drawing view in Android using Java

To create a drawing view in Android using Java, you can follow a similar approach as the Kotlin example but translated into Java. Here’s how you can implement a basic drawing view with all features in Java:

1. CustomDrawView.java: This is the custom view class for drawing.

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;

public class CustomDrawView extends View {
    private Paint mPaint;
    private Path mPath;
    private Bitmap mBitmap;
    private Canvas mCanvas;
    private final int mBackgroundColor = Color.WHITE;
    private final float mBrushSize = 8f;

    public CustomDrawView(Context context, AttributeSet attrs) {
        super(context, attrs);
        mPaint = new Paint();
        mPath = new Path();
        mPaint.setAntiAlias(true);
        mPaint.setColor(Color.BLACK);
        mPaint.setStyle(Paint.Style.STROKE);
        mPaint.setStrokeJoin(Paint.Join.ROUND);
        mPaint.setStrokeWidth(mBrushSize);
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);
        mBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
        mCanvas = new Canvas(mBitmap);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        canvas.drawColor(mBackgroundColor);
        canvas.drawPath(mPath, mPaint);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        float touchX = event.getX();
        float touchY = event.getY();

        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                mPath.moveTo(touchX, touchY);
                break;
            case MotionEvent.ACTION_MOVE:
                mPath.lineTo(touchX, touchY);
                break;
            case MotionEvent.ACTION_UP:
                mPath.lineTo(touchX, touchY);
                mCanvas.drawPath(mPath, mPaint);
                mPath.reset();
                break;
            default:
                return false;
        }

        invalidate();
        return true;
    }

    public void clearDrawing() {
        mPath.reset();
        mCanvas.drawColor(mBackgroundColor);
        invalidate();
    }

    public void setBrushColor(int color) {
        mPaint.setColor(color);
    }

    public void setBrushSize(float size) {
        mPaint.setStrokeWidth(size);
    }
}

2. activity_main.xml: Include the custom view in your layout.

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <your.package.name.CustomDrawView
        android:id="@+id/customDrawView"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</RelativeLayout>

Make sure to replace your.package.name with your actual package name.

3. MainActivity.java: Initialize your custom view and add any additional features as needed.

import android.os.Bundle;
import androidx.appcompat.app.AppCompatActivity;

public class MainActivity extends AppCompatActivity {
    private CustomDrawView customDrawView;

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

        customDrawView = findViewById(R.id.customDrawView);
        // Example: Set brush color
        // customDrawView.setBrushColor(Color.RED);
    }
}

This setup provides a basic drawing view. You can extend it with more features like undo/redo, saving the drawing, adding text, shapes, and much more by leveraging the Paint and Canvas classes.