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 + "!";
}
}
你确定你这样的写法可以吗?你试一下这样写?:
Cursor cursor_TotalNum = db.rawQuery("select sum(price) from Tickets where name = ?", new String[]{name});
具体是什么错误,贴出来看看啊
你不需要new TicketsRecord();直接调用statManage(0);即可
根据 idisfkj 提供的答案,程序成功运行,非常感谢。同时在这里贴上修改后的代码。供遇到同样问题的同学参考。
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;
import java.util.Arrays;
/**
* 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
int[] online_result = statManage(0);
mTv_TotalNum_Online.setText(String.valueOf(online_result[0]));
mTv_SurplusNum_Online.setText(String.valueOf(online_result[1]));
mTv_TotalValue_Online.setText(String.valueOf(online_result[2]));
mTv_SurplusValue_Online.setText(String.valueOf(online_result[3]));
}
//Statistical management
private int[] statManage(int name){
int[] tempScores = new int[4];
Cursor cursor_TotalNum = db.rawQuery("select * from Tickets where name = " + name, null); //总张数
Cursor cursor_SurplusNum = db.rawQuery("select * from Tickets where name = ? and use = 1", new String[]{String.valueOf(name)}); //剩余张数
Cursor cursor_TotalValue = db.rawQuery("select sum(price) from Tickets where name = " + name, null); //总钱数
Cursor cursor_SurplusValue = db.rawQuery("select sum(price) from Tickets where name = ? and use = 1", new String[]{String.valueOf(name)}); //剩余钱数
cursor_TotalNum.moveToNext();
cursor_SurplusNum.moveToNext();
cursor_TotalValue.moveToNext();
cursor_SurplusValue.moveToNext();
tempScores[0] = cursor_TotalNum.getCount(); //总张数
tempScores[1] = cursor_SurplusNum.getCount(); //已用张数
tempScores[1] = tempScores[0] - tempScores[1]; //总张数 - 已用 = 剩余张数
tempScores[2] = cursor_TotalValue.getInt(cursor_TotalValue.getColumnIndex("sum(price)")); //总钱数
tempScores[3] = cursor_SurplusValue.getInt(cursor_SurplusValue.getColumnIndex("sum(price)")); //已用钱数
tempScores[3] = tempScores[2] - tempScores[3]; //总钱数 - 已用 = 剩余钱数
cursor_TotalNum.close();
cursor_SurplusNum.close();
cursor_TotalValue.close();
cursor_SurplusValue.close();
return tempScores;
}
}