android:sqlite 資料庫的事務詳解
阿新 • • 發佈:2018-12-31
sqlite 資料庫的事務詳解,所有的解釋都在程式碼中進行了註釋
關於事務的應用主要都在MainActivity的onClickTransferAccountsSuccess和onClickTransferAccountsError方法中做的註釋,請執行體會
執行結果如下圖
1.佈局檔案activity_main.xml
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" tools:context=".MainActivity" > <Button android:id="@+id/btn_success" android:onClick="onClickTransferAccountsSuccess" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="正確轉賬(正確的事物)" /> <Button android:id="@+id/btn_error" android:onClick="onClickTransferAccountsError" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="錯誤轉賬(異常的事物)" /> <ListView android:id="@+id/lv_many" android:layout_width="match_parent" android:layout_height="match_parent" ></ListView> </LinearLayout>
2.ListView的item佈局檔案item_money.xml
<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="horizontal" > <TextView android:id="@+id/tv_id" android:layout_width="40dp" android:layout_height="wrap_content" /> <TextView android:id="@+id/tv_name" android:layout_width="60dp" android:layout_height="wrap_content"/> <TextView android:id="@+id/tv_money" android:layout_width="60dp" android:layout_height="wrap_content"/> <TextView android:id="@+id/tv_phone" android:layout_width="100dp" android:layout_height="wrap_content"/> <TextView android:id="@+id/tv_age" android:layout_width="50dp" android:layout_height="wrap_content"/> </LinearLayout>
3.activity的實現類MainActivity.java
package com.smartdot.transaction; import java.util.ArrayList; import java.util.HashMap; import java.util.List; import java.util.Map; import android.app.Activity; import android.content.ContentValues; import android.database.Cursor; import android.database.sqlite.SQLiteDatabase; import android.os.Bundle; import android.util.Log; import android.view.View; import android.view.ViewGroup; import android.widget.BaseAdapter; import android.widget.ListView; import android.widget.TextView; import android.widget.Toast; public class MainActivity extends Activity { private static final String TAG = "MainActivity"; private OpenHelper helper; private ListView lv_many; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); helper = new OpenHelper(this); lv_many = (ListView) findViewById(R.id.lv_many); setBaseAdapter();//讀取資料庫的資料,並設定lv_many列表的資料 } /** * 正確的轉賬方法 */ public void onClickTransferAccountsSuccess(View v) { SQLiteDatabase db = helper.getWritableDatabase(); db.beginTransaction();//開啟事務 try { //馬漢缺錢要王超給他轉賬100元 db.execSQL("update user set money=money-100 where name=? and money>=100",new String[]{"王朝"}); db.execSQL("update user set money=money+100 where name=? and (select money from user u where u.name=?)>=100",new String[]{"馬漢","王朝"}); db.setTransactionSuccessful();//事務正確結束,如果此方法不執行,則所有的資料增刪改操作都會回滾 Toast.makeText(MainActivity.this, "轉賬成功!", Toast.LENGTH_SHORT).show(); Log.i(TAG, "轉賬成功!"); } catch (Exception e){ Toast.makeText(MainActivity.this, "伺服器忙,請稍後!", Toast.LENGTH_SHORT).show(); Log.e(TAG, "伺服器忙,請稍後!"); } finally { db.endTransaction();//關閉事務 setBaseAdapter(); } } /** * 錯誤的轉賬方法 */ public void onClickTransferAccountsError(View v) { SQLiteDatabase db = helper.getWritableDatabase(); db.beginTransaction();//開啟事務 try { //馬漢缺錢要給他王超轉賬100元 db.execSQL("update user set money=money-100 where name=?",new String[]{"王朝"}); int i = 10/0;//故意設定一個異常 db.execSQL("update user set money=money+100 where name=?",new String[]{"馬漢"}); db.setTransactionSuccessful();//事務正確結束,如果此方法不執行,則所有的資料增刪改操作都會回滾 Toast.makeText(MainActivity.this, "轉賬成功!", Toast.LENGTH_SHORT).show();//此處永遠不會執行 } catch (Exception e){ Toast.makeText(MainActivity.this, "伺服器忙,請稍後!", Toast.LENGTH_SHORT).show(); Log.e(TAG, "伺服器忙,請稍後!");//真正企業開發,一般會報伺服器忙,請稍後。