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
