How to draw a line in Android?

This example demonstrates how do I draw a line in android.

Step 1 − Create a new project in Android Studio, go to File ⇒ New Project and fill all required details to create a new project.

Step 2 − Add the following code to res/layout/activity_main.xml.

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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"
   android:id="@+id/relativeLayout"
   tools:context=".MainActivity">
   <ImageView
      android:id="@+id/imageView"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_centerInParent="true"/>
   <Button
      android:id="@+id/button"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="Draw Line"
      android:layout_alignParentBottom="true"
      android:layout_centerHorizontal="true"
      android:layout_marginBottom="70dp"/>
</RelativeLayout>

Step 3 − Add the following code to src/MainActivity.java

import android.content.Context;
import android.content.res.Resources;
import android.graphics.Color;
import android.graphics.Paint;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.RelativeLayout;
import android.graphics.Canvas;
import android.graphics.Bitmap;
public class MainActivity extends AppCompatActivity {
   Context context;
   Resources resources;
   RelativeLayout relativeLayout;
   Button button;
   ImageView imageView;
   @Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
      context = getApplicationContext();
      resources = getResources();
      relativeLayout = findViewById(R.id.relativeLayout);
      button = findViewById(R.id.button);
      imageView = findViewById(R.id.imageView);
      button.setOnClickListener(new View.OnClickListener() {
         @Override
         public void onClick(View view) {
            Bitmap bitmap = Bitmap.createBitmap(10, 700, Bitmap.Config.ARGB_8888);
            Canvas canvas = new Canvas(bitmap);
            canvas.drawColor(Color.RED);
            Paint paint = new Paint();
            paint.setColor(Color.RED);
            paint.setStyle(Paint.Style.STROKE);
            paint.setStrokeWidth(8);
            paint.setAntiAlias(true);
            int offset = 50;
            canvas.drawLine(
               offset, canvas.getHeight() / 2, canvas.getWidth() - offset, canvas.getHeight() / 2, paint);
            imageView.setImageBitmap(bitmap);
         }
      });
      }
}

Step 4 - Add the following code to androidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
   package="app.com.sample">
   <application
      android:allowBackup="true"
      android:icon="@mipmap/ic_launcher"
      android:label="@string/app_name"
      android:roundIcon="@mipmap/ic_launcher_round"
      android:supportsRtl="true"
      android:theme="@style/AppTheme">
      <activity android:name=".MainActivity">
         <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
         </intent-filter>
      </activity>
   </application>
</manifest>

Let's try to run your application. I assume you have connected your actual Android Mobile device with your computer. To run the app from android studio, open one of your project's activity files and click Run  icon from the toolbar. Select your mobile device as an option and then check your mobile device which will display your default screen –

Click here to download the project code.