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;
      
}
 
}