Android心得4.5--SQLite数据库--事务处理
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.iteye.com/blog/1636534
