feat(android): add getScaledTouchSlop() to ListView

[m1ga]

JIRA:
https://jira.appcelerator.org/browse/TIMOB-27879

Optional Description:

Prevents the scrolling direction change to quickly. The current implementation will trigger an up/down change when you stop scrolling and your finger moves one pixel.

var win = Ti.UI.createWindow({backgroundColor: 'gray'});
var listView = Ti.UI.createListView({});
var sections = [];

var fruitSection = Ti.UI.createListSection({ headerTitle: 'Fruits'});
var fruitDataSet = [
    {properties: { height: 100,title: 'Apple'}},
    {properties: { height: 100,title: 'Apple'}},
    {properties: { height: 100,title: 'Apple'}},
    {properties: { height: 100,title: 'Apple'}},
    {properties: { height: 100,title: 'Apple'}},
    {properties: { height: 100,title: 'Apple'}},
    {properties: { height: 100,title: 'Apple'}},
    {properties: { height: 100,title: 'Banana'}},
    {properties: { height: 100,title: 'Banana'}},
    {properties: { height: 100,title: 'Banana'}},
    {properties: { height: 100,title: 'Banana'}},
    {properties: { height: 100,title: 'Banana'}},
    {properties: { height: 100,title: 'Banana'}},
    {properties: { height: 100,title: 'Banana'}},
    {properties: { height: 100,title: 'Banana'}},
    {properties: { height: 100,title: 'Banana'}},
    {properties: { height: 100,title: 'Banana'}},
    {properties: { height: 100,title: 'Banana'}},
    {properties: { height: 100,title: 'Banana'}},
];
fruitSection.setItems(fruitDataSet);
sections.push(fruitSection);

listView.appendSection(sections);
listView.addEventListener("scrolling",function(e){
	console.log(e.direction);
})
win.add(listView);
win.open();

[build]

	Fails
🚫	🔬 There are library changes, but no changes to the unit tests. That's OK as long as you're refactoring existing code, but will require an admin to merge this PR. Please see README.md#unit-tests for docs on unit testing.
🚫	Tests have failed, see below for more information.

	Warnings
⚠️	Commit 1dc9c5297285f8cbcdccddf1f54856306262cff2 has a message "scrollDamping" giving 2 errors: subject may not be empty type may not be empty
⚠️	Commit 46953a8eddc8f17a435ba8d75071f4336bc99b88 has a message "use touch slop" giving 2 errors: subject may not be empty type may not be empty

	Messages
📖	💾 Here's the generated SDK zipfile.
📖	🎉 Another contribution from our awesome community member, m1ga! Thanks again for helping us make Titanium SDK better. 👍
📖	🚨 This PR has one or more commits with warnings/errors for commit messages not matching our configuration. You may want to squash merge this PR and edit the message to match our conventions, or ask the original developer to modify their history.
📖	❌ 1 tests have failed There are 1 tests failing and 698 skipped out of 7371 total tests.

Tests:

Classname	Name	Time	Error
android.emulator.Titanium.App	pause/resume events (9)	8.895	Error: timeout of 5000ms exceeded at Titanium.<anonymous> (/ti-mocha.js:6535:53120)

Generated by 🚫 dangerJS against 2f89959

[jquick-axway]

@m1ga, I don't know if I like the idea of this. This effectively dampens all "scroll" events where it'll only fire if it has moved 5 pixels away from its last position. I'm curious what your use-case is.

[m1ga]

@jquick-axway check the JIRA description. The current implementation will fire up/down changes for every pixel and it will create some noise if you stop moving your finger but the the phone will recognize tiny changes and e.g. it will already show/hide your views because it thinks you've change direction. Just putting the finger on the screen will most of the time already fire a up/down event.
Default value can always be 1 so it behaves like before but with 5 the user scroll experience is better

[jquick-axway]

@m1ga, oh I see. Sorry about misunderstanding this. What you're doing makes sense.

My only feedback then is:

• We shouldn't hard-code it to 5 pixels. Instead, use Google's ViewConfiguration.getScaledTouchSlop() to get the pixel tolerance needed which is scaled based on device DPI.
• I don't think we need a new scrollDamping property. We can just hard-code it to use the touch-slop value like how Google does it internally with scroll views and drag-and-drop.

FYI: We use the touch-slop API to handle nested scrolling for Titanium's TextFields and TextAreas (link below). It works well and I haven't heard of any complaints.
TiUIEditText.java#L90-L93

What do you think?

[m1ga]

@jquick-axway didn't know about that method! Nice, updated the PR, remove the custom value. Works fine here

[jquick-axway]

CR: Pass

[ssjsamir]

FR Passed Tested using the test case mentioned above, able to see scrolling direction being more stable and not changing constantly (perviously just placing your finger on the screen was enough to trigger the scroll event)

Test Environment

MacOS Big Sur: 11.0 Beta
Xcode: 12.0 Beta 
Java Version: 1.8.0_242
Android NDK: 21.3.6528147
Node.js: 12.18.1
""NPM":"5.0.0","CLI":"8.0.0""
API29 Pixel XL emulator

[ssaddique]

Fix verified on build 9.1.0.v20200804082025.

Test environment

OS Ver:         10.15.3
Xcode Ver:      Xcode 11.6
Appc NPM:       5.0.0
Appc CLI:       8.0.0
Node Ver:       10.17.0
Java Ver:       1.8.0_162
Device:      Pixel 3a (API 30 - Android 11)