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Merge pull request #46 from orionlee/fix_bottom_h_swipes
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More fix on bottom horizontal swipes detection
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@genious7
genious7 committed Dec 13, 2018
2 parents a6b2ef6 + 65743fa commit 2b7a3d0
Showing 1 changed file with 241 additions and 118 deletions.
359 changes: 241 additions & 118 deletions ...r/src/main/java/com/spicymango/fanfictionreader/activity/reader/StoryDisplayActivity.java
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Original file line number Diff line number Diff line change
Expand Up @@ -766,150 +766,273 @@ protected Cursor getFromDatabase(long storyId) {
* Utility to detect horizontal swipes at the bottom of a given view.
*/
private static abstract class BottomHorizontalSwipeListener implements View.OnTouchListener {
private static final String TAG = "FFR-HSwipe";
private static final String TAG = "FFR-HSwipe";

private static final boolean DEBUG_TOUCHES = true && BuildConfig.DEBUG;

// Given the listener should have a life cycle within the parent view
// Holding a reference to the view should not cause memory leak.
@NonNull
final View mParentView; // package scope to be used by inner class

@NonNull
private final FixedGestureDetectorCompat mDetector;


public BottomHorizontalSwipeListener(@NonNull View parentView) {
mParentView = parentView;
mDetector = new FixedGestureDetectorCompat(parentView.getContext(),
new GestureDetector.SimpleOnGestureListener() {
final float mOneInchInPx = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_IN,
1, parentView.getContext().getResources().getDisplayMetrics());

@Override
public boolean onFling(MotionEvent event1, MotionEvent event2, float vX, float vY) {
if (DEBUG_TOUCHES) {
String dbgMsg = "onFling - vX: " + vX + ", vY: " + vY
+ ", e1.X: " + (event1 != null ? event1.getX() : -1) + ", e2.X: " + event2.getX()
+ ", e1.Y: " + (event1 != null ? event1.getY() : -1) + ", e2.Y: " + event2.getY()
+ ", height: " + mParentView.getHeight()
+ ", e1: " + event1 + ", e2: " + event2;
Log.d(TAG, dbgMsg);
}

private static final boolean DEBUG_TOUCHES = true && BuildConfig.DEBUG;

// Given the listener should have a life cycle within the parent view
// Holding a reference to the view should not cause memory leak.
@NonNull
final View mParentView; // package scope to be used by inner class
// logic to support horizontal swipes at screen bottom

@NonNull
private final GestureDetectorCompat mDetector;

// to be used by mDetector.onFling() in case event1 is null, i.e., no down event
MotionEvent mCurrentStartEvent;

public BottomHorizontalSwipeListener(@NonNull View parentView) {
mParentView = parentView;
mDetector = new GestureDetectorCompat(parentView.getContext(),
new GestureDetector.SimpleOnGestureListener() {
final float mOneInchInPx = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_IN,
1, parentView.getContext().getResources().getDisplayMetrics());

@Override
public boolean onFling(MotionEvent event1, MotionEvent event2, float vX, float vY) {
// somehow event1 (start of a fling) is often null (i.e., no ACTION_DOWN)
// use the first action move as an approximation
final MotionEvent evStart = event1 != null ? event1 : mCurrentStartEvent;

if (evStart == null) {
Log.w(TAG, "onFling - false, cannot determine Start Event");
return false;
// accept fling on screen / view bottom only
if (mParentView.getHeight() - event2.getY() > mOneInchInPx) {
if (DEBUG_TOUCHES) {
Log.d(TAG, " onFling - false, not on screen bottom");
}
return false;
}

return doOnFling(evStart, event2, vX, vY);
// accept flings with only small vertical delta only
float absDeltaY = Math.abs(event2.getY() - event1.getY());
// Note: relatively large vertical leeway (1 in) is allowed here
// because somehow, truly horizontal swipes often are not processed
// i.e., those horizontal swipes are not passed to the parent OnTouchListener
// at all.
// The swipes that get registered tend to have some leeway.
if (absDeltaY > mOneInchInPx) {
if (DEBUG_TOUCHES) {
Log.d(TAG, " onFling - false, absDeltaY too large, absDeltaY: " + absDeltaY);
}
return false;
}

