Android心得4.5--SQLite數據庫--事務處理、ListView列表顯示

1.   使用SQLiteDatabase的beginTransaction()方法可以開啟一個事務，程序執行到endTransaction() 方法時會檢查事務的標志是否為成功，如果程序執行到endTransaction()之前調用了setTransactionSuccessful() 方法設置事務的標志為成功則提交事務，如果沒有調用setTransactionSuccessful() 方法則回滾事務。使用例子如下：
 SQLiteDatabase db = ....;

db.beginTransaction();//開始事務

try {

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

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

    db.setTransactionSuccessful();//調用此方法會在執行到endTransaction() 時提交當前事務，如果不調用此方法會回滾事務

} finally {

    db.endTransaction();//由事務的標志決定是提交事務，還是回滾事務

}

db.close();

上面兩條SQL語句在同一個事務中執行。

2.ListView列表顯示

   先在Layout文件夾下創建一個item.xml文件，水平線性布局顯示文件，然後在main.xml文件下引用<ListView/>.

   網格顯示跟列表顯示基本上一樣。

   有三種方法可以完成操作，分別是下面代碼的show()、show2()、show3()，show3()是自定義的適配器，某些特殊情況下會用到。

代碼如下：

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;

                     /* 自定義適配器

                     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();

              }

    }

  

  

    //自定義適配器

       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代碼：

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;//在綁定的數據

       private int resource;//綁定的條目界面

       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();//數據總數

       }

 

       @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);//生成條目界面對象

                     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);

              //下面代碼實現數據綁定

              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;

       }

 

}