Question

Quite new to coding for android but this issue has me tearing my hair out because it seems to make no sense at all…

I have an activity with four form elements in the layout: a CheckBox, two EditTexts and a Button.

When the user presses the button, it saves the content of the EditTexts as two preference values.

When the user presses the checkbox, it does the following:
If the checkbox is checked, load the preferences and store them into two variables.
Check if either of those variables contain empty strings after trimming them.
If so, show an error message, otherwise show a success message.

Essentially, the two text fields are used to set a pair of preferences which must not be empty when the checkbox is clicked.

It seems to work fine if I click the checkbox before pressing the button – error message or success message shown as appropriate.

If I press the save button and then click the checkbox, it always shows the success message regardless of the preferences.

Code follows (trimmed from the program as a whole)…

layout.xml

    <CheckBox android:id="@+id/cboxActive" android:text="Click me!" android:onClick="toggleActive" android:layout_width="wrap_content" android:layout_height="wrap_content" />

    <EditText android:id="@+id/editFrom" android:layout_width="fill_parent" android:layout_height="wrap_content" android:inputType="phone"><requestFocus /></EditText>

    <EditText android:id="@+id/editTo" android:layout_width="fill_parent" android:layout_height="wrap_content" android:inputType="phone"></EditText>

    <Button android:id="@+id/btnSave" android:onClick="savePrefs" android:text="Save" android:layout_width="120dp" android:layout_height="wrap_content" android:layout_gravity="center_horizontal" />

</LinearLayout>

main class:

public class AutoMessengerActivity extends Activity 
{
SharedPreferences settings;
    CheckBox cboxActive;
    EditText editFrom, editTo;

    boolean active;
    String from, to;

    @Override
    public void onCreate(Bundle savedInstanceState) 
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        editFrom = (EditText) findViewById(R.id.editFrom);
        editTo = (EditText) findViewById(R.id.editTo);

        showPrefsInUI();
    }

    private void loadPrefs()
    {
        //Load preferences
        settings = getPreferences(MODE_PRIVATE);   
        from = settings.getString("from", "");
        to = settings.getString("to", "");

    }

    private void showPrefsInUI()
    {
        loadPrefs();

        //Set UI elements to preference values
        editFrom.setText(from);
        editTo.setText(to);   
    }


    public void savePrefs(View view) 
    {
        SharedPreferences.Editor editor = settings.edit();
        editor.putString("from", editFrom.getText().toString());
        editor.putString("to", editTo.getText().toString());

        editor.commit();

        Toast.makeText(this, "Prefs saved!", Toast.LENGTH_SHORT).show();
    }


    public void toggleActive(View view) 
    { 

        if (cboxActive.isChecked())
        {
        loadPrefs();

            //This toast is for debugging
            //It shows the correct data in all circumstances...
        Toast.makeText(this, "F: " + from + "   T: " + to, Toast.LENGTH_SHORT).show();

            //This is the part that seems to fail if you save then click checkbox
        if (from.trim() == "" || to.trim() == "")
        {           
            Toast.makeText(this, "Error - Prefs not saved", Toast.LENGTH_LONG).show();
            cboxActive.setChecked(false);
        }
        else
        {
            Toast.makeText(this, "Success!", Toast.LENGTH_SHORT).show();
        }

        }
        else
        {
        Toast.makeText(this, "Unchecked!", Toast.LENGTH_SHORT).show();
        }

    }
}

Hopefully that code gives an idea of the problem and allows it to be replicated…

Answer 1

Oh god, how silly of me – Urban and jcxavier hit the nail on the head… I forgot about that damn annoying quirk of Java! Changed the line to

from.trim().equals("") || to.trim().equals("")

And it works fine!

For what it’s worth, that HAD actually crossed my mind briefly, but it was 2am when I tried equals and I got confused about requiring an Object as the parameter and ended up specifying null rather than “” – which didn’t work…