Android Spinner validation

问题:

I need to validate selected item of Spinner in Android.

I tried the following code, but it's not working.

if (Spinner1.getSelectedItem().toString().trim() == "Pick one") {
    Toast.makeText(CallWs.this, "Error", Toast.LENGTH_SHORT).show();
}

What is wrong with the code, and how can i fix it?

回答1:

Use .equals or .equalsIgnoreCase to compare two strings in java/android instead of ==.

Try this

if (Spinner1.getSelectedItem().toString().trim().equals("Pick one")) {
    Toast.makeText(CallWs.this, "Error", Toast.LENGTH_SHORT).show();
}

回答2:

Use equals("Pick one") and always use equals() method when checking for equality for String type in Java (unless you are checking for reference equality) as follows;

if (Spinner1.getSelectedItem().toString().trim().equals("Pick one")) {
    Toast.makeText(CallWs.this, "Error", Toast.LENGTH_SHORT).show();
}

What's wrong with you code is; you are using == which results in checking if Spinner1.getSelectedItem().toString() is the same reference as "Pick one" which will always be false since "Pick one" is a new String() instance

For details, check:

• string .equals() vs ==
• How to compare Strings

回答3:

Create a new layout called spinner_item.xml:

<?xml version="1.0" encoding="utf-8"?>

<TextView xmlns:android="http://schemas.android.com/apk/res/android"
    android:gravity="center_vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

inside your activity MainActivity.java initialize your spinner view:

Spinner mySpinner= (Spinner) findViewById(R.id.mySpinner);
ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(this, R.array.items_array, R.layout.spinner_item);
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
mySpinner.setAdapter(adapter);

Finally use the following method to validate your spinner:

boolean validateSpinner(Spinner spinner, String error){
        View selectedView = spinner.getSelectedView();
        if (selectedView != null && selectedView instanceof TextView) {
            TextView selectedTextView = (TextView) selectedView;
            if (selectedTextView.getText().equals("")) {
                selectedTextView.setError(error);
                Toast.makeText(this, error, Toast.LENGTH_LONG).show();
                return false;
            }
        }
        return true;
    }

回答4:

Try this..

else if (Spinner1.getSelectedItem().toString().trim().equals("Pick one")) {
                Toast.makeText(CallWs.this, "Error",
                        Toast.LENGTH_SHORT).show();

== always just compares two references (for non-primitives, that is) - i.e. it tests whether the two operands refer to the same object.

However, the equals method can be overridden - so two distinct objects can still be equal...... For more info

回答5:

Simply use this.

else if (Spinner1.getSelectedItem().toString().trim().equalsIgnoreCase("Pick one")) {
            Toast.makeText(CallWs.this, "Error",
                    Toast.LENGTH_SHORT).show();