Working with Input Views

Overview

Android has support for many different input controls for accepting input from the user. The common input controls include:

• Buttons
• Text Fields
• Checkboxes
• Radio Buttons
• Toggle Buttons
• Spinners
• Date and Time Pickers

Adding an input control to your UI is as simple as adding an XML element to your XML layout.

Checkboxes

Checkboxes allow the user to select one or more options from a set. Typically, you should present each checkbox option in a vertical list. Add them to the view:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">
    <CheckBox android:id="@+id/checkbox_meat"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/meat"
        android:onClick="onCheckboxClicked"/>
    <CheckBox android:id="@+id/checkbox_cheese"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/cheese"
        android:onClick="onCheckboxClicked"/>
</LinearLayout>

and then in the activity:

public void onCheckboxClicked(View view) {
    // Is the view now checked?
    boolean checked = ((CheckBox) view).isChecked();
    
    // Check which checkbox was clicked
    switch(view.getId()) {
        case R.id.checkbox_meat:
            if (checked)
                // Put some meat on the sandwich
            else
                // Remove the meat
            break;
        case R.id.checkbox_cheese:
            if (checked)
                // Cheese me
            else
                // I'm lactose intolerant
            break;
    }
}

Using this pattern you can manage the checkbox events and take the user input. Take a look at the Official Checkbox Guide for more details.

Radio Buttons

Radio buttons allow the user to select one option from a set. If it's not necessary to show all options side-by-side, use a spinner instead.

To create each radio button option, create a RadioButton in your layout. However, because radio buttons are mutually exclusive, you must group them together inside a RadioGroup. By grouping them together, the system ensures that only one radio button can be selected at a time.

<?xml version="1.0" encoding="utf-8"?>
<RadioGroup xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical">
    <RadioButton android:id="@+id/radio_pirates"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/pirates"
        android:onClick="onRadioButtonClicked"/>
    <RadioButton android:id="@+id/radio_ninjas"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/ninjas"
        android:onClick="onRadioButtonClicked"/>
</RadioGroup>

and within the activity:

public void onRadioButtonClicked(View view) {
    // Is the button now checked?
    boolean checked = ((RadioButton) view).isChecked();
    
    // Check which radio button was clicked
    switch(view.getId()) {
        case R.id.radio_pirates:
            if (checked)
                // Pirates are the best
            break;
        case R.id.radio_ninjas:
            if (checked)
                // Ninjas rule
            break;
    }
}

Check out the official radio buttons guide for more details.

Spinners

Spinners provide a quick way to select one value from a set of options. Create a spinner like any view and specify the android:entries attribute to specify the set of options:

<Spinner
         android:id="@+id/mySpinner"
         android:layout_width="wrap_content"
	 android:entries="@array/planets_arrays"
         android:prompt="@string/planets_prompt"
         android:layout_height="wrap_content" />

and then specify the string array of options in res/values/planets_array.xml:

<?xml version="1.0" encoding="utf-8"?>
<resources>
	<string-array name="planets_array">
		<item>Mercury</item>
		<item>Venus</item>
		<item>Earth</item>
		<item>Mars</item>
	</string-array>
</resources>

Get the selected item out a spinner using:

String value = spinner.getSelectedItem().toString();

Setting spinner item based on value (rather than item position):

public void setSpinnerToValue(Spinner spinner, String value) {
	int index = 0;
	SpinnerAdapter adapter = spinner.getAdapter();
	for (int i = 0; i < adapter.getCount(); i++) {
		if (adapter.getItem(i).equals(value)) {
			index = i;
		}
	}
	spinner.setSelection(index);
}

You can also load a spinner using an adapter for a dynamic source of options using an Adapter:

Spinner spinner = (Spinner) findViewById(R.id.spinner);
// Create an ArrayAdapter using the string array and a default spinner layout
ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(this,
        R.array.planets_array, android.R.layout.simple_spinner_item);
// Specify the layout to use when the list of choices appears
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
// Apply the adapter to the spinner
spinner.setAdapter(adapter);

Check out the Spinners guide for more details.

Also note that customizing or styling a spinner's text requires using a custom array adapter and layout file as explained in this answer.

References

• http://developer.android.com/guide/topics/ui/controls.html