Android学习笔记_11_ListView控件使用
一、界面设计：
1、activity_main.xml文件：
<RelativeLayout 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" android:paddingBottom="@dimen/activity_vertical_margin" android:paddingLeft="@dimen/activity_horizontal_margin" android:paddingRight="@dimen/activity_horizontal_margin" android:paddingTop="@dimen/activity_vertical_margin" tools:context=".MainActivity" > <LinearLayout android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="horizontal" > <TextView android:layout_width="120dp" android:layout_height="wrap_content" android:text="@string/name" /> <TextView android:layout_width="match_parent" android:layout_height="wrap_content" android:text="@string/age" /> </LinearLayout> <ListView android:id="@+id/listView" android:layout_width="match_parent" android:layout_height="match_parent" android:layout_marginTop="20dp" > </ListView> </RelativeLayout>
2、item.xml文件：用于显示每一行的内容
<?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="horizontal" > <TextView android:id="@+id/name" android:layout_width="120dp" android:layout_height="wrap_content" /> <TextView android:id="@+id/age" android:layout_width="match_parent" android:layout_height="wrap_content" /> </LinearLayout>
3、最终测试界面：
每行显示用户名称和年龄。
二、三种方式将数据绑定到ListView控件上：
package com.example.listview; import java.util.ArrayList; import java.util.HashMap; import java.util.List; import android.app.Activity; import android.database.Cursor; import android.os.Bundle; import android.support.v4.widget.SimpleCursorAdapter; import android.view.Menu; import android.view.View; import android.widget.AdapterView; import android.widget.AdapterView.OnItemClickListener; import android.widget.ListView; import android.widget.SimpleAdapter; import android.widget.Toast; import com.example.entity.Person; import com.example.lservice.DBPersonService; import com.example.lservice.PersonAdapter; public class MainActivity extends Activity { private ListView listView; private DBPersonService personService; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); listView = (ListView) this.findViewById(R.id.listView); personService = new DBPersonService(this); //监听行点击事件
listView.setOnItemClickListener(new OnItemClickListener() { //parent:指当前被点击条目的listview view：指当前被点击的条目 position:被点击条目的索引 @Override public void onItemClick(AdapterView<?> parent, View view, int position, long id) { ListView lv = (ListView) parent; /* * 1、自定义适配器当前条目是Person对象。 * 2、采用SimpleCursorAdapter适配器，返回的是Cursor对象。 * 3、采用SimpleAdapter适配器，返回的是HashMap<String, Object>对象。 */ Person p = (Person) lv.getItemAtPosition(position); String info = p.getName() + " " + position + " " + id; Toast.makeText(getApplicationContext(), info, 1).show(); } }); show3(); } //第一种： 使用SimpleAdapter作为适配器 private void show() { List<Person> persons = personService.getScrollData(0, 20); List<HashMap<String, Object>> data = new ArrayList<HashMap<String, Object>>(); for (Person person : persons) { HashMap<String, Object> map = new HashMap<String, Object>(); map.put("name", person.getName()); map.put("age", person.getAge()); data.add(map); } SimpleAdapter adapter = new SimpleAdapter(this, data, R.layout.item,// 就是一个界面显示文件item.xml new String[] { "name", "age" },//from： 从结果集中获取数据，将需要显示的数据列名放到该集合 new int[] { R.id.name, R.id.age }// to:将结果集的数据字段对应到listview（item.xml）上 ); listView.setAdapter(adapter); } //第二种： 使用SimpleCursorAdapter作为适配器 private void show2() { Cursor cursor = personService.getCursorScrollData(0, 20); // 使用SimpleCursorAdapter适配器注意两个问题： // 1、返回的游标对象不能被关闭。 // 2、查询语句字段必须有"_id"这个字段，例如：select id as _id,name,age from person。 @SuppressWarnings("deprecation") SimpleCursorAdapter adapter = new SimpleCursorAdapter(this, R.layout.item, cursor, new String[] { "name", "age" }, new int[] { R.id.name, R.id.age }); listView.setAdapter(adapter); } //第三种： 自定义适配器PersonAdapter private void show3() { List<Person> persons = personService.getScrollData(0, 10); PersonAdapter adapter = new PersonAdapter(this, persons, R.layout.item); listView.setAdapter(adapter); } @Override public boolean onCreateOptionsMenu(Menu menu) { getMenuInflater().inflate(R.menu.main, menu); return true; } }
自定义适配器类实现：
package com.example.lservice; import java.util.List; import android.content.Context; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.BaseAdapter; import android.widget.TextView; import com.example.entity.Person; import com.example.listview.R; public class PersonAdapter extends BaseAdapter { //被绑定的数据 private List<Person> persons; //绑定条目界面 private int resource; //布局填充，作用是可以用xml文件生成View对象 private LayoutInflater inflater; public PersonAdapter(Context context,List<Person> persons, int resource) { this.persons = persons; this.resource = resource; inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE); } @Override public int getCount() { return persons.size(); } @Override public Object getItem(int position) { return persons.get(position); } @Override public long getItemId(int position) { return position; } //会缓存之前的View @Override public View getView(int position, View convertView, ViewGroup parent) { TextView nameView =null; TextView ageView = null; if (convertView == null) {// 表示是第一页，需要创建该对象 //生成条目界面对象 convertView = inflater.inflate(resource, null); nameView = (TextView) convertView.findViewById(R.id.name); ageView = (TextView) convertView.findViewById(R.id.age); ViewCache cache = new ViewCache(); cache.ageView=ageView; cache.nameView=nameView; //Tags can also be used to store data within a view without resorting to another data structure. convertView.setTag(cache); }else{ ViewCache cache = (ViewCache) convertView.getTag(); nameView = cache.nameView; ageView = cache.ageView; } // TextView nameView = (TextView) convertView.findViewById(R.id.name); // TextView ageView = (TextView) convertView.findViewById(R.id.age); Person person = persons.get(position); nameView.setText(person.getName()); //setText方法：被设置的值要转换成字符串类型，否则出错 ageView.setText(person.getAge().toString()); return convertView; } /** * 由于每次都要查找View对象，因此就通过setTag将其保存起来。 * @author Administrator * */ private final class ViewCache{ public TextView nameView; public TextView ageView; } }
