How make Bottombar with custom shape fab button?

Question

I want to make a bottombar with attach fab button like given below image. If anyone knows about that type of different shape button library with a bottom with fab then suggest to me.

The image is given below make a bottombar with fab like this.

Answer 1

It is just an idea the code can be improved.
You can change the shape of the FloatingActionButton with the shapeAppearanceOverlay attribute:

<com.google.android.material.floatingactionbutton.FloatingActionButton
    app:shapeAppearanceOverlay="@style/cutfab"
    ..>

with:

<style name="cutfab">
    <item name="cornerFamily">cut</item>
    <item name="cornerSize">15dp</item>
</style>

Then you can define the BottomAppBar in your layout:

<com.google.android.material.bottomappbar.BottomAppBar
    android:id="@+id/bottomAppBar"
    app:fabAlignmentMode="center"
    app:fabCradleVerticalOffset="14dp"
    app:fabCradleMargin="8dp" />

Finally you can apply to the BottomAppBar a TopEdgeTreatment. Something like:

BottomAppBar bar = findViewById(R.id.bar);
BottomAppBarTopEdgeTreatment topEdge = new BottomAppBarCutCornersTopEdge(
        bar.getFabCradleMargin(),
        bar.getFabCradleRoundedCornerRadius(),
        bar.getCradleVerticalOffset());
MaterialShapeDrawable babBackground = (MaterialShapeDrawable) bar.getBackground();

babBackground.setShapeAppearanceModel(
  babBackground.getShapeAppearanceModel()
  .toBuilder()
  .setTopEdge(topEdge)
  .build());

Where the BottomAppBarCutCornersTopEdge is something like:

public class BottomAppBarCutCornersTopEdge extends BottomAppBarTopEdgeTreatment {

    private final float fabMargin;
    private final float cradleVerticalOffset;

    BottomAppBarCutCornersTopEdge(
            float fabMargin, float roundedCornerRadius, float cradleVerticalOffset) {
        super(fabMargin, roundedCornerRadius, cradleVerticalOffset);
        this.fabMargin = fabMargin;
        this.cradleVerticalOffset = cradleVerticalOffset;
    }

    @Override
    @SuppressWarnings("RestrictTo")
    public void getEdgePath(float length, float center, float interpolation, ShapePath shapePath) {
        float fabDiameter = getFabDiameter();
        if (fabDiameter == 0) {
            shapePath.lineTo(length, 0);
            return;
        }

        float diamondSize = fabDiameter / 2f;
        float middle = center + getHorizontalOffset();

        float verticalOffsetRatio = cradleVerticalOffset / diamondSize;
        if (verticalOffsetRatio >= 1.0f) {
            shapePath.lineTo(length, 0);
            return;
        }

        shapePath.lineTo(middle - (fabMargin + diamondSize), 0);    
        shapePath.lineTo(middle - fabDiameter/3, (diamondSize - cradleVerticalOffset + fabMargin) * interpolation);    
        shapePath.lineTo(middle + fabDiameter/3, (diamondSize - cradleVerticalOffset + fabMargin) * interpolation);    
        shapePath.lineTo(middle + (fabMargin + diamondSize), 0);    
        shapePath.lineTo(length, 0);
    }

}

To obtain a better result you should extend the CutCornerTreatment, implementing in the getCornerPath method the same path used in the BottomAppBar and apply it to the FloatingActionButton.