在表中插入主键的问题
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【中文标题】在表中插入主键的问题【英文标题】：Problem in inserting primary Key in table 【发布时间】：2019-02-24 11:39:47 【问题描述】：我有 2 个表，corporate（用于存储登录信息）和 assignment（用于存储分配详细信息）。
Corporate 表中的列：id（主键自动增量）、uname、密码。 ID 不是从用户那里获取的。
分配表中的列：assignment_topic、assignment_content、total_marks、id（外键）、id_assignment（主键自增）。
信息流： 1. 登录用户 --> 除了检查是否有效用户，初始化 id(1000) 并返回它（searchId() 方法）。 2. 用户分配的UI输入细节 --> BackgroundTask ---> insertAssignment方法。
问题：我无法通过从公司表中检索 id（主键）来在分配表中插入 id（外键）。相关列显示为空。
尝试了以下方法：
-
正如您在 DatabaseHelper 类中看到的那样，我尝试了外键，但它不起作用，因此将其删除。
除上述之外，我还尝试通过 getter 和 setter 获取 id，能够在一定程度上做到这一点，但不知道数据在哪里中断。
由于我是 android 新手，如果你们能帮助我解决这个问题，那就太好了。
如果您需要我提供任何进一步的信息，请告诉我。
下面是必要的代码。
插入分配类：
public void SubmitData(View view)
String topic_assign = topic.getText().toString();
String topic_content_assign = topic_content.getText().toString();
String total_marks = t_marks.getText().toString();
String id = loginInfo.getId();
Log.e("assignment_id:",id);
BackgroundTask backgroundTask = new BackgroundTask(this);
backgroundTask.execute("add_assignment", topic_assign, topic_content_assign, total_marks,id);
BackgroundTask 类：
import android.app.Activity;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.os.AsyncTask;
import android.util.Log;
import android.widget.ListView;
import android.widget.Toast;
public class BackgroundTask extends AsyncTask<String, Teacher_Assignment, String>
private static final String TAG = " Background task";
LoginInfo loginInfo = new LoginInfo();
Activity activity;
ListView listView;
AssignmentAdapter assignmentAdapter;
Teacher_Assignment teacher_assignment = new Teacher_Assignment();
private Context context;
BackgroundTask(Context context)
this.context = context;
activity = (Activity)context;
@Override
protected String doInBackground(String... params)
String method = params[0];
DatabaseHelper databaseHelper = new DatabaseHelper(context);
if(method.equals("add_assignment"))
String topic_assignment = params[1];
String topic_content = params[2];
String total_marks = params[3];
String id = params[4];
SQLiteDatabase db = databaseHelper.getWritableDatabase();
databaseHelper.insertAssignment(db,topic_assignment,topic_content,total_marks, id);
Log.d(TAG,"inserted successfully");
else if(method.equals("get_info"))
listView = (ListView) activity.findViewById(R.id.list_assignment);
//DatabaseHelper databaseHelper = new DatabaseHelper(context);
SQLiteDatabase db = databaseHelper.getReadableDatabase();
Cursor cursor = databaseHelper.getInformation(db);
assignmentAdapter = new AssignmentAdapter(context, R.layout.activity_assignment_page_recycle_view);
String assignment_content;
while(cursor.moveToNext())
assignment_content = cursor.getString(cursor.getColumnIndex(teacher_assignment.Assignment_content));
Teacher_Assignment teacher_assignment = new Teacher_Assignment(assignment_content);
publishProgress(teacher_assignment);
return "get_info";
return "One row inserted";
@Override
protected void onPreExecute()
super.onPreExecute();
@Override
protected void onPostExecute(String result)
if (result.equals("get_info"))
listView.setAdapter(assignmentAdapter);
else
Toast.makeText(context, result, Toast.LENGTH_LONG).show();
protected void onProgressUpdate(Assignment_Page... values)
assignmentAdapter.add(values[2]);
DatabaseHelper 类：
package com.example.education;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.nfc.Tag;
import android.util.Log;
class DatabaseHelper extends SQLiteOpenHelper
LoginInfo loginInfo = new LoginInfo();
