Q-3: SeekBar in Android OR LinearLayout Usage (5 Marks)

Questions

a) What is the use seekbar in Android? Discuss various methods associated with seekbar.

OR

b) How do we use linear layout in android application? Explain with code.

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Answers

a) SeekBar in Android - Usage and Methods

Definition and Purpose

SeekBar is an Android UI widget that allows users to select a value from a continuous range by dragging a thumb along a horizontal track.

Primary Uses

• Volume Control: Audio/video volume adjustment
• Brightness Control: Screen brightness settings
• Progress Selection: Media playback position
• Range Selection: Price ranges, age selection
• Settings Adjustment: Various app settings
• Rating Systems: User rating input

Basic SeekBar Implementation

XML Layout:

<SeekBar
    android:id="@+id/seekBar"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:max="100"
    android:progress="50"
    android:layout_margin="16dp" />

<TextView
    android:id="@+id/textViewProgress"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Progress: 50"
    android:layout_gravity="center" />

Key Methods and Properties

1. Progress Management Methods

SeekBar seekBar = findViewById(R.id.seekBar);

// Set maximum value
seekBar.setMax(100);

// Set current progress
seekBar.setProgress(25);

// Get current progress
int currentProgress = seekBar.getProgress();

// Set secondary progress (for buffering indication)
seekBar.setSecondaryProgress(75);

// Get secondary progress
int secondaryProgress = seekBar.getSecondaryProgress();

// Increment progress by specific value
seekBar.incrementProgressBy(10);

// Increment secondary progress
seekBar.incrementSecondaryProgressBy(5);

2. Listener Methods

seekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
    @Override
    public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
        // Called when progress changes
        TextView textView = findViewById(R.id.textViewProgress);
        textView.setText("Progress: " + progress);
        
        // Check if change was initiated by user
        if (fromUser) {
            Log.d("SeekBar", "User changed progress to: " + progress);
        }
    }

    @Override
    public void onStartTrackingTouch(SeekBar seekBar) {
        // Called when user starts dragging the thumb
        Log.d("SeekBar", "Started tracking touch");
        // Pause auto-updates or other operations
    }

    @Override
    public void onStopTrackingTouch(SeekBar seekBar) {
        // Called when user stops dragging the thumb
        Log.d("SeekBar", "Stopped tracking touch");
        // Resume operations or save final value
    }
});

3. Appearance and Behavior Methods

// Enable/disable user interaction
seekBar.setEnabled(true);
seekBar.setEnabled(false);

// Set thumb drawable
seekBar.setThumb(ContextCompat.getDrawable(this, R.drawable.custom_thumb));

// Set progress drawable
seekBar.setProgressDrawable(ContextCompat.getDrawable(this, R.drawable.custom_progress));

// Set thumb offset
seekBar.setThumbOffset(10);

// Check if SeekBar is enabled
boolean isEnabled = seekBar.isEnabled();

Complete SeekBar Example

public class SeekBarActivity extends AppCompatActivity {
    private SeekBar volumeSeekBar, brightnessSeekBar;
    private TextView volumeText, brightnessText;
    private MediaPlayer mediaPlayer;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_seekbar);

        initializeViews();
        setupSeekBars();
        setupMediaPlayer();
    }

    private void initializeViews() {
        volumeSeekBar = findViewById(R.id.volumeSeekBar);
        brightnessSeekBar = findViewById(R.id.brightnessSeekBar);
        volumeText = findViewById(R.id.volumeText);
        brightnessText = findViewById(R.id.brightnessText);
    }

    private void setupSeekBars() {
        // Volume SeekBar
        volumeSeekBar.setMax(100);
        volumeSeekBar.setProgress(50);
        volumeSeekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
            @Override
            public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
                volumeText.setText("Volume: " + progress + "%");
                if (mediaPlayer != null && fromUser) {
                    float volume = progress / 100.0f;
                    mediaPlayer.setVolume(volume, volume);
                }
            }

            @Override
            public void onStartTrackingTouch(SeekBar seekBar) {
                // Optional: Show volume indicator
            }

            @Override
            public void onStopTrackingTouch(SeekBar seekBar) {
                // Optional: Save volume preference
                saveVolumePreference(seekBar.getProgress());
            }
        });