private boolean doOnFling(MotionEvent event1, MotionEvent event2, float vX, float vY) {
// accept flings with big enough horizontal delta
// Note: for the rule with more lenient (0.25in) range when event1 is not ACTION_DOWN
// This is to address cases that (many) MotionEvent are not passed to the detector.
// In those cases, initial ACTION_DOWN are rarely supplied, so as some other
// events. The net result is that in a typical swipe, the deltaX derived by
// the supplied MotionEvent tends to be much smaller than the actual user swipe.
// Empirically, even for a swipe over 1inch, it is not unusual for the deltaX
// be as small as 0.2in (due to missing MotionEvents)
float deltaX = event2.getX() - event1.getX();
if (!( Math.abs(deltaX) > mOneInchInPx / 2 ||
(MotionEvent.ACTION_DOWN != event1.getActionMasked() &&
Math.abs(deltaX) > mOneInchInPx / 5) )) {
if (DEBUG_TOUCHES) {
String dbgMsg = "onFling - vX: " + vX + ", vY: " + vY
+ ", e1.X: " + (event1 != null ? event1.getX() : -1) + ", e2.X: " + event2.getX()
+ ", e1.Y: " + (event1 != null ? event1.getY() : -1) + ", e2.Y: " + event2.getY()
+ ", height: " + mParentView.getHeight()
+ ", e1: " + event1 + ", e2: " + event2;
Log.d(TAG, dbgMsg);
Log.d(TAG, " onFling - false, deltaX too small, deltaX: " + deltaX);
}
return false;
}

// sometimes vX from onFling is not reliable
boolean isSwipeLeft = deltaX < 0;
if (DEBUG_TOUCHES) {
Log.d(TAG, " onFling - swipe " + (isSwipeLeft ? "left" : "right")
+ ", vX: " + vX + ", deltaX: " + deltaX + ", deltaY: " + absDeltaY);
}
// The following logs cases that framework-supplied vX is buggy.
if (deltaX < 0 && vX > 0 || deltaX > 0 && vX < 0) {
Log.w(TAG, "onFling: vX and deltaX are not in the same direction. "
+ " deltaX: " + deltaX + " , vX: " + vX);
}

// logic to support horizontal swipes at screen bottom
if (isSwipeLeft) {
onSwipeLeftAtViewBottom();
} else {
onSwipeRightAtViewBottom();
}
return true;
}
});
}

// accept fling on screen / view bottom only
if (mParentView.getHeight() - event2.getY() > mOneInchInPx) {
if (DEBUG_TOUCHES) {
Log.d(TAG, " onFling - false, not on screen bottom");
}
return false;
}

// accept flings with only small vertical delta only
float absDeltaY = Math.abs(event2.getY() - event1.getY());
// Note: relatively large vertical leeway (1 in) is allowed here
// because somehow, truly horizontal swipes often are not processed
// i.e., those horizontal swipes are not passed to the parent OnTouchListener
// at all.
// The swipes that get registered tend to have some leeway.
if (absDeltaY > mOneInchInPx) {
if (DEBUG_TOUCHES) {
Log.d(TAG, " onFling - false, absDeltaY too large, absDeltaY: " + absDeltaY);
}
return false;
}
@Override
public boolean onTouch(View view, MotionEvent event) {
if (DEBUG_TOUCHES) { Log.v(TAG, "onTouch - e: " + event); }
return mDetector.onTouchEvent(event);
}

// accept flings with big enough horizontal delta
float deltaX = event2.getX() - event1.getX();
if (Math.abs(deltaX) < mOneInchInPx / 2) {
if (DEBUG_TOUCHES) {
Log.d(TAG, " onFling - false, deltaX too small, deltaX: " + deltaX);
}
return false;
}
public abstract void onSwipeLeftAtViewBottom();

