如何停止 function 允许字符串或字符？ （安卓）

Question

I'm creating an inventory app that allows users to enter enter items with three different information fields. These fields are item name, item owner and item number.

However, when I input a string or character into the item number field, the app crashes. I want to prevent this crashing by not allowing for characters to be entered in this field only. I've tried a several fixes, but none seem to have worked so far.

Is there anyway to specifically check for string types and prevent using them?

Here is my addItem function:

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();
                }
            }
        });


    }
}

Here is the database the function is using:

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);
    }

}

Answer 1

You need to use android:inputType="number" property in your xml for EditText for itemNumber . That way user won't be able to enter any character to that input field.