我在android Studio中有一个有关酒店的项目，它有两个表（Room，Customer）的数据库。 我尝试使用外键（Room_ID）创建客户表，但是出现错误。 我如何创建它？ 另一个问题，当我添加一个新房间并转到“显示房间”活动时，我添加的第一个房间没有显示，这是什么问题？
这是Database类扩展SqliteOpenHelper
public DatabaseHelper(Context context) {
super(context, "Hotel", null, 1);
}
@Override
public void onCreate(SQLiteDatabase db) {
db .execSQL(room.Create_table);
db .execSQL(customer.Create_table);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("drop table " + room.Table_Name);
db.execSQL("drop table " + customer.Table_Name);
onCreate(db);
}
public boolean insert_room (String name , String type , String price){
SQLiteDatabase db = getWritableDatabase() ;
ContentValues data = new ContentValues();
data.put(room.Col_Name,name);
data.put(room.Col_Type,type);
data.put(room.Col_Price,price);
return db.insert(room.Table_Name,null ,data) >0 ;
}
public boolean insert_customer (String name , String mobile , String
passport,int days,int room_id){
SQLiteDatabase db = getWritableDatabase() ;
ContentValues data = new ContentValues();
data.put(customer.Col_Name,name);
data.put(customer.Col_Passport,passport);
data.put(customer.Col_Mobile,mobile);
data.put(customer.Col_Days,days);
data.put(customer.Col_Room_ID,room_id);
return db.insert(customer.Table_Name,null ,data) >0 ;
}
public ArrayList<room> getAll_rooms(){
SQLiteDatabase db = getWritableDatabase() ;
ArrayList<room> rooms=new ArrayList<>();
Cursor cursor = db.rawQuery("select * from " +room.Table_Name ,null);
if (cursor.moveToFirst()){
while (cursor.moveToNext()){
int id=cursor.getInt(cursor.getColumnIndex(room.Col_Id));
String name =cursor.getString(cursor.getColumnIndex(room.Col_Name));
String type =cursor.getString(cursor.getColumnIndex(room.Col_Type));
String price =cursor.getString(cursor.getColumnIndex(room.Col_Price));
room r =new room(id,name,type,price);
rooms.add(r);
}
}
cursor.close();
return rooms;
}
public ArrayList<customer> getAll_customers(){
SQLiteDatabase db = getWritableDatabase() ;
ArrayList<customer> customers=new ArrayList<>();
Cursor cursor = db.rawQuery("select * from " +customer.Table_Name ,null);
if (cursor.moveToFirst()){
while (cursor.moveToNext()){
int id=cursor.getInt(cursor.getColumnIndex(customer.Col_Id));
String name =cursor.getString(cursor.getColumnIndex(customer.Col_Name));
int days =cursor.getInt(cursor.getColumnIndex(customer.Col_Days));
String mobile =cursor.getString(cursor.getColumnIndex(customer.Col_Mobile));
String passport =cursor.getString(cursor.getColumnIndex(customer.Col_Passport));
int room_id =cursor.getInt(cursor.getColumnIndex(customer.Col_Room_ID));
customer c =new customer(id,name,passport,mobile,days,room_id);
customers.add(c);
}
}
cursor.close();
return customers;
}
}
这是客户类别
public class customer {
int id ;
String name ;
String passport_num;
String mobile;
int num_ofDays;
int room_id ;
public static final String Col_Id = "id";
public static final String Col_Name = "name";
public static final String Col_Passport= "passport_num";
public static final String Col_Days= "num_ofDays";
public static final String Col_Mobile= "mobile";
public static final String Col_Room_ID= "room_id";
public static final String Table_Name= "Customer";
public static final String Create_table = " create table Customer(id integer primary key autoincrement ," +
" name text , passport_num text , mobile text , num_ofDays integer " +
" room_id integer , FOREIGN KEY(room_id) references Room (id))";
public customer() {
}
public customer(int id, String name, String passport_num, String mobile, int num_ofDays, int room_id) {
this.id = id;
this.name = name;
this.passport_num = passport_num;
this.mobile = mobile;
this.num_ofDays = num_ofDays;
this.room_id = room_id;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getPassport_num() {
return passport_num;
}
public void setPassport_num(String passport_num) {
this.passport_num = passport_num;
}
public String getMobile() {
return mobile;
}
public void setMobile(String mobile) {
this.mobile = mobile;
}
public int getNum_ofDays() {
return num_ofDays;
}
public void setNum_ofDays(int num_ofDays) {
this.num_ofDays = num_ofDays;
}
public int getRoom_id() {
return room_id;
}
public void setRoom_id(int room_id) {
this.room_id = room_id;
}
}
这是“添加客户信息”
public class AddCustomer extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_add_customer);
final DatabaseHelper db=new DatabaseHelper(this);
final Spinner type = findViewById(R.id.room_type_add);
final EditText name = findViewById(R.id.customer_name_add);
final EditText mobile = findViewById(R.id.mobile_num_add);
final EditText passport = findViewById(R.id.passport_num_add);
final EditText days = findViewById(R.id.num_days_add);
