Question

有人可以协助我使用带有光标的setMultiChoiceItems填充我的列表吗？我的AlertDialog弹出，带有标题和按钮，但列表中没有任何内容。我已经确认数据库中至少有一项，它应该显示在列表中，但目前没有。我认为这与我的光标有关。谢谢。

String isCheckedColumn;
String labelColumn;
Cursor cursor;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    mydb = new MyDBHandler(this);
    // CHECK INSERTION TO DATABASE WORKS AND PRINT TO LOGCAT
    mydb.insertAllergy("Nuts", "0");
    ArrayList<String> s = mydb.getAllAllergies();
    System.out.println(s.get(0));

    // INITIALIZE VARIABLES FOR LIST POPUP
    isCheckedColumn = "selected";
    labelColumn = "allergy";
}

/** LIST SELECTION POPUP */
public void selectAllergens() {
    AlertDialog.Builder builder = new AlertDialog.Builder(this);
    builder.setTitle("Select Allergens");
    builder.setMultiChoiceItems(cursor, isCheckedColumn, labelColumn, new DialogInterface.OnMultiChoiceClickListener() {
        @Override
        public void onClick(DialogInterface dialog, int selectedItemId, boolean isSelected) {
            if(isSelected) {
                System.out.println("onClick if");
            } else {
                System.out.println("onClick else");
            }
        }
    })
            .setPositiveButton("OK", new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int id) {

                }
            })
            .setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int id) {
                    dialog.dismiss();
                }
            });

    Dialog dialog = builder.create();

    dialog.show();
}

这是我的数据库帮助程序类MyDBHandler。我想也许这里应该有一个getCursor方法，所以当我需要初始化一个游标时，我可以这样做。没用。

public class MyDBHandler extends SQLiteOpenHelper {
// DATABASE INFORMATION
private static final int DATABASE_VERSION = 1;
private static final String DATABASE_NAME = "AllergiesDB.db";
private static final String TABLE_NAME = "allergies_list";
private static final String COLUMN_ID = "allergy_id";
private static final String COLUMN_ALLERGY = "allergy";
private static final String COLUMN_SELECTED = "selected";
private static final String SQL_CREATE_ENTRIES =
        "CREATE TABLE " + TABLE_NAME + " (" + COLUMN_ID + " INTEGER PRIMARY KEY, " +
        COLUMN_ALLERGY + " TEXT, " + COLUMN_SELECTED + " TEXT)";

// INITIALIZE DATABASE
public MyDBHandler(Context context) {
    super(context, DATABASE_NAME, null, DATABASE_VERSION);
}

@Override
public void onCreate(SQLiteDatabase db) {
    db.execSQL(SQL_CREATE_ENTRIES);
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME);
    onCreate(db);
}

public boolean insertAllergy(String allergy, String isChecked) {
    SQLiteDatabase db = this.getWritableDatabase();
    ContentValues contentValues = new ContentValues();
    contentValues.put(COLUMN_ALLERGY, allergy);
    contentValues.put(COLUMN_SELECTED, isChecked);
    db.insert(TABLE_NAME, null, contentValues);
    return true;
}

public Cursor getData(int id) {
    SQLiteDatabase db = this.getReadableDatabase();
    Cursor cursor = db.rawQuery("select * from " + TABLE_NAME + " where " + COLUMN_ID + "=" + id + "", null);
    return cursor;
}

public boolean updateAllergies(Integer id, String allergy, String isChecked) {
    SQLiteDatabase db = this.getWritableDatabase();
    ContentValues contentValues = new ContentValues();
    contentValues.put(COLUMN_ALLERGY, allergy);
    contentValues.put(COLUMN_SELECTED, isChecked);
    db.update(TABLE_NAME, contentValues, "id = ? ", new String[] {Integer.toString(id)});
    return true;
}

public Integer deleteAllergy(Integer id) {
    SQLiteDatabase db = this.getWritableDatabase();
    return db.delete(TABLE_NAME, "id = ? ", new String[] {Integer.toString(id)});
}

public ArrayList<String> getAllAllergies() {
    ArrayList<String> array_list = new ArrayList<>();

    SQLiteDatabase db = this.getReadableDatabase();
    Cursor cursor = db.rawQuery("select * from " + TABLE_NAME, null);
    cursor.moveToFirst();

    while(cursor.isAfterLast() == false) {
        array_list.add(cursor.getString(cursor.getColumnIndex(COLUMN_ALLERGY)));
        cursor.moveToNext();
    }

    return array_list;
}

public ArrayList<String> getSelectedAllergies() {
    ArrayList<String> array_list = new ArrayList<>();

    SQLiteDatabase db = this.getReadableDatabase();
    Cursor cursor = db.rawQuery("select * from " + TABLE_NAME, null);
    cursor.moveToFirst();

    while(cursor.isAfterLast() == false) {
        array_list.add(cursor.getString(cursor.getColumnIndex(COLUMN_SELECTED)));
        cursor.moveToNext();
    }

    return array_list;
}

public Cursor getCursor() {
    SQLiteDatabase db = this.getReadableDatabase();
    Cursor cursor = db.rawQuery("select * from " + TABLE_NAME, null);
    cursor.moveToFirst();
    return cursor;
}
}

