implement MotionView.eventTime and VelocityTracker

This is needed to make androidx ViewPager work with touch input

src/api-impl/android/view/MotionEvent.java

@@ -1369,15 +1369,17 @@ public final class MotionEvent extends InputEvent {
 	int action;
 	float coord_x;
 	float coord_y;
+	long eventTime;
 
 	private MotionEvent() {
 	}
 
-	public MotionEvent(int source, int action, float coord_x, float coord_y) {
+	public MotionEvent(int source, int action, float coord_x, float coord_y, long eventTime) {
 		this.source = source;
 		this.action = action;
 		this.coord_x = coord_x;
 		this.coord_y = coord_y;
+		this.eventTime = eventTime;
 	}
 
 	@Override
@@ -1550,6 +1552,7 @@ public final class MotionEvent extends InputEvent {
 			ev.action = action;
 			ev.coord_x = x;
 			ev.coord_y = y;
+			ev.eventTime = eventTime;
 			return ev;
 		}
 	}
@@ -1816,7 +1819,7 @@ public final class MotionEvent extends InputEvent {
 	 */
 	@Override
 	public final long getEventTime() {
-		return System.currentTimeMillis();
+		return eventTime;
 	}
 
 	/**
@@ -1835,7 +1838,7 @@ public final class MotionEvent extends InputEvent {
 	 */
 	@Override
 	public final long getEventTimeNano() {
-		return System.currentTimeMillis() * 1000; // FIXME
+		return eventTime * 1000; // FIXME
 	}
 
 	/**
@@ -3030,7 +3033,7 @@ public final class MotionEvent extends InputEvent {
 		msg.append(", edgeFlags=0x").append(/*Integer.toHexString(getEdgeFlags())*/ "FIXME");
 		msg.append(", pointerCount=").append(pointerCount);
 		msg.append(", historySize=").append(/*getHistorySize()*/ "FIXME");
-		msg.append(", eventTime=").append(/*getEventTime()*/ "FIXME");
+		msg.append(", eventTime=").append(getEventTime());
 		msg.append(", downTime=").append(/*getDownTime()*/ "FIXME");
 		msg.append(", deviceId=").append(getDeviceId());
 		msg.append(", source=0x").append(Integer.toHexString(getSource()));

src/api-impl/android/view/VelocityTracker.java

@@ -6,15 +6,40 @@ public class VelocityTracker {
 		return new VelocityTracker();
 	}
 
-	public void addMovement(MotionEvent event) {}
+	private float startX;
+	private float startY;
+	private long startEventTime;
+	private float currentX;
+	private float currentY;
+	private long currentEventTime;
+
+	public void addMovement(MotionEvent event) {
+		if (event.getActionMasked() == MotionEvent.ACTION_DOWN) {
+			startX = currentX = event.getX();
+			startY = currentY = event.getY();
+			startEventTime = currentEventTime = event.getEventTime();
+		} else {
+			currentX = event.getX();
+			currentY = event.getY();
+			currentEventTime = event.getEventTime();
+		}
+	}
 
 	public void recycle() {}
 
 	public void computeCurrentVelocity(int units, float maxVelocity) {}
 	public void computeCurrentVelocity(int units) {}
 
-	public float getXVelocity(int id) {return 0.f;}
-	public float getYVelocity(int id) {return 0.f;}
+	public float getXVelocity(int id) {
+		if (currentEventTime == startEventTime)
+			return 0.f;
+		return (currentX - startX) / (currentEventTime - startEventTime) * 1000;
+	}
+	public float getYVelocity(int id) {
+		if (currentEventTime == startEventTime)
+			return 0.f;
+		return (currentY - startY) / (currentEventTime - startEventTime) * 1000;
+	}
 
 	public void clear() {}
 }

src/api-impl/android/view/ViewConfiguration.java

@@ -2,6 +2,9 @@ package android.view;
 
 import android.content.Context;
 
+/**
+ * default values are mainly based on AOSPs defaults. Does not account for scaling yet.
+ */
 public class ViewConfiguration {
 	
 	public static ViewConfiguration get(Context context) {
@@ -9,15 +12,15 @@ public class ViewConfiguration {
 	}
 
 	public int getScaledTouchSlop() {
-		return 0;
+		return 8;
 	}
 
 	public int getScaledMaximumFlingVelocity() {
-		return 0;
+		return 8000;
 	}
 
 	public int getScaledMinimumFlingVelocity() {
-		return 0;
+		return 50;
 	}
 
 	public static int getTapTimeout() {
@@ -29,7 +32,7 @@ public class ViewConfiguration {
 	}
 
 	public int getScaledPagingTouchSlop(){
-		return 0;
+		return 16;
 	}
 
 	public boolean hasPermanentMenuKey() {
@@ -45,6 +48,6 @@ public class ViewConfiguration {
 	}
 
 	public static float getScrollFriction() {
-		return 0.f;
+		return 0.015f;
 	}
 }