Implementing Scrolling Behavior Like iPhone SMS App

Introduction

The iPhone SMS app is a classic example of well-designed scrolling behavior. The chat screen features a ScrollView that contains all the message bubbles, along with a TextField at the bottom for writing new messages. When the TextField is clicked, the keyboard appears, and everything scrolls upwards to make room for it. In this article, we will delve into how this behavior can be implemented on Android.

Understanding Apple’s Approach

Before we dive into the implementation details, let’s first understand Apple’s approach to implementing scrolling behavior like in the iPhone SMS app. According to Apple’s documentation, the screen should support the appearance of a keyboard by resizing the ScrollView when the keyboard appears while maintaining its content size.

However, this raises an interesting question: how does the message bubble area inside the ScrollView resize neatly along with the keyboard? Unfortunately, Apple’s approach doesn’t provide a straightforward solution to this problem. Instead, they suggest manually implementing the refitting behavior for the scrolling and resizing animations of both the message bubbles and the TextField.

Implementation on Android

Now that we have understood Apple’s approach, let’s move on to implementing scrolling behavior similar to the iPhone SMS app on Android.

Step 1: Create a Layout for the Chat Screen

First, we need to create a layout for the chat screen. We will use a ScrollView as the main container, along with two views: one for the message bubbles and another for the TextField.

<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    
    <!-- Message Bubble Area -->
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:weightSum="1">
        
        <!-- Message Bubbles -->
        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="vertical">
            
            <!-- Individual Message Bubble -->
            <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:gravity="center_horizontal"
                android:padding="16dp"
                android:orientation="vertical">
                
                <!-- Message Text -->
                <TextView
                    android:id="@+id/message_text"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:textSize="16sp"
                    android:textStyle="bold" />
                
                <!-- Message Timestamp -->
                <TextView
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:textSize="12sp" />
            </LinearLayout>
            
        </LinearLayout>
        
    </LinearLayout>
    
    <!-- TextField Area -->
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:weightSum="1">
        
        <!-- Individual TextView for the keyboard */
        <TextView
            android:id="@+id/keyboard_textview"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:textSize="16sp" />
    </LinearLayout>
    
</ScrollView>

Step 2: Add Event Listeners for Keyboard Appearance and Disappearance

Next, we need to add event listeners to our chat screen layout to handle keyboard appearance and disappearance.

public class ChatScreenActivity extends AppCompatActivity {
    
    private ScrollView scrollView;
    private TextView textView;
    private int keyboardHeight = 0;
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        
        setContentView(R.layout.activity_chat_screen);
        
        scrollView = findViewById(R.id.scrollView);
        textView = findViewById(R.id.keyboard_textview);
        
        // Set up event listener for keyboard appearance and disappearance
        Window window = getWindow();
        window.addFlags(WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE | WindowManager.LayoutParams.FLAG_DRAWS_SYSTEM_BAR_BACKGROUNDS);
        window.setSoftInputMode(WindowManager.LayoutParams.SOFT_INPUT_STATE_VISIBLE);
        textView.setOnFocusChangeListener(new View.OnFocusChangeListener() {
            @Override
            public void onFocusChange(View view, boolean focused) {
                if (focused) {
                    // Calculate keyboard height and update ScrollView's height
                    int screenHeight = getWindow().getDecorView().getHeight();
                    keyboardHeight = (int) (screenHeight * 0.2); // Assuming a 20% overlap
                    scrollView.setPadding(0, keyboardHeight, 0, 0);
                } else {
                    // Reset ScrollView's height when the TextField loses focus
                    scrollView.setPadding(0, 0, 0, 0);
                }
            }
        });
        
    }
    
    @Override
    protected void onResume() {
        super.onResume();
        
        // Update ScrollView's height when the activity resumes
        if (textView.hasFocus()) {
            int screenHeight = getWindow().getDecorView().getHeight();
            keyboardHeight = (int) (screenHeight * 0.2); // Assuming a 20% overlap
            scrollView.setPadding(0, keyboardHeight, 0, 0);
        }
    }
    
    @Override
    protected void onPause() {
        super.onPause();
        
        // Reset ScrollView's height when the activity pauses
        if (textView.hasFocus()) {
            int screenHeight = getWindow().getDecorView().getHeight();
            scrollView.setPadding(0, 0, 0, 0);
        }
    }
}

Conclusion

In this article, we have implemented scrolling behavior similar to the iPhone SMS app on Android. We created a layout for the chat screen using a ScrollView as the main container and two views: one for the message bubbles and another for the TextField.

We added event listeners to our chat screen layout to handle keyboard appearance and disappearance. When the TextField is focused, we calculated the keyboard height and updated the ScrollView’s height accordingly.

This implementation provides a basic example of how to implement scrolling behavior similar to the iPhone SMS app on Android. You can customize this code as per your requirements and add more features to create a fully functional chat screen application.

Last modified on 2024-04-20