// sometimes vX from onFling is not reliable
boolean isSwipeLeft = deltaX < 0;
if (DEBUG_TOUCHES) {
Log.d(TAG, " swipe " + (isSwipeLeft ? "left" : "right")
+ ", vX: " + vX + ", deltaX: " + deltaX + ", deltaY: " + absDeltaY);
}
if (deltaX < 0 && vX > 0 || deltaX > 0 && vX < 0) {
Log.w(TAG, "onFling: vX and deltaX are not in the same direction. "
+ " deltaX: " + deltaX + " , vX: " + vX);
}
public abstract void onSwipeRightAtViewBottom();

if (isSwipeLeft) {
onSwipeLeftAtViewBottom();
} else {
onSwipeRightAtViewBottom();
}
return true;
}
});
}
}

/**
* A replacement of {@link GestureDetectorCompat} that fixes the issue
* that in invoking {@link android.view.GestureDetector.OnGestureListener#onFling(MotionEvent, MotionEvent, float, float)}
* call, the supplied parameter <code>event1</code>, the gesture start event, is sometimes missing.
*
* This class fixes the issue: when event1 is null, it supplies an approximation
* (of the first MotionEvent of the gesture that is tracked)
*/
private static class FixedGestureDetectorCompat {
private static final String TAG = "FFR-FGestureD";

@Override
public boolean onTouch(View view, MotionEvent event) {
if (DEBUG_TOUCHES) { Log.v(TAG, "onTouch - e: " + event); }

// tracking the gesture start event,
// to be used by mDetector.onFling() implementation
// where event1 (start of a gesture) is often (unexpectedly) null.
// A cleaner implementation would have the logic built into a
// GestureDetectorCompat subclass.
// However, GestureDetectorCompat is final so it is not possible
private static final boolean DEBUG_TOUCHES = true && BuildConfig.DEBUG;

@NonNull
private final GestureDetectorCompat mDetector;

// to be used by listener's onFling() in case event1 is null, i.e., no down event
private MotionEvent mCurrentStartEvent;

public FixedGestureDetectorCompat(@NonNull Context context,
@NonNull GestureDetector.OnGestureListener listener) {
mDetector = new GestureDetectorCompat(context, new OnGestureListenerDecorator(listener));
}

public boolean isLongpressEnabled() {
return mDetector.isLongpressEnabled();
}

public boolean onTouchEvent(MotionEvent event) {
// tracking the gesture start event,
// to be used by mDetector's listener.onFling() implementation
// where event1 (start of a gesture) is often (unexpectedly) null.
// (somehow in some system, the initial ACTION_DOWN is often missed in flings)
switch (event.getActionMasked()) {
case MotionEvent.ACTION_DOWN:
case MotionEvent.ACTION_MOVE:
if (mCurrentStartEvent == null ||
mCurrentStartEvent.getDownTime() != event.getDownTime()) {
// The downtime test: In some edge cases (reasons not known yet), an
// old (from previous user gesture) event is still kept as mCurrentStartEvent.
// The downtime test ensures an old one (which has a different downtime)
// will be discarded
if (DEBUG_TOUCHES) {
Log.v(TAG, "onTouchEvent - a new start event. type: "
+ event.getActionMasked());
}
mCurrentStartEvent = MotionEvent.obtain(event);
}
}

try {
boolean res = mDetector.onTouchEvent(event);
return res;
} finally {
switch (event.getActionMasked()) {
case MotionEvent.ACTION_DOWN:
case MotionEvent.ACTION_MOVE:
if (mCurrentStartEvent == null ||
mCurrentStartEvent.getDownTime() != event.getDownTime()) {
// The downtime test: In some edge cases (reasons not known yet), an
// old (from previous user gesture) event is still kept as mCurrentStartEvent.
// The downtime test ensures an old one (which has a different downtime)
// will be discarded
mCurrentStartEvent = MotionEvent.obtain(event);
case MotionEvent.ACTION_UP:
case MotionEvent.ACTION_CANCEL:
if (DEBUG_TOUCHES) {
Log.v(TAG, "onTouchEvent - gesture end. release start event: "
+ (mCurrentStartEvent != null));
}
if (mCurrentStartEvent != null) {
mCurrentStartEvent.recycle();
mCurrentStartEvent = null;
}
}
}
}