        // Brightness SeekBar
        brightnessSeekBar.setMax(255);
        brightnessSeekBar.setProgress(128);
        brightnessSeekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
            @Override
            public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
                brightnessText.setText("Brightness: " + (progress * 100 / 255) + "%");
                if (fromUser) {
                    adjustScreenBrightness(progress);
                }
            }

            @Override
            public void onStartTrackingTouch(SeekBar seekBar) {}

            @Override
            public void onStopTrackingTouch(SeekBar seekBar) {
                saveBrightnessPreference(seekBar.getProgress());
            }
        });
    }

    private void setupMediaPlayer() {
        mediaPlayer = MediaPlayer.create(this, R.raw.sample_audio);
        mediaPlayer.setLooping(true);
    }

    private void adjustScreenBrightness(int brightness) {
        WindowManager.LayoutParams layoutParams = getWindow().getAttributes();
        layoutParams.screenBrightness = brightness / 255.0f;
        getWindow().setAttributes(layoutParams);
    }

    private void saveVolumePreference(int volume) {
        SharedPreferences prefs = getSharedPreferences("settings", MODE_PRIVATE);
        prefs.edit().putInt("volume", volume).apply();
    }

    private void saveBrightnessPreference(int brightness) {
        SharedPreferences prefs = getSharedPreferences("settings", MODE_PRIVATE);
        prefs.edit().putInt("brightness", brightness).apply();
    }
}

Advanced SeekBar Features

Custom SeekBar with Range Selection:

public class RangeSeekBar extends View {
    private int minValue = 0;
    private int maxValue = 100;
    private int minThumbValue = 20;
    private int maxThumbValue = 80;
    
    // Custom implementation for range selection
    // Useful for price ranges, age ranges, etc.
}

Vertical SeekBar:

<SeekBar
    android:id="@+id/verticalSeekBar"
    android:layout_width="wrap_content"
    android:layout_height="200dp"
    android:rotation="270"
    android:transformPivotX="50dp"
    android:transformPivotY="50dp" />

---

b) LinearLayout Usage in Android Applications

Definition

LinearLayout is a ViewGroup that arranges its child views in a single direction, either horizontally or vertically.

Key Characteristics

• Sequential Arrangement: Children arranged in sequence
• Orientation: Horizontal or vertical orientation
• Weight Distribution: Proportional space allocation
• Gravity: Alignment control
• Simple Layout: Easy to understand and implement

Basic LinearLayout Structure

Vertical LinearLayout:

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:padding="16dp">

    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Title"
        android:textSize="24sp"
        android:textStyle="bold"
        android:gravity="center"
        android:layout_marginBottom="16dp" />

    <EditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="Enter your name"
        android:layout_marginBottom="12dp" />

    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Submit" />

</LinearLayout>

Horizontal LinearLayout:

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="horizontal"
    android:gravity="center"
    android:layout_margin="16dp">

    <Button
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:text="Cancel"
        android:layout_marginEnd="8dp" />

    <Button
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:text="OK"
        android:layout_marginStart="8dp" />

</LinearLayout>

Important Attributes

1. Orientation

android:orientation="vertical"    <!-- Stack vertically -->
android:orientation="horizontal"  <!-- Arrange horizontally -->

2. Layout Weight

android:layout_weight="1"  <!-- Proportional space allocation -->
android:layout_width="0dp" <!-- Use with weight for flexible width -->

3. Gravity

android:gravity="center"           <!-- Center children -->
android:gravity="center_vertical"  <!-- Center vertically -->
android:gravity="start|center_vertical" <!-- Left align + center vertically -->

Complete LinearLayout Example

activity_linear_layout.xml:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:padding="16dp"
    android:background="#F5F5F5">

    <!-- Header Section -->
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        android:gravity="center_vertical"
        android:background="#2196F3"
        android:padding="16dp"
        android:layout_marginBottom="16dp">

        <ImageView
            android:layout_width="48dp"
            android:layout_height="48dp"
            android:src="@drawable/ic_user"
            android:layout_marginEnd="16dp" />

        <LinearLayout
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:orientation="vertical">

            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="User Profile"
                android:textColor="@android:color/white"
                android:textSize="18sp"
                android:textStyle="bold" />

            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="Manage your account"
                android:textColor="@android:color/white"
                android:textSize="14sp" />

        </LinearLayout>

        <ImageView
            android:layout_width="24dp"
            android:layout_height="24dp"
            android:src="@drawable/ic_settings"
            android:layout_marginStart="16dp" />