不會丟擲異常給使用者!!! } finally { db.endTransaction();//關閉事務 setBaseAdapter(); } } /** * 重新設定列表的介面卡 */ public void setBaseAdapter() { List<Map<String,String>> list = query();//轉完賬查詢記錄 MyBaseAdapter mBaseAdapter = new MyBaseAdapter(list);//設定listView的介面卡 lv_many.setAdapter(mBaseAdapter); } /** * 查詢記錄 * @return */ public List<Map<String,String>> query() { SQLiteDatabase db = helper.getWritableDatabase(); Cursor cursor = db.query("user", new String[]{"name","money","age","phone","_id"}, null, null, null, null, null); List<Map<String,String>> list = new ArrayList<Map<String,String>>(); Map<String,String> map; while(cursor.moveToNext()) { map = new HashMap<String, String>(); map.put("name", cursor.getString(0)); map.put("money", cursor.getString(1)); map.put("age", cursor.getInt(2) + ""); map.put("phone", cursor.getString(3)); map.put("id", cursor.getInt(4) + ""); list.add(map); } return list; } class MyBaseAdapter extends BaseAdapter { public List<Map<String,String>> list ; public MyBaseAdapter() { } public MyBaseAdapter(List<Map<String,String>> list) { this.list = list; } @Override public int getCount() { return list == null?0:list.size(); } @Override public Object getItem(int position) { // TODO Auto-generated method stub return list == null?null:list.get(position); } @Override public long getItemId(int position) { // TODO Auto-generated method stub return position; } /** * 通過介面卡把數值填充到ListView中 */ @Override public View getView(int position, View convertView, ViewGroup parent) { ConvertViewTag tag ;//用於快取內部的find的物件 TextView tv_id = null; TextView tv_name = null; TextView tv_age = null; TextView tv_phone = null; TextView tv_money = null; if(convertView == null) { convertView = View.inflate(MainActivity.this, R.layout.item_money,null); tv_id = (TextView) convertView.findViewById(R.id.tv_id); tv_name = (TextView) convertView.findViewById(R.id.tv_name); tv_money = (TextView) convertView.findViewById(R.id.tv_money); tv_age = (TextView) convertView.findViewById(R.id.tv_age); tv_phone = (TextView) convertView.findViewById(R.id.tv_phone); tag = new ConvertViewTag(); tag.tv_id = tv_id; tag.tv_money = tv_money; tag.tv_age = tv_age; tag.tv_name = tv_name; tag.tv_phone = tv_phone; convertView.setTag(tag);//快取獲得的View物件,如果資料多的時候避免二次建立 } else { tag = (ConvertViewTag) convertView.getTag();//獲取快取的物件 tv_id = tag.tv_id; tv_name = tag.tv_name; tv_money = tag.tv_money; tv_age = tag.tv_age; tv_phone = tag.tv_phone; } Map<String, String> map = list.get(position); tv_id.setText(map.get("id")); tv_name.setText(map.get("name")); tv_money.setText(map.get("money")); tv_age.setText(map.get("age")); tv_phone.setText(map.get("phone")); return convertView; } class ConvertViewTag { public TextView tv_id; public TextView tv_name; public TextView tv_money; public TextView tv_age; public TextView tv_phone; } } }
4.SQLiteOpenHelper的實現類OpenHelper.java
package com.smartdot.transaction;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
/**
* 實現android提供的抽象類SQLiteOpenHelper,用於sqlite資料庫的操作
*
* @author wangguang
*
*/
public class OpenHelper extends SQLiteOpenHelper {
/**
* 第一次呼叫資料庫,對出具庫進行訪問。
*
* @param context
*/
public OpenHelper(Context context) {
// 資料版本version只能比之前高,不得低於之前設定的版本號
super(context, "transaction.db", null, 1);// 系統建立資料庫
}
/**
* 當資料庫(表)發生改變時可呼叫此方法
*
* @param Context
* context 上下文
* @param int version 資料庫版本
*/
public OpenHelper(Context context, int version) {
// 資料版本version只能比之前高,不得低於之前設定的版本號
super(context, "smartdot.db", null, version);
}
/**
* 當資料庫第一次建立的時候建立<br>
* 這個表特別適合做建立表的操作
*/
@Override
public void onCreate(SQLiteDatabase db) {
String creatTable = "create table user (_id integer PRIMARY KEY AUTOINCREMENT NOT NULL,name varchar,money varchar(20),phone varchar,age int,sex int)";
db.execSQL(creatTable);
db.execSQL(
"INSERT INTO USER (NAME,money,PHONE,SEX,AGE) VALUES(?,?,?,?,?)",
new Object[] { "王朝", "100000", "18701545309", 1, 30 });// 新增測試資料
db.execSQL(
"INSERT INTO USER (NAME,money,PHONE,SEX,AGE) VALUES(?,?,?,?,?)",
new Object[] { "馬漢", "1000", "18701545309", 1, 30 });// 新增測試資料
}
/**
* 當資料庫版本發生改變的時候呼叫此方法,此方法適合修改資料庫的處理修改表,新增表,刪除表<br>
*
* @param SQLiteDatabase
* db<br>
* @param int oldVersion 老版本號<br>
* @param int newVersion 新版本號<br>
*/
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
}