final Button add =findViewById(R.id.addCustomer);
final ArrayList<room> spData=db.getAll_rooms();
room_adapter_spinner adapter=new room_adapter_spinner(this,spData);
type.setAdapter(adapter);
add.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String Name = name.getText().toString();
String Mobile = mobile.getText().toString();
String Passport = passport.getText().toString();
String Days = days.getText().toString() ;
int Days_i = Integer.parseInt(Days);
int TYpe=(int) type.getSelectedItemId();
if (db.insert_customer(Name,Mobile,Passport,Days_i ,TYpe)) {
Intent i = new Intent(AddCustomer.this,ShowCustomers.class);
startActivity(i);
}
else Toast.makeText(AddCustomer.this, "error", Toast.LENGTH_SHORT).show();
}
});
}
}
这是添加房间课程
public class AddRoom extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_add_room);
final DatabaseHelper db = new DatabaseHelper(this);
final EditText name = findViewById(R.id.room_name_add);
final Spinner type = findViewById(R.id.room_type_add);
final EditText price = findViewById(R.id.room_price_add);
final Button add =findViewById(R.id.addRoom);
add.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String name_ = name.getText().toString();
String type_s= type.getSelectedItem().toString();
String price_ = price.getText().toString();
if (db.insert_room(name_,type_s,price_)) {
Intent i = new Intent(AddRoom.this,ShowRooms.class);
startActivity(i);
}
}
});
}
}
这是（显示房间）课程
public class ShowRooms extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_show_rooms);
final ListView list = findViewById(R.id.list_rooms);
DatabaseHelper db = new DatabaseHelper(this) ;
ArrayList<room> data = db.getAll_rooms();
room_adapter adapter = new room_adapter(this,data);
list.setAdapter(adapter);
}
}
当我运行项目时，我有这个错误
Caused by: android.database.sqlite.SQLiteException: unknown column "room_id" in foreign key definition (code 1): , while compiling: create table Customer(id integer primary key autoincrement , name text , passport_num text , mobile text , num_ofDays integer room_id integer , FOREIGN KEY(room_id) references Room (id))
at android.database.sqlite.SQLiteConnection.nativePrepareStatement(Native Method)
at android.database.sqlite.SQLiteConnection.acquirePreparedStatement(SQLiteConnection.java:882)
at android.database.sqlite.SQLiteConnection.prepare(SQLiteConnection.java:493)
at android.database.sqlite.SQLiteSession.prepare(SQLiteSession.java:588)
at android.database.sqlite.SQLiteProgram.<init>(SQLiteProgram.java:58)
at android.database.sqlite.SQLiteStatement.<init>(SQLiteStatement.java:31)
at android.database.sqlite.SQLiteDatabase.executeSql(SQLiteDatabase.java:1663)
at android.database.sqlite.SQLiteDatabase.execSQL(SQLiteDatabase.java:1594)
at com.example.the_hotel_project.DatabaseHelper.onCreate(DatabaseHelper.java:23)
at android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:252)
at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:164)
at com.example.the_hotel_project.DatabaseHelper.getAll_rooms(DatabaseHelper.java:54)
at com.example.the_hotel_project.AddCustomer.onCreate(AddCustomer.java:32)
at android.app.Activity.performCreate(Activity.java:5104)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
at android.app.ActivityThread.access$600(ActivityThread.java:141)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:5041)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
at dalvik.system.NativeStart.main(Native Method)
答案 0 :(得分：3)
Customer类的String Create_table中缺少“，”（逗号）。在num_ofDays之后。
应该是：
cleanStartTime = moment();
cleanEndTime = moment().add(100, 'days');
theDuration = moment.duration(cleanStartTime.diff(cleanEndTime)).humanize()
console.log(theDuration)
答案 1 :(得分：2)
对于第二个问题（请再次回答两个不同的问题），请依次呼叫moveToFirst()和while(moveToNext())。
调用moveToFirst()时，光标位于第一个值；调用moveToNext()时，光标位于第二个位置。这就是为什么您的列表从第二个值开始的原因。
您可以做的是调用moveToFirst()并反转while循环：
if (cursor.moveToFirst()) {
do {
int id = cursor.getInt(cursor.getColumnIndex(room.Col_Id));
String name = cursor.getString(cursor.getColumnIndex(room.Col_Name));
String type = cursor.getString(cursor.getColumnIndex(room.Col_Type));
String price = cursor.getString(cursor.getColumnIndex(room.Col_Price));
room r = new room(id, name, type, price);
rooms.add(r);
} while (cursor.moveToNext());
}
或检查计数并仅致电moveToNext()
if(cursor.getCount() != 0) {
while(cursor.moveToNext()){
int id = cursor.getInt(cursor.getColumnIndex(room.Col_Id));
String name = cursor.getString(cursor.getColumnIndex(room.Col_Name));
String type = cursor.getString(cursor.getColumnIndex(room.Col_Type));
String price = cursor.getString(cursor.getColumnIndex(room.Col_Price));
room r = new room(id, name, type, price);
rooms.add(r);
}
}
对getAll_customers()