try {
boolean res = mDetector.onTouchEvent(event);
return res;
} finally {
switch (event.getActionMasked()) {
case MotionEvent.ACTION_UP:
case MotionEvent.ACTION_CANCEL:
if (mCurrentStartEvent != null) {
mCurrentStartEvent.recycle();
mCurrentStartEvent = null;
}
}
}
public void setIsLongpressEnabled(boolean enabled) {
mDetector.setIsLongpressEnabled(enabled);
}

public void setOnDoubleTapListener(GestureDetector.OnDoubleTapListener listener) {
mDetector.setOnDoubleTapListener(listener);
}

/**
* The decorator fixes the null event1 on {@link #onFling(MotionEvent, MotionEvent, float, float)}
* if needed
*/
private class OnGestureListenerDecorator implements GestureDetector.OnGestureListener {
@NonNull
private final GestureDetector.OnGestureListener mListener;

public OnGestureListenerDecorator(@NonNull GestureDetector.OnGestureListener listener) {
mListener = listener;
}

public abstract void onSwipeLeftAtViewBottom();
@Override
public boolean onDown(MotionEvent e) {
return mListener.onDown(e);
}

public abstract void onSwipeRightAtViewBottom();
@Override
public void onShowPress(MotionEvent e) {
mListener.onShowPress(e);
}

@Override
public boolean onSingleTapUp(MotionEvent e) {
return mListener.onSingleTapUp(e);
}

@Override
public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
// LATER: probably I need to wrap around onScroll similar to onFling
return mListener.onScroll(e1, e2, distanceX, distanceY);
}

@Override
public void onLongPress(MotionEvent e) {
mListener.onLongPress(e);
}

@Override
public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
// somehow event1 (start of a fling) is often null (i.e., no ACTION_DOWN)
// use the first action move as an approximation
MotionEvent evStart = e1!= null ? e1 : mCurrentStartEvent;

if (evStart == null) {
Log.w(TAG, "onFling - aborted. Cannot determine Start Event.");
return false;
}
if (e2.getDownTime() != evStart.getDownTime()) {
if (e1 != null) {
// case evStart comes from original GestureDetectorCompat, which
// supplies a buggy one from an old gesture. Use our approximation.
// Example scenarios:
// 1. framework only occasionally detects ACTION_DOWN (the proper gesture start).
// at least on the tested devices.
// 2. when it does detect ACTION_DOWN, it first uses it correctly.
// 3. however, for subsequent gestures (with no ACTION_DOWN), framework continues
// to use the old ACTION_DOWN in step 2, and passes it to here.
//
// See relevant codes:
// - in GestureDetectorCompat.java:307-310 (support v25.4.0) the only place
// member mCurrentDownEvent ever get set (in dealing with ACTION_DOWN)
// - when subsequent gestures (with no ACTION_DOWN) happen, mCurrentDownEvent
// thus retains the old value.
if (DEBUG_TOUCHES) {
Log.d(TAG, "onFling - framework-supplied Start Event e1 comes from an old gesture with downTime ["
+ e1.getDownTime() + "]. Use our approximation.");
}
evStart = mCurrentStartEvent;
} else {
// a case that should not happen, our own approximation event
// somehow comes from a different (old) gesture
Log.e(TAG, "onFling - aborted. Cannot find a proper Start Event. Our approximation"
+ " comes from an old gesture. evStart: " + evStart + ", e2: " + e2);
return false;
}
}

return mListener.onFling(evStart, e2, velocityX, velocityY);
}
}
}

}

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