                        课程
                    
                        /移动开发
                        
                            /Android
                        
                        /Android攻城狮的第二门课（第3季）

为什么主键没有自增长？

代码跟老师的一样啊，为什么主键没有自增长？都是NULL

SQLiteDatabase db = openOrCreateDatabase("user.db",MODE_PRIVATE,null);
db.execSQL("create table if not exists usertb (_id integer not null primary key autoincrement,name text not null,age integer,sex text not null)");
db.execSQL("insert into usertb(name,age,sex) values('张三',18,'女')");
db.execSQL("insert into usertb(name,age,sex) values('李四',19,'女')");
db.execSQL("insert into usertb(name,age,sex) values('王五',20,'男')");
Cursor c = db.rawQuery("select * from usertb",null);
if(c!=null){
    while(c.moveToNext()){
        Log.i("info","_id:"+c.getInt(c.getColumnIndex("_id")));
        Log.i("info","name:"+c.getString(c.getColumnIndex("name")));
        Log.i("info","age:"+c.getInt(c.getColumnIndex("age")));
        Log.i("info","sex:"+c.getString(c.getColumnIndex("sex")));
        Log.i("info","__________________________________");
    }
    c.close();
}
db.close();

打出来的结果ID全是0，navicat 里面看到ID全是null。。

06-12 05:53:30.405 26973-26973/com.geekband.sqllitedemo01 I/info: _id:0
06-12 05:53:30.405 26973-26973/com.geekband.sqllitedemo01 I/info: name:张三
06-12 05:53:30.405 26973-26973/com.geekband.sqllitedemo01 I/info: age:18
06-12 05:53:30.405 26973-26973/com.geekband.sqllitedemo01 I/info: sex:女
06-12 05:53:30.405 26973-26973/com.geekband.sqllitedemo01 I/info: __________________________________
06-12 05:53:30.405 26973-26973/com.geekband.sqllitedemo01 I/info: _id:0
06-12 05:53:30.405 26973-26973/com.geekband.sqllitedemo01 I/info: name:李四
06-12 05:53:30.405 26973-26973/com.geekband.sqllitedemo01 I/info: age:19
06-12 05:53:30.405 26973-26973/com.geekband.sqllitedemo01 I/info: sex:女
06-12 05:53:30.405 26973-26973/com.geekband.sqllitedemo01 I/info: __________________________________
06-12 05:53:30.406 26973-26973/com.geekband.sqllitedemo01 I/info: _id:0
06-12 05:53:30.406 26973-26973/com.geekband.sqllitedemo01 I/info: name:王五
06-12 05:53:30.406 26973-26973/com.geekband.sqllitedemo01 I/info: age:20
06-12 05:53:30.406 26973-26973/com.geekband.sqllitedemo01 I/info: sex:男
06-12 05:53:30.406 26973-26973/com.geekband.sqllitedemo01 I/info: __________________________________
06-12 05:53:30.406 26973-26973/com.geekband.sqllitedemo01 I/info: _id:0
06-12 05:53:30.406 26973-26973/com.geekband.sqllitedemo01 I/info: name:张三
06-12 05:53:30.406 26973-26973/com.geekband.sqllitedemo01 I/info: age:18
06-12 05:53:30.406 26973-26973/com.geekband.sqllitedemo01 I/info: sex:女
06-12 05:53:30.406 26973-26973/com.geekband.sqllitedemo01 I/info: __________________________________
06-12 05:53:30.406 26973-26973/com.geekband.sqllitedemo01 I/info: _id:0
06-12 05:53:30.406 26973-26973/com.geekband.sqllitedemo01 I/info: name:李四
06-12 05:53:30.406 26973-26973/com.geekband.sqllitedemo01 I/info: age:19
06-12 05:53:30.406 26973-26973/com.geekband.sqllitedemo01 I/info: sex:女
