Drawing Paths

app/src/main/java/com/dragosholban/androiddrawing/DrawingView.java

@@ -0,0 +1,60 @@
package com.dragosholban.androiddrawing;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Path;
import android.os.Build;
import android.support.annotation.Nullable;
import android.support.annotation.RequiresApi;
import android.util.AttributeSet;
import android.view.View;

import java.util.ArrayList;

public class DrawingView extends View {

    private ArrayList<Path> paths = new ArrayList<>();

    public DrawingView(Context context) {
        super(context);
    }

    public DrawingView(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
    }

    public DrawingView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
    public DrawingView(Context context, @Nullable AttributeSet attrs, int defStyleAttr, int defStyleRes) {
        super(context, attrs, defStyleAttr, defStyleRes);
    }

    public void addPath(Path path) {
        paths.add(path);
    }

    public Path getLastPath() {
        if (paths.size() > 0) {
            return paths.get(paths.size() - 1);
        }

        return null;
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);

        for (Path path : paths) {
            Paint paint = new Paint();
            paint.setColor(0X80000000);
            paint.setStyle(Paint.Style.STROKE);
            paint.setStrokeWidth(3f);
            canvas.drawPath(path, paint);
        }
    }
}

app/src/main/java/com/dragosholban/androiddrawing/MainActivity.java

@@ -5,9 +5,14 @@

public class MainActivity extends AppCompatActivity {

    DrawingView drawingView;

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

        drawingView = findViewById(R.id.canvas);
        drawingView.setOnTouchListener(new TouchListener());
    }
}

app/src/main/java/com/dragosholban/androiddrawing/TouchListener.java

@@ -0,0 +1,35 @@
package com.dragosholban.androiddrawing;

import android.graphics.Path;
import android.view.MotionEvent;
import android.view.View;

public class TouchListener implements View.OnTouchListener {

    @Override
    public boolean onTouch(View view, MotionEvent event) {
        float x = event.getX();
        float y = event.getY();
        DrawingView drawingView = (DrawingView) view;
        Path path;

        switch (event.getAction() & MotionEvent.ACTION_MASK) {
            case MotionEvent.ACTION_DOWN:
                path = new Path();
                path.moveTo(x, y);
                drawingView.addPath(path);
                break;
            case MotionEvent.ACTION_MOVE:
                path = drawingView.getLastPath();
                if (path != null) {
                    path.lineTo(x, y);
                }
                break;
        }

        drawingView.invalidate();

        return true;
    }
}

app/src/main/res/layout/activity_main.xml

@@ -6,7 +6,7 @@
    android:layout_height="match_parent"
    android:background="#AFAFAF"
    tools:context=".MainActivity">
    <View
    <com.dragosholban.androiddrawing.DrawingView
        android:id="@+id/canvas"
        android:layout_width="0dp"
        android:layout_height="0dp"