Memory heavy oval gradient


As you may know it is not possible to draw an oval radial gradient using regular Android API.

This is what I want to achieve:

<a href="https://i.stack.imgur.com/rNGjO.png" rel="nofollow"><img alt="Expected effect" class="b-lazy" data-src="https://i.stack.imgur.com/rNGjO.png" data-original="https://i.stack.imgur.com/rNGjO.png" src="https://etrip.eimg.top/images/2019/05/07/timg.gif" /></a>

So I implemented this solution: draw a regular radial gradient on a square bitmap and then this bitmap will get stretched by the view itself (idea found here: <a href="https://stackoverflow.com/a/3543899/649910" rel="nofollow">https://stackoverflow.com/a/3543899/649910</a>)

This works great however this solution takes a lot of memory, because of BitmapDrawable usage (see implementation details below).

Any ideas on how to avoid usage of such a big bitmap are welcome!

This my code:

public class OvalGradientView extends ImageView { private Drawable defaultBackgroundDrawable; public OvalGradientView(Context context) { super(context); init(); } public OvalGradientView(Context context, AttributeSet attrs) { super(context, attrs); init(); } public OvalGradientView(Context context, AttributeSet attrs, int defStyleAttr, Paint paint) { super(context, attrs, defStyleAttr); init(); } private void init() { setScaleType(ScaleType.FIT_XY); defaultBackgroundDrawable = getResources().getDrawable(R.drawable.default_background); } @Override protected void onLayout(boolean changed, int left, int top, int right, int bottom) { super.onLayout(changed, left, top, right, bottom); int width = getWidth(); int height = getHeight(); Rect currentBounds = defaultBackgroundDrawable.getBounds(); // check if we already have bitmap for these bounds if (currentBounds.right == width && currentBounds.bottom == height) { return; } // draw the drawable on square bitmap, it will be then stretched if needed to rectangular shape // as the view gets more rectangular defaultBackgroundDrawable.setBounds(0, 0, width, width); Bitmap defaultBackgroundBitmap = Bitmap.createBitmap(width, width, Bitmap.Config.ARGB_8888); Canvas canvas = new Canvas(defaultBackgroundBitmap); defaultBackgroundDrawable.draw(canvas); setImageBitmap(defaultBackgroundBitmap); } }

And this is the drawable XML - default_background

<shape xmlns:android="http://schemas.android.com/apk/res/android"> <gradient android:startColor="#ffffff" android:endColor="#ff6600" android:gradientRadius="50%p" android:type="radial" /> </shape


I wouldn't trust my own ability to create bitmaps like that, especially if they are full screen. Why not apply the xml shape as a background to the container view in xml as well? It will stretch to the proportions of the view if the width and height are match_parent

public class OvalGradientView extends ImageView { public OvalGradientView(Context context, AttributeSet attrs) { super(context, attrs); LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE); inflater.inflate(R.layout.my_sexy_gradient, this, true); } }


<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:background="@drawable/default_background"/>


I ended up with this implementation:

public class MyBackgroundView extends ImageView { public MyBackgroundView(Context context) { super(context); } public MyBackgroundView(Context context, AttributeSet attrs) { super(context, attrs); } public MyBackgroundView(Context context, AttributeSet attrs, int defStyleAttr) { super(context, attrs, defStyleAttr); } { setBackgroundResource(R.drawable.my_background); setScaleType(ScaleType.FIT_XY); } @Override protected void onLayout(boolean changed, int left, int top, int right, int bottom) { super.onLayout(changed, left, top, right, bottom); if (!changed) { return; } int width = right - left; int height = bottom - top; float aspectRatio = (float) width / height; if (aspectRatio > 1f) { setScaleX(aspectRatio); } else { setScaleY(1 / aspectRatio); } } }

where my_background is:

<shape xmlns:android="http://schemas.android.com/apk/res/android"> <gradient android:startColor="@color/my_background_start_color" android:endColor="@color/my_background_end_color" android:gradientRadius="@fraction/my_background_gradient_radius_percent" android:type="radial" /> </shape>

Width and height of this view are both match_parent.


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