数据库事务

Posted 2020-07-21 beens

layout代码：

<?xml version="1.0" encoding="utf-8"?>
<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:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:orientation="vertical"
    tools:context="com.example.my.testapp.TestActivity">
    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="初始化数据库"
        android:onClick="bt_onClick"/>
    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="升级数据库"
        android:onClick="bt1_onClick"/>
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
        <EditText
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:id="@+id/et_id"
            android:hint="id"/>

        <EditText
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:id="@+id/et_name"
            android:hint="name"/>

    </LinearLayout>
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
        <EditText
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:id="@+id/et_sex"
            android:hint="sex"/>
        <EditText
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:id="@+id/et_age"
            android:hint="age"/>
    </LinearLayout>
    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="新增数据"
        android:onClick="bt2_onClick"/>
    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="查询数据"
        android:onClick="bt3_onClick"/>

    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="带条件查询数据"
        android:onClick="bt4_onClick"/>
    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="修改数据"
        android:onClick="bt5_onClick"/>
    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="删除数据"
        android:onClick="bt6_onClick"/>
    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="数据库事务"
        android:onClick="bt7_onClick"/>
</LinearLayout>

Activity代码：

package com.example.my.testapp;

import android.content.ContentValues;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.EditText;
import android.widget.Toast;

public class TestActivity extends AppCompatActivity {

    EditText et_id,et_name,et_sex,et_age;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_test);

        et_id=(EditText)findViewById(R.id.et_id);
        et_name=(EditText)findViewById(R.id.et_name);
        et_sex=(EditText)findViewById(R.id.et_sex);
        et_age=(EditText)findViewById(R.id.et_age);
    }
    //初始化数据库
    public void bt_onClick(View v)
    {
        //使用工具类得到数据库对象
        MyDBHelper myDBHelper=new MyDBHelper("test.db",1);

        //得到连接
        SQLiteDatabase sqLiteDatabase=myDBHelper.getWritableDatabase();

        Toast.makeText(TestActivity.this, "连接数据库成功", Toast.LENGTH_SHORT).show();
        //关闭连接
        sqLiteDatabase.close();
    }

    public void bt1_onClick(View v)
    {
        //使用工具类得到数据库对象
        MyDBHelper myDBHelper=new MyDBHelper("test.db",2);

        //得到连接
        SQLiteDatabase sqLiteDatabase=myDBHelper.getWritableDatabase();

        Toast.makeText(TestActivity.this, "连接数据库成功", Toast.LENGTH_SHORT).show();
        //关闭连接
        sqLiteDatabase.close();
    }

    //插入新数据
    public void bt2_onClick(View v)
    {
        //1.连接数据库，得到数据库连接对象

        //得到连接
        SQLiteDatabase sqLiteDatabase=new MyDBHelper("test.db",2).getWritableDatabase();

        //2.准备数据
        ContentValues cv=new ContentValues();
        cv.put("name",et_name.getText().toString());
        cv.put("sex",et_sex.getText().toString());
        cv.put("age",et_age.getText().toString());

        //3.调用插入数据
        long l=sqLiteDatabase.insert("t_user", null, cv);

        Toast.makeText(TestActivity.this, "插入的数据主键="+l, Toast.LENGTH_SHORT).show();

        //4.关闭连接
        sqLiteDatabase.close();
    }

    //数据查询
    public void bt3_onClick(View v)
    {
        //1.连接数据库，得到数据库连接对象

        //得到连接
        SQLiteDatabase sqLiteDatabase=new MyDBHelper("test.db",2).getWritableDatabase();

        //2.全表全字段查询
        Cursor c=sqLiteDatabase.query("t_user", null, null, null, null, null, null);

        //3.遍历结果集
        while (c.moveToNext())
        {
            //读取数据
            String str=c.getLong(c.getColumnIndex("_id"))+" name = "+c.getString(1)+" sex = "+c.getString(2)
                    +" age= "+c.getString(c.getColumnIndex("age"));

            Log.e("TAG",str);
        }
        Toast.makeText(TestActivity.this, "结果集的条数"+c.getCount(), Toast.LENGTH_SHORT).show();


        c.close();

        //4.关闭连接
        sqLiteDatabase.close();

    }

    public void bt4_onClick(View v)
    {
        //1.连接数据库，得到数据库连接对象

        //得到连接
        SQLiteDatabase sqLiteDatabase=new MyDBHelper("test.db",2).getWritableDatabase();

        String strwhere="1=1";

        //select * from t_user where 1=1 and _id =1 and name like ‘%张%‘
        //得到条件
        if (et_id.getText().length()>0)
        {
            strwhere += " and _id= "+et_id.getText().toString();
        }

        if (et_name.getText().length()>0)
        {
            strwhere += " and name like ‘%"+et_name.getText().toString()+"%‘";
        }

        if (et_sex.getText().length()>0)
        {
            strwhere += " and sex = ‘"+et_id.getText().toString()+"‘";
        }

        if (et_age.getText().length()>0)
        {
            strwhere += " and age = "+et_id.getText().toString();
        }
        //2.全表全字段查询
        Cursor c=sqLiteDatabase.query("t_user", null, strwhere, null, null, null, null);

