java - 如何停止允许字符串或字符的功能？（安卓）

问题描述

我正在创建一个库存应用程序，允许用户输入具有三个不同信息字段的输入项目。这些字段是项目名称、项目所有者和项目编号。

但是，当我在项目编号字段中输入字符串或字符时，应用程序会崩溃。我想通过不允许仅在此字段中输入字符来防止这种崩溃。我已经尝试了几个修复，但到目前为止似乎没有一个有效。

有没有专门检查字符串类型并防止使用它们？

这是我的 addItem 函数：

public class AddItem extends AppCompatActivity {

    // Setting up variable names for XML object items
    EditText mItemName;
    EditText mOwnerName;
    EditText mItemNum;
    Button mAddButton;

    @Override
    //Initializing object variables and the addButton setOnClickListener
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_add_item);
        mItemName = findViewById(R.id.itemName_input);
        mOwnerName = findViewById(R.id.owner_input);
        mItemNum = findViewById(R.id.num_input);
        mAddButton = findViewById(R.id.add_button);

        //This click listener sets up functionality for the add item button. The addItem method is called from the MyDBHelper class.
        mAddButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {

                //TESTING
                String itemName = mItemName.getText().toString().trim();
                String itemOwner = mOwnerName.getText().toString().trim();
                String itemNum = mItemNum.getText().toString().trim();

                //This IF/ELSE branch checks to see if any fields in AddItem are empty. If so, an error message displays. Else, it is entered into the database.
                if(itemName.equals("")||itemOwner.equals("")||itemNum.equals("")) {
                    Toast.makeText(AddItem.this, "Please enter data to all fields!", Toast.LENGTH_SHORT).show();
                }
                else {
                    MyDBHelper myDatabase = new MyDBHelper(AddItem.this);
                    myDatabase.addItem(mItemName.getText().toString().trim(), mOwnerName.getText().toString().trim(), Integer.valueOf(mItemNum.getText().toString().trim()));

                    //This will add functionality to return to the DisplayInventory Screen after pressing button.
                    Intent intent = new Intent(AddItem.this, DisplayInventory.class);
                    startActivity(intent);
                    finish();
                }
            }
        });


    }
}

这是该函数正在使用的数据库：

public class MyDBHelper extends SQLiteOpenHelper {

    // Setting up all variables that make up the columns in the database.
    private Context context;
    private static final String DATABASE_NAME = "InventoryList.db";
    private static final int DATABASE_VERSION = 1;
    private static final String TABLE_NAME = "my_list";
    private static final String COLUMN_ID = "_id";
    private static final String COLUMN_TITLE = "item_name";
    private static final String COLUMN_OWNER = "item_owner";
    private static final String COLUMN_NUM = "item_num";


    MyDBHelper(@Nullable Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
        this.context = context;
    }

    @Override
    //Initializing the Database
    public void onCreate(SQLiteDatabase sqLiteDatabase) {
        String query =
                "CREATE TABLE " + TABLE_NAME +
                        " (" + COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
                        COLUMN_TITLE + " TEXT, " +
                        COLUMN_OWNER + " TEXT, " +
                        COLUMN_NUM + " INTEGER);";
        sqLiteDatabase.execSQL(query);



    }

    @Override
    //This will make sure to erase the table if one already exists.
    public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {
        sqLiteDatabase.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME);
        onCreate(sqLiteDatabase);

    }

    //This method is adding functionality to add the item name, owner and number of items.
    void addItem(String itemName, String itemOwner, int numItem) {
        SQLiteDatabase db = this.getWritableDatabase();
        ContentValues cv = new ContentValues();

        cv.put(COLUMN_TITLE, itemName);
        cv.put(COLUMN_OWNER, itemOwner);
        cv.put(COLUMN_NUM, numItem);
        long result = db.insert(TABLE_NAME, null, cv);

        if (result == -1) {
            Toast.makeText(context, "Failed", Toast.LENGTH_SHORT).show();
        }
        else {
            Toast.makeText(context, "Item Added to Inventory!", Toast.LENGTH_SHORT).show();
        }
    }

    //This method sets up the functionality to search the entire database and read the data.
    Cursor readAllData() {
        String query = "SELECT * FROM " + TABLE_NAME;
        SQLiteDatabase db = this.getReadableDatabase();

        Cursor cursor = null;

        if (db != null) {
           cursor = db.rawQuery(query, null);
        }
        return cursor;
    }

    //This method allows the user to update the item's data. Values that will be updated are item name, owner and number of items.
    void updateData(String row_id, String item_name, String item_owner, String item_num) {
        SQLiteDatabase db = this.getWritableDatabase();
        ContentValues cv = new ContentValues();
        cv.put(COLUMN_TITLE, item_name);
        cv.put(COLUMN_OWNER, item_owner);
        cv.put(COLUMN_NUM, item_num);
        long result = db.update(TABLE_NAME, cv, "_id=?", new String[]{row_id});
    }

    void deleteItem(String row_id) {
        SQLiteDatabase db = this.getWritableDatabase();
        long result = db.delete(TABLE_NAME, "_id=?", new String[]{row_id});

    }

    void destroyInventory() {
        SQLiteDatabase db = this.getWritableDatabase();
        db.execSQL("DELETE FROM " + TABLE_NAME);
    }

}

标签： javaandroidsqliteandroid-studio

java - 如何停止允许字符串或字符的功能？（安卓）

问题描述

解决方案

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