需要的MODEL.可以直接重写getView()里面的方式，实现具体的业务