java.lang.NumberFormatException: null（Android Studio 中的错误）

Question

我在下面收到此错误。我正在从 firebase 和 sqlite 检索我的数据库浏览器。希望你们能帮我解决这个问题。

提前致谢！

这是我的Database.java:

public class Database extends SQLiteAssetHelper {

    private static final String DB_NAME="coolblogDB.db";
    private static final int DB_VER=1;


    public Database(Context context) { super(context, DB_NAME, null, DB_VER); }

    public List<Order> getCarts() {
        SQLiteDatabase db = getReadableDatabase();
        SQLiteQueryBuilder qb = new SQLiteQueryBuilder();

        String[] sqlSelect = {"ProductId", "ProductName", "Quantity", "Price", "Discount"};
        String sqlTable = "OrderDetail";

        qb.setTables(sqlTable);
        Cursor c = qb.query(db, sqlSelect, null, null, null, null, null);

        final List<Order> result = new ArrayList<>();
        if (c.moveToFirst()) {
            do {
                result.add(new Order(c.getString(c.getColumnIndex("ProductId")),
                        c.getString(c.getColumnIndex("ProductName")),
                        c.getString(c.getColumnIndex("Quantity")),
                        c.getString(c.getColumnIndex("Price")),
                        c.getString(c.getColumnIndex("Discount"))
                ));
            } while (c.moveToNext());
        }
        return result;
    }

    public void addToCart(Order order)
    {
        SQLiteDatabase db = getReadableDatabase();
        String query = String.format("INSERT INTO OrderDetail(ProductId,ProductName,Quantity,Price,Discount) VALUES('%s','%s','%s','%s','%s');",
                order.getProductId(),
                order.getProductName(),
                order.getQuantity(),
                order.getPrice(),
                order.getDiscount());
        db.execSQL(query);
    }

    public void cleanCart()
    {
        SQLiteDatabase db = getReadableDatabase();
        String query = String.format("DELETE FROM OrderDetail");
        db.execSQL(query);
    }
}

这是我的logcat:

10-15 13:48:34.439 12860-12860/com.example.mariamsyafiqah.coolblog2 E/AndroidRuntime: FATAL EXCEPTION: main Process: com.example.mariamsyafiqah.coolblog2, PID: 12860 java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.mariamsyafiqah.coolblog2/com.example.mariamsyafiqah.coolblog2.Cart}: java.lang.NumberFormatException: null at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2665) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726) at android.app.ActivityThread.-wrap12(ActivityThread.java) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:154) at android.app.ActivityThread.main(ActivityThread.java:6119) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776) Caused by: java.lang.NumberFormatException: null at java.lang.Integer.parseInt(Integer.java:483) at java.lang.Integer.parseInt(Integer.java:556) at com.example.mariamsyafiqah.coolblog2.Cart.loadListDrink(Cart.java:128) at com.example.mariamsyafiqah.coolblog2.Cart.onCreate(Cart.java:71) at android.app.Activity.performCreate(Activity.java:6679) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1118) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2618) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726) at android.app.ActivityThread.-wrap12(ActivityThread.java) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:154) at android.app.ActivityThread.main(ActivityThread.java:6119) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)

Answer 1

检查您的 Cart.java 第 128 行，如以下错误所述：

java.lang.NumberFormatException: null at java.lang.Integer.parseInt(Integer.java:483) at java.lang.Integer.parseInt(Integer.java:556) at com.example.mariamsyafiqah.coolblog2.Cart.loadListDrink(Cart.java:128) at

有一行是这样的：

int val = Integer.parseInt(stringValue);

如果您的 stringValue 为 null 或为空，这将引发错误。您需要先检查字符串是否是正确的数字

java.lang.NumberFormatException: null（Android Studio 中的错误）

java.lang.NumberFormatException: null (Error in Android Studio)

java

android

null

numberformatexception