如题,本文将介绍 listview的点击事件,simpleAdapter和arrayadapter的原理和使用.
1.ListView的注册点击事件
//注册点击事件
personListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
/**
*
* @param parent 当前ListView
* @param view 代表当前被点击的条目
* @param position 当前条目的位置
* @param id 当前被点击的条目的id
*/
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
Log.d(tag,"点击了!");
/*
方法 1:
*/
TextView tv_name = (TextView) view.findViewById(R.id.tv_name);
Toast.makeText(MyActivity.this,"姓名是1:"+tv_name.getText(),Toast.LENGTH_SHORT).show();
/*
方法 2:
*/
String name = persons.get(position).getName();
Toast.makeText(MyActivity.this,"姓名是2:"+name,Toast.LENGTH_SHORT).show();
/*
方法 3:
*/
Person p=(Person)parent.getItemAtPosition(position);
Toast.makeText(MyActivity.this,"姓名是3:"+p.getName(),Toast.LENGTH_SHORT).show(); }
});
注:注册一个onItemClick事件,方法1:利用当前被点击条目的视图根据id找到tv_name,然后使用吐司显示被点击的内容.
方法2:利用当前被点击条目的位置,然后根据位置取到姓名;
方法3:parent在这里表示ListView的位置,这里得到被点击条目的位置,取到person对象并显示.
com/amos/android_db/MyActivity.java
package com.amos.android_db; import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.*;
import com.amos.android_db.dao.Person;
import com.amos.android_db.dao.PersonDao; import java.util.List; public class MyActivity extends Activity { private ListView personListView;
private List<Person> persons;
LayoutInflater inflater;//打气筒
String tag="MyActivity.class"; @Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//inflater是一个系统服务,初始化系统服务,利用inflater将一个布局文件转化为一个对象
inflater = (LayoutInflater) this.getSystemService(LAYOUT_INFLATER_SERVICE); setContentView(R.layout.main);
PersonDao personDao = new PersonDao(this);
persons = personDao.findAll(); //第一步,得到组件的id的引用
personListView = (ListView) this.findViewById(R.id.listview_show_data);
//第二步,设置组件要显示的内容,listview要显示的内容比较复杂,需要数据的适配器
personListView.setAdapter(new MyListAdapter()); //注册点击事件
personListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
/**
*
* @param parent 当前ListView
* @param view 代表当前被点击的条目
* @param position 当前条目的位置
* @param id 当前被点击的条目的id
*/
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
Log.d(tag,"点击了!");
/*
方法 1:
*/
TextView tv_name = (TextView) view.findViewById(R.id.tv_name);
Toast.makeText(MyActivity.this,"姓名是1:"+tv_name.getText(),Toast.LENGTH_SHORT).show();
/*
方法 2:
*/
String name = persons.get(position).getName();
Toast.makeText(MyActivity.this,"姓名是2:"+name,Toast.LENGTH_SHORT).show();
/*
方法 3:
*/
Person p=(Person)parent.getItemAtPosition(position);
Toast.makeText(MyActivity.this,"姓名是3:"+p.getName(),Toast.LENGTH_SHORT).show(); }
}); } public class MyListAdapter extends BaseAdapter { /**
* 返回当前有多少个条目
* @return
*/ @Override
public int getCount() {
return persons.size();
} /**
* 返回当前position位置对应的条目的object对象
* @param position
* @return
*/
@Override
public Object getItem(int position) {
return persons.get(position);
} /**
* 返回当前position位置对应条目的id
* @param position
* @return
*/
@Override
public long getItemId(int position) {
return position;
} /**
* 返回一个条目显示的具体内容
* 计算当前界面 会有多少个条目出现
* 1.得到每一个textview的高度
* 2.得到listview的高度
* 3.listview高度/textview高度=得到了一个屏幕显示textview的的个数
* listview的每一个条目的显示都需要调用一次getView的方法
* 屏幕上有多个item显示就会调用多少getview的方法
*
* @param position
* @param convertView
* @param parent
* @return
*/ @Override
public View getView(int position, View convertView, ViewGroup parent) {
// TextView textView = new TextView(MyActivity.this);
// textView.setText(persons.get(position).getName()+":"+persons.get(position).getAge());
// return textView; View view = inflater.inflate(R.layout.item, null);
Person person = persons.get(position);
TextView tv_name = (TextView) view.findViewById(R.id.tv_name);
TextView tv_age = (TextView) view.findViewById(R.id.tv_age);
tv_name.setText("姓名:" + person.getName());
tv_age.setText("年龄:" + person.getAge());
Log.d("item:",""+position);
return view;
}
} }
2.simpleAdapter的使用
//第二步,设置组件要显示的内容,listview要显示的内容比较复杂,需要数据的适配器
// personListView.setAdapter(new MyListAdapter());//自实现BaseAdapter
List<Map<String, String>> data = new ArrayList<Map<String, String>>();
for (Person p : persons) {
Map<String, String> datavalue = new HashMap<String, String>();
datavalue.put("name", p.getName());
datavalue.put("age", p.getAge().toString());
data.add(datavalue);
}
personListView.setAdapter(new SimpleAdapter(this, data, R.layout.item, new String[]{"name", "age"}, new int[]{R.id.tv_name, R.id.tv_age}));
之前的适配器是继承BaseAdapter,实现了getCount(),getItem(int position),getItemId(int position),getView(int position, View convertView, ViewGroup parent)方法,这里调用SimpleAdapter方法,查看SimpleAdapter的实现也可以发现其也是继承了BaseAdapter类.