这是弹出窗口的外观： AlertDialog Popup

在使用“ cursor = mydb.getCursor（）;”时出现错误。单击打开AlertDialog的按钮会产生错误。游标初始化位于MainActivity的onCreate方法中，因此初始化不会导致崩溃。原因是在setMultiChoiceItems中使用了游标，这使我相信游标没有正确初始化。

--------- beginning of crash
08-24 20:53:50.330 11277-11277/com.healthydreams.lpa.allergyscanner E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.healthydreams.lpa.allergyscanner, PID: 11277
java.lang.IllegalStateException: Could not execute method for android:onClick
    at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:390)
    at android.view.View.performClick(View.java:6294)
    at android.view.View$PerformClick.run(View.java:24770)
    at android.os.Handler.handleCallback(Handler.java:790)
    at android.os.Handler.dispatchMessage(Handler.java:99)
    at android.os.Looper.loop(Looper.java:164)
    at android.app.ActivityThread.main(ActivityThread.java:6494)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)
 Caused by: java.lang.reflect.InvocationTargetException
    at java.lang.reflect.Method.invoke(Native Method)
    at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:385)
    at android.view.View.performClick(View.java:6294) 
    at android.view.View$PerformClick.run(View.java:24770) 
    at android.os.Handler.handleCallback(Handler.java:790) 
    at android.os.Handler.dispatchMessage(Handler.java:99) 
    at android.os.Looper.loop(Looper.java:164) 
    at android.app.ActivityThread.main(ActivityThread.java:6494) 
    at java.lang.reflect.Method.invoke(Native Method) 
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438) 
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807) 
 Caused by: java.lang.IllegalArgumentException: column '_id' does not exist. Available columns: [allergy_id, allergy, selected]
    at android.database.AbstractCursor.getColumnIndexOrThrow(AbstractCursor.java:340)
    at android.widget.CursorAdapter.init(CursorAdapter.java:180)
    at android.widget.CursorAdapter.<init>(CursorAdapter.java:144)
    at android.support.v7.app.AlertController$AlertParams$2.<init>(AlertController.java:1009)
    at android.support.v7.app.AlertController$AlertParams.createListView(AlertController.java:1009)
    at android.support.v7.app.AlertController$AlertParams.apply(AlertController.java:965)
    at android.support.v7.app.AlertDialog$Builder.create(AlertDialog.java:982)
    at com.healthydreams.lpa.allergyscanner.MainActivity.selectAllergens(MainActivity.java:148)
    at com.healthydreams.lpa.allergyscanner.MainActivity.openProfiles(MainActivity.java:85)
    at java.lang.reflect.Method.invoke(Native Method) 
    at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:385) 
    at android.view.View.performClick(View.java:6294) 
    at android.view.View$PerformClick.run(View.java:24770) 
    at android.os.Handler.handleCallback(Handler.java:790) 
    at android.os.Handler.dispatchMessage(Handler.java:99) 
    at android.os.Looper.loop(Looper.java:164) 
    at android.app.ActivityThread.main(ActivityThread.java:6494) 
    at java.lang.reflect.Method.invoke(Native Method) 
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438) 
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)

Answer 1

我认为，当您第一次运行代码时，您会遇到colum_id异常。 column '_id' does not exist，应用程序将崩溃。这意味着您必须像这样_columnId创建主键。首先请看下划线。您可以在此处详细了解为什么。但是现在，请记住sqllite在主键列的开头需要_。 About "_id" field in Android SQLite

完成更改后，接下来您将在select query方法中遇到getCursor()的问题。有时*无法使用，因为它需要列的显式名称，因此请将查询更改为 select " + COLUMN_ID + "," + COLUMN_ALLERGY + "," + COLUMN_SELECTED + " from " + TABLE_NAME

我在下面发布了这些更改，我没有调用任何其他方法，因为我想为您提供一个在应用程序中看不到崩溃的开始。

private static final String COLUMN_ID = " _columnId";
private static final String COLUMN_ALLERGY = "allergy";
private static final String COLUMN_SELECTED = "selected";
private static final String SQL_CREATE_ENTRIES =
        "CREATE TABLE IF NOT EXISTS " + TABLE_NAME + " (" + COLUMN_ID " INTEGER PRIMARY KEY AUTOINCREMENT, " +
                COLUMN_ALLERGY + ", " + COLUMN_SELECTED  + ")";

......

public Cursor getCursor() {
    SQLiteDatabase db = this.getReadableDatabase();
    Cursor cursor = db.rawQuery("select " + COLUMN_ID + "," +  
    COLUMN_ALLERGY + "," + COLUMN_SELECTED + " from " + TABLE_NAME, 
    null);
    cursor.moveToFirst();
    return cursor;
}

您可以调用将在数据库中填充数据的方法，然后调用getCursor方法。一旦有了，条目将出现在对话框中。让我知道您是否遇到任何问题。

setMultiChoiceItems，其中光标未填充列表

1 个答案: