我的while循环似乎有一个我找不到的问题。当我运行程序时，它表明它可以运行，但是什么也没有发生。帮助。
public class DatabaseHandler extends SQLiteOpenHelper {
// Database Version
public static final int DATABASE_VERSION = 1;
public static final String DATABASE_NAME = "spinnerExample";
private final Context myContext;
private SQLiteDatabase myDataBase;
// Database Name
// Labels table name
public static final String TABLE_LABELS = "labels"; //<<<< Made public
public static final String TABLE_LABELS1= "labels1";
public static final String TABLE_LABELS2= "labels2";
// Labels Table Columns names
public static final String KEY_ID4 = "input_label";
public static final String KEY_ID12 = "id2"; //<<<< Made public
public static final String KEY_ID = "id";
public static final String KEY_99 = "sno"; //<<<< Made public//<<<< Made public
public static final String KEY_NAME = "name"; //<<<< made public
public static final String KEY_ID1 = "id1"; //<<<< Made public
public static final String KEY_NAME1 = "name1";
public static final String KEY_1 = "number"; //<<<< Made public
public static final String KEY_2 = "outletname"; //<<<< made public
public static final String KEY_3 = "sunday"; //<<<< Made public
public static final String KEY_4 = "monday";
public static final String KEY_5 = "tuesday";
public static final String KEY_6 = "wednesday";
public static final String KEY_7 = "thursday";
public static final String KEY_8 = "saturday";
public static final String KEY_9 = "closed";
public static final String KEY_10 = "calling";
public static final String KEY_11 = "id3";
public static final String ROUTE= "route";
public DatabaseHandler(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
myDataBase = this.getWritableDatabase();
this.myContext = context;
}
// Creating Tables
@Override
public void onCreate(SQLiteDatabase db) {
//boolean dbExist = checkDataBase();
// Category table create query
String CREATE_CATEGORIES_TABLE = "CREATE TABLE " + TABLE_LABELS + "("+ KEY_99 + " INTEGER,"
+ ROUTE + " TEXT," + KEY_ID + " TEXT," + KEY_NAME + " TEXT)";
String CREATE_CATEGORIES_TABLE1 = "CREATE TABLE " + TABLE_LABELS1 + "("
+ KEY_ID1+ " TEXT," + KEY_NAME1+ " TEXT)";
String CREATE_CATEGORIES_TABLE2 = "CREATE TABLE " + TABLE_LABELS2 + "("
+ KEY_11+ " INTEGER PRIMARY KEY AUTOINCREMENT," + KEY_1+ " TEXT," + KEY_2+ " TEXT," + KEY_3+ " TEXT)";
db.execSQL(CREATE_CATEGORIES_TABLE);
db.execSQL(CREATE_CATEGORIES_TABLE1);
db.execSQL(CREATE_CATEGORIES_TABLE2);
}
// Upgrading database
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// Drop older table if existed
db.execSQL("DROP TABLE IF EXISTS " + TABLE_LABELS);
db.execSQL("DROP TABLE IF EXISTS " + TABLE_LABELS1);
db.execSQL("DROP TABLE IF EXISTS " + TABLE_LABELS2);
// Create tables again
onCreate(db);
}
/**
* Inserting new lable into lables table
* */
public void insertlabel(String text,String id9,String id, String label) {
SQLiteDatabase db = this.getWritableDatabase();
ContentValues cv = new ContentValues();
cv.put(KEY_99,text);
cv.put(ROUTE,id9);
cv.put(KEY_ID,id);
cv.put(KEY_NAME,label);
db.insert(TABLE_LABELS,null,cv);
db.close();
}
public void insertLabel(String message1, String message2,String message3){
SQLiteDatabase db = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(KEY_1, message1);
values.put(KEY_2, message2);
values.put(KEY_3,message3);
// Inserting Row
db.insert(TABLE_LABELS2, null, values);
//db.close(); // Closing database connection
}
public void insertLabel1(String label){
SQLiteDatabase db = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(KEY_NAME1, label);
db.insert(TABLE_LABELS1, null, values);
//db.close(); // Closing database connection
}
public void insertLabel2(String label){
SQLiteDatabase db = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(KEY_NAME, label);
db.insert(TABLE_LABELS, null, values);
db.close(); // Closing database connection
}
public Cursor getAllLabelsForSpinner1AsCursor() {
String[] columns = new String[]{"rowid AS _id, *"}; // Need _id column for SimpleCursorAdapter
return this.getWritableDatabase().query(TABLE_LABELS,columns,null,null,null,null,null);
}
public Cursor getAllLabelsForSpinner2AsCursor(String keyFromSinner1) {
String[] columns = new String[]{"rowid AS _id, *"}; // Need _id column for SimpleCursorAdapter
return this.getWritableDatabase().query(
TABLE_LABELS,columns,
DatabaseHandler.ROUTE + " LIKE ?",
new String[]{keyFromSinner1+"%"},
null,null,null
);
}
public Cursor getAllLabelsForSpinner3AsCursor(String keyFromSpinner2) {
String[] columns = new String[]{"rowid AS _id, *"}; // Need _id column for SimpleCursorAdapter
return this.getWritableDatabase().query(
TABLE_LABELS,columns,
DatabaseHandler.ROUTE + " LIKE ?",
new String[]{keyFromSpinner2 + "%"},
null,null,null);
}
}
答案 0 :(得分：1)
从中的行尾删除分号
while (!"Done".equals(answer));
分号本身就是一个空语句，它成为while循环的主体。结果，花括号中的块不再属于您的while循环。
在IDE中使用自动格式化/缩进会显示问题。它会将分号放在缩进的下一行。
答案 1 :(得分：1)
我测试了您的代码，并与上述问题一起在行尾添加了冒号：while (!"Done".equals(answer));，您使用“完成”一词停止程序的代码无法正常工作。
您每次都要两次检查“完成”字词，尽管只需要检查一次即可。
System.out.println("Enter the value: (Type 'done' to stop)");
Scanner input = new Scanner(System.in);
String answer = input.next();
while (!answer.equalsIgnoreCase("done")) {
char ch1 = answer.charAt(0);
if ((ch1 >= '0' && ch1 <= '9'))
System.out.println("Number");
else if ((ch1 >= 'a' && ch1 <= 'z'))
System.out.println("Small Character");
else if ((ch1 >= 'A' && ch1 <= 'Z'))
System.out.println("Capital Character");
else
System.out.println("Symbol");
System.out.println("Enter the value: (Type 'done' to stop)");
answer = input.next();
}
答案 2 :(得分：0)
除了while循环中的空语句外，您还一起使用nextLine()和next()。调用next()并不会占用行尾的换行符，这会导致后面的nextLine()仅读取换行符。除非您以相同的方式读取每一行，否则您将无法停止循环。