06-12 05:53:30.406 26973-26973/com.geekband.sqllitedemo01 I/info: __________________________________
06-12 05:53:30.406 26973-26973/com.geekband.sqllitedemo01 I/info: _id:0
06-12 05:53:30.406 26973-26973/com.geekband.sqllitedemo01 I/info: name:王五
06-12 05:53:30.406 26973-26973/com.geekband.sqllitedemo01 I/info: age:20
06-12 05:53:30.406 26973-26973/com.geekband.sqllitedemo01 I/info: sex:男
06-12 05:53:30.406 26973-26973/com.geekband.sqllitedemo01 I/info: __________________________________
06-12 05:53:30.406 26973-26973/com.geekband.sqllitedemo01 I/info: _id:0
06-12 05:53:30.406 26973-26973/com.geekband.sqllitedemo01 I/info: name:张三
06-12 05:53:30.406 26973-26973/com.geekband.sqllitedemo01 I/info: age:18
06-12 05:53:30.406 26973-26973/com.geekband.sqllitedemo01 I/info: sex:女
06-12 05:53:30.406 26973-26973/com.geekband.sqllitedemo01 I/info: __________________________________
06-12 05:53:30.406 26973-26973/com.geekband.sqllitedemo01 I/info: _id:0
06-12 05:53:30.406 26973-26973/com.geekband.sqllitedemo01 I/info: name:李四
06-12 05:53:30.406 26973-26973/com.geekband.sqllitedemo01 I/info: age:19
06-12 05:53:30.406 26973-26973/com.geekband.sqllitedemo01 I/info: sex:女
06-12 05:53:30.406 26973-26973/com.geekband.sqllitedemo01 I/info: __________________________________
06-12 05:53:30.406 26973-26973/com.geekband.sqllitedemo01 I/info: _id:0
06-12 05:53:30.406 26973-26973/com.geekband.sqllitedemo01 I/info: name:王五
06-12 05:53:30.406 26973-26973/com.geekband.sqllitedemo01 I/info: age:20
06-12 05:53:30.406 26973-26973/com.geekband.sqllitedemo01 I/info: sex:男
06-12 05:53:30.406 26973-26973/com.geekband.sqllitedemo01 I/info: __________________________________
06-12 05:53:30.406 26973-26973/com.geekband.sqllitedemo01 I/info: _id:0
06-12 05:53:30.406 26973-26973/com.geekband.sqllitedemo01 I/info: name:张三
06-12 05:53:30.406 26973-26973/com.geekband.sqllitedemo01 I/info: age:18
06-12 05:53:30.406 26973-26973/com.geekband.sqllitedemo01 I/info: sex:女
06-12 05:53:30.406 26973-26973/com.geekband.sqllitedemo01 I/info: __________________________________
06-12 05:53:30.406 26973-26973/com.geekband.sqllitedemo01 I/info: _id:0
06-12 05:53:30.406 26973-26973/com.geekband.sqllitedemo01 I/info: name:李四
06-12 05:53:30.406 26973-26973/com.geekband.sqllitedemo01 I/info: age:19
06-12 05:53:30.406 26973-26973/com.geekband.sqllitedemo01 I/info: sex:女
06-12 05:53:30.406 26973-26973/com.geekband.sqllitedemo01 I/info: __________________________________
06-12 05:53:30.406 26973-26973/com.geekband.sqllitedemo01 I/info: _id:0
06-12 05:53:30.406 26973-26973/com.geekband.sqllitedemo01 I/info: name:王五
06-12 05:53:30.406 26973-26973/com.geekband.sqllitedemo01 I/info: age:20
06-12 05:53:30.407 26973-26973/com.geekband.sqllitedemo01 I/info: sex:男
06-12 05:53:30.407 26973-26973/com.geekband.sqllitedemo01 I/info: __________________________________
06-12 05:53:30.493 26973-27023/com.geekband.sqllitedemo01 D/OpenGLRenderer: Use EGL_SWAP_BEHAVIOR_PRESERVED: