完整代码如下：

其中有大部分的代码被注释，那是可以成功运行的。

后来我想啊，游戏有好多种，但是需要统计的内容是一样的。

我就想传参 然后获得返回值的方式 来减少代码量啊。

但是把相关的查询代码放到 带参带返回值的方法中后 就报错了。

期间我debug了一下，发现 db ＝ null 说明db的值没有哦。

所以我估计是db出了问题。

求各位大大看看有啥解决办法吧，谢谢！

package com.example.mscodescanner;

import android.database.Cursor;

import android.database.sqlite.SQLiteDatabase;

import android.os.Bundle;

import android.support.v7.app.AppCompatActivity;

import android.widget.TextView;

import android.widget.Toast;

/**

* Created by jungege on 16/4/21.

*/

public class TicketsRecord extends AppCompatActivity{

//注册控件

private TextView mTv_TotalNum_Online; //中福在线 总张数

private TextView mTv_SurplusNum_Online; //中福在线 剩余张数

private TextView mTv_TotalValue_Online; //中福在线 总钱数

private TextView mTv_SurplusValue_Online; //中福在线 剩余钱数

//注册数据库

private DatabaseContext dbContext;

private SdCardDBHelper dbHelper;

private SQLiteDatabase db;

@Override

protected void onCreate( Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.record_layout);

init(); //初始化

statistical(); //执行统计

}

private void init() {

//实例化控件

mTv_TotalNum_Online = (TextView) findViewById(R.id.tv_TotalNum_Online);

mTv_SurplusNum_Online = (TextView) findViewById(R.id.tv_SurplusNum_Online);

mTv_TotalValue_Online = (TextView) findViewById(R.id.tv_TotalValue_Online);

mTv_SurplusValue_Online = (TextView) findViewById(R.id.tv_SurplusValue_Online);

//实例化数据库

dbContext = new DatabaseContext(TicketsRecord.this);

dbHelper = new SdCardDBHelper(dbContext);

db = dbHelper.getWritableDatabase(); //创建DB对象

}

private void statistical() {

//中福在线

// Cursor cursor_TotalNum = db.rawQuery("select * from Tickets where name = 0", null); //总张数

// Cursor cursor_SurplusNum = db.rawQuery("select * from Tickets where name = 0 and use = 1", null); //剩余张数

// Cursor cursor_TotalValue = db.rawQuery("select sum(price) from Tickets where name = 0", null); //总钱数

// Cursor cursor_SurplusValue = db.rawQuery("select sum(price) from Tickets where name = 0 and use = 1", null); //剩余钱数

//

// if (cursor_TotalNum.moveToFirst() && cursor_SurplusNum.moveToFirst() && cursor_TotalValue.moveToFirst() && cursor_SurplusValue.moveToFirst()){

//

// int count_TotalNum = cursor_TotalNum.getCount();

// int count_SurplusNum = cursor_SurplusNum.getCount();

// int count_TotalValue = cursor_TotalValue.getInt(0);

// int count_SurplusValue = cursor_SurplusValue.getInt(0);

//

// mTv_TotalNum_Online.setText(String.valueOf(count_TotalNum));

// mTv_SurplusNum_Online.setText(String.valueOf(count_TotalNum - count_SurplusNum));

// mTv_TotalValue_Online.setText(String.valueOf(count_TotalValue));

// mTv_SurplusValue_Online.setText(String.valueOf(count_TotalValue - count_SurplusValue));

//

// } else {

// mTv_TotalNum_Online.setText("没有记录");

// }

// //关闭游标

// cursor_TotalNum.close();

// cursor_SurplusNum.close();

// cursor_TotalValue.close();

// cursor_SurplusValue.close();

TicketsRecord hello = new TicketsRecord();

int wellcome = hello.statManage(0);

mTv_TotalNum_Online.setText(String.valueOf(wellcome));

}

//Statistical management

private int statManage(int name){

//Cursor cursor_TotalNum = db.rawQuery("select sum(price) from Tickets where name = ？", new String[]{String.valueOf(name)});

Cursor cursor_TotalNum = db.rawQuery("select sum(price) from Tickets where name = " + name, null); //总张数

cursor_TotalNum.moveToFirst();

int count_TotalNum = cursor_TotalNum.getColumnIndex("sum(price)");

cursor_TotalNum.close();

return count_TotalNum;

//return "欢迎您" + name + "!";

}

}