    </LinearLayout>

    <!-- Form Section -->
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        android:background="@android:color/white"
        android:padding="16dp"
        android:layout_marginBottom="16dp">

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Personal Information"
            android:textSize="16sp"
            android:textStyle="bold"
            android:layout_marginBottom="16dp" />

        <EditText
            android:id="@+id/editTextName"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="Full Name"
            android:layout_marginBottom="12dp" />

        <EditText
            android:id="@+id/editTextEmail"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="Email Address"
            android:inputType="textEmailAddress"
            android:layout_marginBottom="12dp" />

        <EditText
            android:id="@+id/editTextPhone"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="Phone Number"
            android:inputType="phone"
            android:layout_marginBottom="16dp" />

        <!-- Horizontal buttons -->
        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="horizontal"
            android:gravity="end">

            <Button
                android:id="@+id/btnCancel"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="Cancel"
                android:style="?android:attr/buttonStyleSmall"
                android:layout_marginEnd="8dp" />

            <Button
                android:id="@+id/btnSave"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="Save"
                android:style="?android:attr/buttonStyleSmall" />

        </LinearLayout>

    </LinearLayout>

    <!-- Statistics Section with Weight Distribution -->
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        android:background="@android:color/white"
        android:padding="16dp">

        <LinearLayout
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:orientation="vertical"
            android:gravity="center">

            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="125"
                android:textSize="24sp"
                android:textStyle="bold"
                android:textColor="#4CAF50" />

            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="Posts"
                android:textSize="12sp" />

        </LinearLayout>

        <View
            android:layout_width="1dp"
            android:layout_height="match_parent"
            android:background="#E0E0E0" />

        <LinearLayout
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:orientation="vertical"
            android:gravity="center">

            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="1.2K"
                android:textSize="24sp"
                android:textStyle="bold"
                android:textColor="#2196F3" />

            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="Followers"
                android:textSize="12sp" />

        </LinearLayout>

        <View
            android:layout_width="1dp"
            android:layout_height="match_parent"
            android:background="#E0E0E0" />

        <LinearLayout
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:orientation="vertical"
            android:gravity="center">

            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="890"
                android:textSize="24sp"
                android:textStyle="bold"
                android:textColor="#FF9800" />

            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="Following"
                android:textSize="12sp" />

        </LinearLayout>

    </LinearLayout>

</LinearLayout>

MainActivity.java:

public class LinearLayoutActivity extends AppCompatActivity {
    private EditText editTextName, editTextEmail, editTextPhone;
    private Button btnSave, btnCancel;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_linear_layout);

        initializeViews();
        setupClickListeners();
    }

    private void initializeViews() {
        editTextName = findViewById(R.id.editTextName);
        editTextEmail = findViewById(R.id.editTextEmail);
        editTextPhone = findViewById(R.id.editTextPhone);
        btnSave = findViewById(R.id.btnSave);
        btnCancel = findViewById(R.id.btnCancel);
    }

    private void setupClickListeners() {
        btnSave.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                saveUserData();
            }
        });

        btnCancel.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                clearFields();
            }
        });
    }

    private void saveUserData() {
        String name = editTextName.getText().toString().trim();
        String email = editTextEmail.getText().toString().trim();
        String phone = editTextPhone.getText().toString().trim();

        if (validateInput(name, email, phone)) {
            // Save data logic
            Toast.makeText(this, "Data saved successfully", Toast.LENGTH_SHORT).show();
        }
    }

    private boolean validateInput(String name, String email, String phone) {
        if (name.isEmpty()) {
            editTextName.setError("Name is required");
            return false;
        }
        if (email.isEmpty()) {
            editTextEmail.setError("Email is required");
            return false;
        }
        return true;
    }

    private void clearFields() {
        editTextName.setText("");
        editTextEmail.setText("");
        editTextPhone.setText("");
    }
}

LinearLayout Advantages

• Simple to Use: Easy to understand and implement
• Predictable Layout: Clear visual hierarchy
• Weight Distribution: Flexible space allocation
• Performance: Good performance for simple layouts
• Nested Layouts: Can be nested for complex designs

LinearLayout Best Practices

• Avoid Deep Nesting: Use ConstraintLayout for complex layouts
• Use Weights Wisely: For proportional distribution
• Consider Orientation: Choose appropriate orientation
• Optimize Performance: Minimize layout hierarchy depth