Android心得4.5--SQLite数据库--事务处理、ListView列表显示

1. 使用SQLiteDatabase的beginTransaction()方法可以开启一个事务，程序执行到endTransaction() 方法时会检查事务的标志是否为成功，如果程序执行到endTransaction()之前调用了setTransactionSuccessful()
方法设置事务的标志为成功则提交事务，如果没有调用setTransactionSuccessful() 方法则回滚事务。使用例子如下：

SQLiteDatabase db = ....;

db.beginTransaction();//开始事务

try {

db.execSQL("insert into person(name, age) values(?,?)", new Object[]{"传智播客", 4});

db.execSQL("update person set name=? where personid=?", new Object[]{"传智", 1});

db.setTransactionSuccessful();//调用此方法会在执行到endTransaction() 时提交当前事务，如果不调用此方法会回滚事务

} finally {

db.endTransaction();//由事务的标志决定是提交事务，还是回滚事务

}

db.close();

上面两条SQL语句在同一个事务中执行。

2.ListView列表显示

先在Layout文件夹下创建一个item.xml文件，水平线性布局显示文件，然后在main.xml文件下引用<ListView/>.

网格显示跟列表显示基本上一样。

有三种方法可以完成操作，分别是下面代码的show()、show2()、show3()，show3()是自定义的适配器，某些特殊情况下会用到。

代码如下：

package cn.itcast.db;

import java.util.ArrayList;

import java.util.HashMap;

import java.util.List;

import cn.itcast.adapter.PersonAdapter;

import cn.itcast.domain.Person;

import cn.itcast.service.PersonService;

import android.app.Activity;

import android.database.Cursor;

import android.os.Bundle;

import android.view.View;

import android.widget.AdapterView;

import android.widget.AdapterView.OnItemClickListener;

import android.widget.ListView;

import android.widget.SimpleAdapter;

import android.widget.SimpleCursorAdapter;

import android.widget.Toast;

public class MainActivity extends Activity {


private ListView listView;


private PersonService personService;


@Override


public void onCreate(Bundle savedInstanceState) {


super.onCreate(savedInstanceState);


setContentView(R.layout.main);


personService = new PersonService(this);


listView = (ListView) this.findViewById(R.id.listView);


listView.setOnItemClickListener(new ItemClickListener());


show2();


}


private final class ItemClickListener implements OnItemClickListener{


public void onItemClick(AdapterView<?> parent, View view, int position, long id) {


ListView lView = (ListView)parent;


/* 自定义适配器


Person person = (Person) lView.getItemAtPosition(position);


Toast.makeText(getApplicationContext(), person.getId().toString(), 1).show();*/


Cursor cursor = (Cursor) lView.getItemAtPosition(position);


int personid = cursor.getInt(cursor.getColumnIndex("_id"));


Toast.makeText(getApplicationContext(), personid+ "", 1).show();


}


}


//自定义适配器


private void show3() {


List<Person> persons = personService.getScrollData(0, 20);


PersonAdapter adapter = new PersonAdapter(this, persons, R.layout.item);


listView.setAdapter(adapter);


}


private void show2() {


Cursor cursor = personService.getCursorScrollData(0, 20);


SimpleCursorAdapter adapter = new SimpleCursorAdapter(this, R.layout.item, cursor,


new String[]{"name", "phone", "amount"}, new int[]{R.id.name, R.id.phone, R.id.amount});


listView.setAdapter(adapter);


}


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> item = new HashMap<String, Object>();


item.put("name", person.getName());


item.put("phone", person.getPhone());


item.put("amount", person.getAmount());


item.put("id", person.getId());


data.add(item);


}


SimpleAdapter adapter = new SimpleAdapter(this, data, R.layout.item,


new String[]{"name", "phone", "amount"}, new int[]{R.id.name, R.id.phone, R.id.amount});


listView.setAdapter(adapter);


}

}

Adapter代码：

package cn.itcast.adapter;

import java.util.List;

import cn.itcast.db.R;

import cn.itcast.domain.Person;

import android.content.Context;

import android.view.LayoutInflater;

import android.view.View;

import android.view.ViewGroup;

import android.widget.BaseAdapter;

import android.widget.TextView;

public class PersonAdapter extends BaseAdapter {


private List<Person> persons;//在绑定的数据


private int resource;//绑定的条目界面


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();//数据总数


}


@Override


public Object getItem(int position) {


return persons.get(position);


}


@Override


public long getItemId(int position) {


return position;


}


@Override


public View getView(int position, View convertView, ViewGroup parent) {


TextView nameView = null;


TextView phoneView = null;


TextView amountView = null;


if(convertView==null){


convertView = inflater.inflate(resource, null);//生成条目界面对象


nameView = (TextView) convertView.findViewById(R.id.name);


phoneView = (TextView) convertView.findViewById(R.id.phone);


amountView = (TextView) convertView.findViewById(R.id.amount);


ViewCache cache = new ViewCache();


cache.nameView = nameView;


cache.phoneView = phoneView;


cache.amountView = amountView;


convertView.setTag(cache);


}else{


ViewCache cache = (ViewCache) convertView.getTag();


nameView = cache.nameView;


phoneView = cache.phoneView;


amountView = cache.amountView;


}


Person person = persons.get(position);


//下面代码实现数据绑定


nameView.setText(person.getName());


phoneView.setText(person.getPhone());


amountView.setText(person.getAmount().toString());


return convertView;


}


private final class ViewCache{


public TextView nameView;


public TextView phoneView;


public TextView amountView;


}

}