A dependable dropdown means that your drop-down list is dependent on another factor or value, which will change the content of the dropdown. In android it is known as spinner.
Spinner
Spinner provides functionality to select a value from a list of multiple values. The first value is set as the default value in the spinner and upon clicking a dropdown list appears from where the user can select the desired value.
Implementation
If you don't know how to create a simple dropdown, then refer to this article, spinner in android
XML file
Add the following code in your XML file to include spinner in your Activity
<?xml version="1.0" encoding="utf-8"?> <androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools" android:id="@+id/layout" android:layout_width="match_parent" android:layout_height="match_parent" tools:context=".MainActivity"> <androidx.cardview.widget.CardView android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_gravity="center" app:layout_constraintBottom_toBottomOf="parent" app:layout_constraintTop_toTopOf="parent" tools:ignore="MissingConstraints"> <LinearLayout android:layout_width="match_parent" android:layout_height="match_parent" android:layout_margin="30sp" android:orientation="vertical"> <TextView android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_gravity="center" android:layout_marginVertical="10sp" android:text="Dependable dropdown" android:textSize="30sp" /> <TextView android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_gravity="center" android:layout_marginVertical="10sp" android:text="Select Gender" android:textSize="24sp" /> <Spinner android:id="@+id/spinner_gender" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_gravity="center" android:layout_marginVertical="5sp" /> <TextView android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_gravity="center" android:layout_marginVertical="10sp" android:text="Select Name" android:textSize="24sp" /> <Spinner android:id="@+id/spinner_name" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_gravity="center" android:layout_marginTop="5sp" android:layout_marginBottom="10sp" /> </LinearLayout> </androidx.cardview.widget.CardView> </androidx.constraintlayout.widget.ConstraintLayout> Resource XML file
Now the spinner is needed to be provided with the list of values for that we need to create a resource file in the resource file. Follow the following steps to create the resource file
- Right-click on your project
- From the menu go to New > Android Resource File
- Give a name to your file and press **Enter*
Add the following code into your resource file
<?xml version="1.0" encoding="utf-8"?> <resources> <string-array name="gender_type"> <item>Male</item> <item>Female</item> </string-array> <string-array name="girls"> <item>Priya</item> <item>Dolly</item> <item>Muskan</item> <item>Vaishnavi</item> </string-array> <string-array name="boys"> <item>Sumit</item> <item>Ujjwal</item> <item>Jaskirat</item> <item>Sukrut</item> <item>Prince</item> </string-array> </resources> JAVA file
To populate the spinner with a list of choices, you then need to specify a SpinnerAdapter in your Activity or Fragment source code. Following are the key classed:
- Spinner
- SpinnerAdapter
- AdapterView.OnItemSelectedListener
package com.example.spinner; import androidx.appcompat.app.AppCompatActivity; import android.os.Bundle; import android.view.View; import android.widget.AdapterView; import android.widget.ArrayAdapter; import android.widget.Spinner; import android.widget.Toast; import com.google.android.material.snackbar.BaseTransientBottomBar; import com.google.android.material.snackbar.Snackbar; public class MainActivity extends AppCompatActivity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); final Spinner spinner_gender = (Spinner)findViewById(R.id.spinner_gender); final Spinner spinner_name = (Spinner)findViewById(R.id.spinner_name); // Create an ArrayAdapter using the string array and // a default spinner layout ArrayAdapter<CharSequence> ad_gender = ArrayAdapter.createFromResource( this, R.array.gender_type, android.R.layout.simple_spinner_item); // Specify the layout to use when the list of // choices appears ad_gender.setDropDownViewResource( android.R.layout.simple_spinner_dropdown_item); // Apply the adapter to the spinner spinner_gender.setAdapter(ad_gender); spinner_gender.setOnItemSelectedListener( new AdapterView.OnItemSelectedListener() { @Override public void onItemSelected( AdapterView<?> adapterView, View view, int i, long l) { if (adapterView.getSelectedItem() .toString() .equals("Female")) { ArrayAdapter<CharSequence> ad_name = ArrayAdapter.createFromResource( getApplicationContext(), R.array.girls, android.R.layout .simple_spinner_item); spinner_name.setAdapter(ad_name); } else { ArrayAdapter<CharSequence> ad_name = ArrayAdapter.createFromResource( getApplicationContext(), R.array.boys, android.R.layout .simple_spinner_item); spinner_name.setAdapter(ad_name); } } @Override public void onNothingSelected( AdapterView<?> adapterView) { } }); spinner_name.setOnItemSelectedListener( new AdapterView.OnItemSelectedListener() { @Override public void onItemSelected( AdapterView<?> adapterView, View view, int i, long l) { Snackbar .make(findViewById(R.id.layout), adapterView.getSelectedItem() .toString() + " is a " + spinner_gender .getSelectedItem() .toString(), BaseTransientBottomBar .LENGTH_LONG) .show(); } @Override public void onNothingSelected( AdapterView<?> adapterView) { } }); } } The setOnItemSelectedListener will work whenever anything selection is made.
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