Android心得4.5--SQLite数据库--事务处理

wuliws

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;
       }
 
}
 
转载自：http://leili.iyunv.com/blog/1636534