[AppBarLayout ] AppBarLayout does not support fling dispatch feature when sliding down

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**Description:** When AppBarLayout slides downwards, HeaderBehavior limits the maximum sliding distance, consumes all the sliding speed, is not distributed, and does not support nested sliding

**Expected behavior:** AppBarLayout support fling dispatch feature when sliding down

**Android API version:** 30

**Material Library version:** 1.5.0-alpha01

**Code In HeaderBehavior:**

```
final boolean fling(
CoordinatorLayout coordinatorLayout,
@NonNull V layout,
int minOffset,
int maxOffset,
float velocityY) {
if (flingRunnable != null) {
layout.removeCallbacks(flingRunnable);
flingRunnable = null;
}

if (scroller == null) {
scroller = new OverScroller(layout.getContext());
}

scroller.fling(
0,
getTopAndBottomOffset(), // curr
0,
Math.round(velocityY), // velocity.
0,
0, // x
minOffset,
maxOffset); // y

if (scroller.computeScrollOffset()) {
flingRunnable = new FlingRunnable(coordinatorLayout, layout);
ViewCompat.postOnAnimation(layout, flingRunnable);
return true;
} else {
onFlingFinished(coordinatorLayout, layout);
return false;
}
}
```

```
private class FlingRunnable implements Runnable {
private final CoordinatorLayout parent;
private final V layout;

FlingRunnable(CoordinatorLayout parent, V layout) {
this.parent = parent;
this.layout = layout;
}

@Override
public void run() {
if (layout != null && scroller != null) {
if (scroller.computeScrollOffset()) {
setHeaderTopBottomOffset(parent, layout, scroller.getCurrY());
// Post ourselves so that we run on the next animation
ViewCompat.postOnAnimation(layout, this);
} else {
onFlingFinished(parent, layout);
}
}
}
}
```

Start with the HeaderBehavior.fling implementation and FlingRunnable shown in the report, using the Android API 30 and Material Library 1.5.0-alpha01 context. Reproduce AppBarLayout sliding downward and verify that fling velocity is dispatched rather than consumed, with nested sliding supported and the expected maximum distance preserved.

Written by the indexing model from the issue text.