Teacher_Assignment assign1 = new Teacher_Assignment();
//Login table
private static final int DATABASE_VERSION = 41;
private static final String DATABASE_NAME = "userInfo.db";
private static final String TABLE_NAME = "corporate";
private static final String COLUMN_ID = "id";
private static final String COLUMN_UNAME = "uname";
private static final String COLUMN_PASSWORD = "password";
private static final String TABLE_ASSIGNMENT = "assignment";
//private static final String COLUMN_ID_ASSIGNMENT = "user_id";
private static final String ASSIGNMENT_TOPIC = "assignment_topic";
//private static final String COLUMN_NAME = COLUMN_UNAME;
private static final String ASSIGNMENT_CONTENT = "assignment_content";
private static final String ASSIGNMENT_TOTAL_MARKS = "total_marks";
private static final String ID_COLUMN_ASSIGNMENT = "id_assignment";
private static final String TABLE_STUDENT_SELECTION = "student_selection";
private static final String COLUMN_STUDENT_ID = "student_id";
private static final String COLUMN_CLASS_SEC = "class_sec";
private static final String COLUMN_STUDENT_NAME = "name";
private static final String COLUMN_TOTAL_MARKS = "total_marks";
private static final String COLUMN_STUDENT_MARKS = "student_score";
SQLiteDatabase db;
private static final String CREATE_TABLE = "CREATE TABLE IF NOT EXISTS " + TABLE_NAME + "("
+ COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " + COLUMN_UNAME + " TEXT NOT NULL, " + COLUMN_PASSWORD + " TEXT NOT NULL " + ")";
private static final String CREATE_ASSIGNMENT_TABLE = "CREATE TABLE IF NOT EXISTS " + TABLE_ASSIGNMENT + "("
+ ASSIGNMENT_TOPIC + " TEXT NOT NULL, " + ASSIGNMENT_CONTENT + " TEXT NOT NULL, "
+ ASSIGNMENT_TOTAL_MARKS + " TEXT NOT NULL, "
+ ID_COLUMN_ASSIGNMENT + " INTEGER PRIMARY KEY AUTOINCREMENT, "
+ COLUMN_ID + " TEXT " + ")";
//+ " FOREIGN KEY(" + COLUMN_ID + ") REFERENCES " + TABLE_NAME + " (id) "
public DatabaseHelper(Context context)
super(context, DATABASE_NAME, null, DATABASE_VERSION);
public void insertData()
db = this.getWritableDatabase();
ContentValues content = new ContentValues();
content.put(COLUMN_ID,1000);
content.put(COLUMN_UNAME, "akhil");
content.put(COLUMN_PASSWORD,"admin");
db.insert(TABLE_NAME, null, content);
db.close();
public String insertAssignment(SQLiteDatabase db,String topic, String assignment_content, String total_marks, String id)
db = this.getWritableDatabase();
ContentValues content1 = new ContentValues();
//id = searchId(COLUMN_UNAME);
content1.put(ASSIGNMENT_TOPIC, topic);
content1.put(ASSIGNMENT_CONTENT,assignment_content);
content1.put(ASSIGNMENT_TOTAL_MARKS,total_marks);
content1.put(COLUMN_ID, loginInfo.getId());
db.insert(TABLE_ASSIGNMENT, null, content1);
db.close();
return topic;
数据库截图：
【问题讨论】：
当您将 id 作为方法中的参数时，为什么要从 loginInfo 获取值？ 我将其作为参数，因为在我的后台任务中，我通过 logininfo.getid() 存储数据...您能告诉我另一种获取 id 的方法 您不应该只使用content1.put(COLUMN_ID, id); 而不是 content1.put(COLUMN_ID, loginInfo.getId());？
嗨迈克..我尝试使用 content1.put(COLUMN_ID, id);但仍然为空
【参考方案1】：
通过将数据从一个活动传递到另一个活动，然后调用 SearchId 函数解决了这个问题
【讨论】：
【参考方案2】：id值来自于在BackgroundTask中初始化的loginInfo实例：
class DatabaseHelper extends SQLiteOpenHelper
LoginInfo loginInfo = new LoginInfo();
如果 id 是通过//id = searchId(COLUMN_UNAME); 获取的，请检查 searchId 方法。
【讨论】：
不评论时 id = searchId(COLUMN_UNAME); ，正如您在数据库屏幕截图中看到的那样，该值是 not found 而不是 null searchId() 方法返回“未找到”。 好的，所以它采用了 id 的初始值。你能帮我解决这个问题吗？它与 columnindex 有关系吗？ 分享 searchId() 方法。 请在下面找到searchID()方法以及searchLogin方法()以上是关于在表中插入主键的问题的主要内容，如果未能解决你的问题，请参考以下文章