Create an application to draw line on the screen as user drag his finger.


MainActivity.java

package com.example.assignment20;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;

public class MainActivity extends AppCompatActivity {

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(new ScreenActivity(this));

    }

}

activity_main.xml

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

<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"

    xmlns:tools="http://schemas.android.com/tools"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    tools:context=".MainActivity"/>

package com.example.assignment20;

import android.content.Context;

import android.graphics.Canvas;

import android.graphics.Color;

import android.graphics.Paint;

import android.graphics.Path;

import android.view.MotionEvent;

import android.view.View;

ScreenActivity.java

public class ScreenActivity extends View {

    Paint paintBrush=new Paint(Paint.ANTI_ALIAS_FLAG);

    Path path=new Path();

    public ScreenActivity(Context context) {

        super(context);

        paintBrush.setColor(Color.RED);

        paintBrush.setStrokeWidth(5);

        paintBrush.setStyle(Paint.Style.STROKE);

    }

    @Override

    protected void onDraw(Canvas canvas) {

        super.onDraw(canvas);

        canvas.drawPath(path, paintBrush);

    }

    @Override

    public boolean onTouchEvent(MotionEvent event) {

        super.onTouchEvent(event);

        float x = event.getX();

        float y=event.getY();

        switch(event.getAction())

        {

            case MotionEvent.ACTION_DOWN:

                path.moveTo(x, y);

                return true;

            case MotionEvent.ACTION_MOVE:

                path.lineTo(x, y);

                break;

        }

        invalidate();

        return true;

    }

}

Output 

To download follow this link : Program 20