allprojects {
    repositories {
        ...
        maven { url 'https://jitpack.io' }
    }
}

dependencies {
    ...
    compile 'com.github.Andreu35:BrushView:v.1.0'
    ...
}

<com.are.brushview.BrushView
  android:id="@+id/brushView"
  android:layout_width="220dp"
  android:layout_height="220dp"
  android:layout_gravity="center"
  android:layout_margin="20dp"
    app:brush_size="50"
    app:brush_alpha="255"
    app:brush_color="@color/colorPrimary"/>

public class MainActivity extends AppCompatActivity {
    private BrushView brushView;
    ...

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

        /**
         * Initialize Views
         */
        brushView = (BrushView) findViewById(R.id.brushView);
        ...
        
        /**
         * SeekBar Listeners
         */
        seekBarSize.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
            @Override
            public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
                txtSize.setText(String.valueOf(progress));
                brushView.setRadius(progress);
            }
        });

        seekBarAlpha.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
            @Override
            public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
                txtAlpha.setText(String.valueOf(progress));
                brushView.setAlphaValue(progress);
            }
        });

        gridView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                brushView.setColor(itemsColors.get(position).getColor());
            }
        });
    }
}