        //3.遍历结果集
        while (c.moveToNext())
        {
            //读取数据
            String str=c.getLong(c.getColumnIndex("_id"))+" name = "+c.getString(1)+" sex = "+c.getString(2)
                    +" age= "+c.getString(c.getColumnIndex("age"));

            Log.e("TAG",str);
        }
        Toast.makeText(TestActivity.this, "结果集的条数"+c.getCount(), Toast.LENGTH_SHORT).show();


        c.close();

        //4.关闭连接
        sqLiteDatabase.close();
    }

    public void bt5_onClick(View v)
    {
        //1.连接数据库，得到数据库连接对象

        //得到连接
        SQLiteDatabase sqLiteDatabase=new MyDBHelper("test.db",2).getWritableDatabase();

        //2.修改
        ContentValues cv=new ContentValues();
        cv.put("name",et_name.getText().toString());
        cv.put("name",et_sex.getText().toString());
        cv.put("name", et_age.getText().toString());

        int i=sqLiteDatabase.update("t_user", cv, "_id=?", new String[]{et_id.getText().toString()});

        Toast.makeText(TestActivity.this, "修改的记录条数"+i, Toast.LENGTH_SHORT).show();

        //4.关闭连接
        sqLiteDatabase.close();

    }

    public void bt6_onClick(View v)
    {
        //1.连接数据库，得到数据库连接对象

        //得到连接
        SQLiteDatabase sqLiteDatabase=new MyDBHelper("test.db",2).getWritableDatabase();

        //2.删除
        int i=sqLiteDatabase.delete("t_user", "_id=?", new String[]{et_id.getText().toString()});

        Toast.makeText(TestActivity.this, "修改的记录条数"+i, Toast.LENGTH_SHORT).show();

        //4.关闭连接
        sqLiteDatabase.close();

    }

    public void bt7_onClick(View v)
    {
        //1.连接数据库，得到数据库连接对象

        SQLiteDatabase sqLiteDatabase = new MyDBHelper("test.db", 2).getWritableDatabase();
        try {
            //得到连接


            //启动事务
            sqLiteDatabase.beginTransaction();

            //2.修改
            ContentValues cv = new ContentValues();
            cv.put("age", "43");


            //修改1
            int i = sqLiteDatabase.update("t_user", cv, "_id=1", null);

            //抛出异常
//            if (i > 0) {
//                throw new RuntimeException("模拟事务异常");
//            }

            ContentValues cv2 = new ContentValues();
            cv2.put("age", "53");

            //修改2
            int k = sqLiteDatabase.update("t_user", cv2, "_id=2", null);

            //设置事务是成功完成的
            sqLiteDatabase.setTransactionSuccessful();



            Toast.makeText(TestActivity.this, "修改的记录条数" + (i + k), Toast.LENGTH_SHORT).show();


        }
        catch (Exception e)
        {
            e.printStackTrace();

            Toast.makeText(TestActivity.this, "修改出错", Toast.LENGTH_SHORT).show();
        }
        finally {
            //一定会被执行代码
            //结束事务
            //1.没有异常，提交事务
            //2.发生异常，回滚事务
            sqLiteDatabase.endTransaction();

            //4.关闭连接
            sqLiteDatabase.close();
        }

    }
    //实现SQLiteOpenHelper内部类
    class  MyDBHelper extends SQLiteOpenHelper
    {
        //构造方法
        public MyDBHelper(String dbname,int ver)
        {
            //显示调用父类的构造方法
            //必须在第一行
            super(TestActivity.this,dbname,null,ver);
        }
        //初始化数据库
        @Override
        public void onCreate(SQLiteDatabase db) {

            //1.执行创建数据库的语句
            String sql = "CREATE TABLE \"main\".\"t_user\" " +
                    "(\"_id\"  INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL," +
                    "\"name\"  VARCHAR(20),\"sex\"  CHAR(1)," +
                    "\"age\"  INTEGER)";
            db.execSQL(sql);

            Log.e("TAG","表创建成功");

            //2.初始化数据的语句 insert语句
            sql="";

            ContentValues contentValues = new ContentValues();

            contentValues.put("name","张全蛋");
            contentValues.put("sex","男");
            contentValues.put("age","20");

            //执行插入，返回主键
            long l=db.insert("t_user",null,contentValues);

            Log.e("TAG","初始化数据 = "+1);
        }


        //升级数据库
        //触发条件：当版本号变大
        @Override
        public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

            //修改数据
            if (newVersion ==2)
            {
                //调用db的更新方法
                ContentValues cv=new ContentValues();
                cv.put("name", "李狗蛋");

                String sql="update t_user set name=‘李狗蛋‘ where _id=1";

                String[] str={"1","18"};
                int i=db.update("t_user",cv,"_id=? and age > ?",str);

                Log.e("TAG","升级数据 数据条数="+i);
            }

        }
    }
}