Android Question App stopping on click

Discussion in 'Android Questions' started by Erfan Kakaei, Jul 18, 2019.

  1. Erfan Kakaei

    Erfan Kakaei New Member

    I was wondering if anyone could help me with this.
    My app compiles just fine, but when I click on any button within it, it just stops and exits.
    P.S: The only code within the mentioned buttons is to change the text inside a label.
    As in:
    label.Text = "1"
  2. DonManfred

    DonManfred Expert Licensed User

    Check the log and post the full error. Without it is hard to give any advice.

    If you have a small testproject. Upload it. In the IDE use File->Export as zip and upload this zip.
    Erfan Kakaei likes this.
  3. mangojack

    mangojack Well-Known Member Licensed User

    I will take a wild shot ... Should the above code be Label1.Text = "1"

    If this does not solve you problem ... follow @DonManfred instructions so we can help you further .
    Erfan Kakaei likes this.
  4. Erfan Kakaei

    Erfan Kakaei New Member

    Well unfortunately I don't have access to the logs, but yes my project is small.
    Here it is:

    Attached Files:

  5. Erfan Kakaei

    Erfan Kakaei New Member

    Thank you sir, I just did.
  6. DonManfred

    DonManfred Expert Licensed User

    Connect your device with usb and use USB Debugging. It will list the log.
    The Error is "Empty String" in a math calculation
    In fact it is this code from you.
    lblSum.Text = lblSum.Text + "0"
    lblSum is empty at start. You are trying to do a math operation here.
    add 0 to lblSum.Text.

    To concat the value of lblSum.Text and the 0 (when pressing Button "1" seems wrong to me.
    lblSum.Text = lblSum.Text & "0"
    This was the case in all buttons.

    Please find a slightly changes example.
    i have changed
    - all occurances of
    lblSum.Text = lblSum.Text + "0"
    lblSum.Text = lblSum.Text & "0"
    to concat the String.
    - all other numberbuttons other than the 0 to match the right number. You did used 0 in all...

    Attached Files:

    mangojack and Erfan Kakaei like this.
  7. Erfan Kakaei

    Erfan Kakaei New Member

    Thank you very much sir, it's been solved.
    Now could you please tell me how I can set a number variable to Null?
    For example let's say there's an integer with the value 4 inside it, and i'd like to have it empty as if it was just created.
    And is the method the same as setting a string to Null?
  8. Erel

    Erel Administrator Staff Member Licensed User

    A number variable can never be Null. It is also a mistake to set a string variable to null.
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