我是一名新手/学生，正在开发一个显示待办事项列表的应用项目。我一直在使用警报对话框来获取用户的输入并将后者存储在表中。当我扩展到2个对话框以获取有关任务和主题的信息时，发生以下错误：
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.zilunlin.bacpack, PID: 8118
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.zilunlin.bacpack/com.example.zilunlin.bacpack.MainActivity}: android.database.sqlite.SQLiteException: no such column: subject (code 1): , while compiling: SELECT _id, title, subject FROM tasks
#################################################################
Error Code : 1 (SQLITE_ERROR)
Caused By : SQL(query) error or missing database.
(no such column: subject (code 1): , while compiling: SELECT _id, title, subject FROM tasks)
#################################################################
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3254)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3350)
at android.app.ActivityThread.access$1100(ActivityThread.java:222)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1795)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:158)
at android.app.ActivityThread.main(ActivityThread.java:7229)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)
Caused by: android.database.sqlite.SQLiteException: no such column: subject (code 1): , while compiling: SELECT _id, title, subject FROM tasks
#################################################################
Error Code : 1 (SQLITE_ERROR)
Caused By : SQL(query) error or missing database.
(no such column: subject (code 1): , while compiling: SELECT _id, title, subject FROM tasks)
#################################################################
at android.database.sqlite.SQLiteConnection.nativePrepareStatement(Native Method)
at android.database.sqlite.SQLiteConnection.acquirePreparedStatement(SQLiteConnection.java:1058)
at android.database.sqlite.SQLiteConnection.prepare(SQLiteConnection.java:623)
at android.database.sqlite.SQLiteSession.prepare(SQLiteSession.java:588)
at android.database.sqlite.SQLiteProgram.<init>(SQLiteProgram.java:59)
at android.database.sqlite.SQLiteQuery.<init>(SQLiteQuery.java:37)
at android.database.sqlite.SQLiteDirectCursorDriver.query(SQLiteDirectCursorDriver.java:44)
at android.database.sqlite.SQLiteDatabase.rawQueryWithFactory(SQLiteDatabase.java:1454)
at android.database.sqlite.SQLiteDatabase.queryWithFactory(SQLiteDatabase.java:1301)
at android.database.sqlite.SQLiteDatabase.query(SQLiteDatabase.java:1172)
at android.database.sqlite.SQLiteDatabase.query(SQLiteDatabase.java:1340)
at com.example.zilunlin.bacpack.MainActivity.updateUI(MainActivity.java:128)
at com.example.zilunlin.bacpack.MainActivity.onCreate(MainActivity.java:36)
at android.app.Activity.performCreate(Activity.java:6876)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1135)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3207)
... 9 more
请注意，此错误不会直接检测到，只有在我运行调试时才会显现。
以下是我的MainActivity代码，特别是对话框
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case R.id.action_add_task:
final EditText taskEditText = new EditText(this);
AlertDialog dialog = new AlertDialog.Builder(this)
.setTitle("Add a new task")
.setMessage("What is it that you gotta do?")
.setView(taskEditText)
.setPositiveButton("Add", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
String task = String.valueOf(taskEditText.getText());
SQLiteDatabase db = mHelper.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(TaskContract.TaskEntry.COL_TASK_TITLE, task);
db.insertWithOnConflict(TaskContract.TaskEntry.TABLE,
null,
values,
SQLiteDatabase.CONFLICT_REPLACE);
db.close();
updateUI();
}
})
.setNegativeButton("Cancel", null)
.create();
dialog.show();
final EditText SubjectText = new EditText(this);
AlertDialog setSubject = new AlertDialog.Builder(this)
.setTitle("Add its subject")
.setMessage("What is its subject?")
.setView(SubjectText)
.setPositiveButton("Add", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface setSubject, int which) {
String subject = String.valueOf(SubjectText.getText());
SQLiteDatabase db = mHelper.getWritableDatabase();
ContentValues subjectvalues = new ContentValues();
subjectvalues.put(TaskContract.TaskEntry.SUBJECT_NAME, subject);
db.insertWithOnConflict(TaskContract.TaskEntry.TABLE,
null,
subjectvalues,
SQLiteDatabase.CONFLICT_REPLACE);
db.close();
updateUI();
}
})
.setNegativeButton("Cancel", null)
.create();
setSubject.show();
return true;
default:
return super.onOptionsItemSelected(item);
}}
这是db合约
import android.provider.BaseColumns;
public class TaskContract {
public static final String DB_NAME = "com.zilunlin.todolist.db";
public static final int DB_VERSION = 1;
public class TaskEntry implements BaseColumns {
public static final String TABLE = "tasks";
public static final String COL_TASK_TITLE = "title";
public static final String SUBJECT_NAME = "subject";
}
}
最后，这是db helper
public class TaskDbHelper extends SQLiteOpenHelper {
public TaskDbHelper(Context context) {
super(context, TaskContract.DB_NAME, null, TaskContract.DB_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
String createTable = "CREATE TABLE " + TaskContract.TaskEntry.TABLE + " ( " +
TaskContract.TaskEntry._ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
TaskContract.TaskEntry.COL_TASK_TITLE + " TEXT NOT NULL);" +
TaskContract.TaskEntry.SUBJECT_NAME + " TEXT NOT NULL);";
db.execSQL(createTable);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS " + TaskContract.TaskEntry.TABLE);
onCreate(db);
}
}
我理解这个问题可能会重复，但鉴于我目前对编程的理解，我无法充分转移答案。任何回复都将不胜感激。
PS：我关注了Aldo Ziflaj关于待办事项列表的有用教程。
答案 0 :(得分：0)
你添加了额外的分号......
更改了此
String createTable =“CREATE TABLE IF NOT EXISTS”+ TaskContract.TaskEntry.TABLE +“（”+ TaskContract.TaskEntry._ID +“INTEGER PRIMARY KEY AUTOINCREMENT”，+ TaskContract.TaskEntry.COL_TASK_TITLE +“TEXT NOT NULL，”+ TaskContract.TaskEntry.SUBJECT_NAME +“TEXT NOT NULL”“;