SimpleAdapter(android.content.Context context, java.util.List<? extends java.util.Map<java.lang.String, ?>> data, int resource, java.lang.String[] from, int[] to) { throw new RuntimeException("Stub!"); }
context表示上下文,data表示要显示的内容,resource表示资源文件的id,from这里表示的是map里的key,然后其id依次相对应为tv_name,和tv_age.
3.ArrayAdapter的使用
//3)arrayAdapter
// public ArrayAdapter(android.content.Context context, int resource, int textViewResourceId, T[] objects) { throw new RuntimeException("Stub!"); } String[] personArray = new String[persons.size()];
for(int i=0;i<persons.size();i++){
personArray[i] = persons.get(i).getName();
}
personListView.setAdapter(new ArrayAdapter(this,R.layout.item,R.id.tv_name,personArray));
这里显示的只是一侧的内容,R.id.tv_name,这里只显示姓名,ArrayAdapter适合只有一列内容的数据显示.
4.SimpleCursoAdapter的使用
//4)simpleCursorAdapter
//要求数据的组件名称以下划线
Cursor cursor = personDao.findAllByCursor() ;
personListView.setAdapter(new SimpleCursorAdapter(this,R.layout.item,cursor,new String[]{"name","age"},new int[]{R.id.tv_name,R.id.tv_age}));
PersonDao.java中增加一个方法用来返回cursor结果集.
public Cursor findAllByCursor(){
SQLiteDatabase db = dbHelper.getReadableDatabase();
Cursor cursor=null;
if (db.isOpen()) {
cursor = db.query("person", null, null, null, null, null, null);
}
运行时出现的问题:
06-16 18:11:25.106 485-485/com.amos.android_db E/AndroidRuntime﹕ FATAL EXCEPTION: main
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.amos.android_db/com.amos.android_db.MyActivity}: java.lang.IllegalArgumentException: column '_id' does not exist
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
at android.app.ActivityThread.access$1500(ActivityThread.java:117)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:123)
at android.app.ActivityThread.main(ActivityThread.java:3683)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:507)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.IllegalArgumentException: column '_id' does not exist
at android.database.AbstractCursor.getColumnIndexOrThrow(AbstractCursor.java:314)
at android.widget.CursorAdapter.init(CursorAdapter.java:111)
at android.widget.CursorAdapter.<init>(CursorAdapter.java:90)
at android.widget.ResourceCursorAdapter.<init>(ResourceCursorAdapter.java:47)
at android.widget.SimpleCursorAdapter.<init>(SimpleCursorAdapter.java:84)
at com.amos.android_db.MyActivity.onCreate(MyActivity.java:69)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
at android.app.ActivityThread.access$1500(ActivityThread.java:117)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:123)
at android.app.ActivityThread.main(ActivityThread.java:3683)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:507)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
at dalvik.system.NativeStart.main(Native Method)
这里是要求返回来的结果集中主键必须为_id,这里我们设置的是personid,这里要么改写数据库结构,要么改写查询sql的语句.
如下所示:
cursor= db.rawQuery("select personid as _id,name,age from person",null);
本文源码:https://github.com/amosli/android_basic/tree/android_db