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"