feat: Implement a page-wise scroll for BaseListView.

android/src/org/coolreader/crengine/BaseActivity.java

@@ -1323,6 +1323,8 @@ public void applyAppSetting(String key, String value) {
 			setScreenBacklightDuration(Utils.parseInt(value, 0));
 		} else if (key.equals(PROP_NIGHT_MODE)) {
 			setNightMode(flg);
+		} else if (key.equals(PROP_APP_PAGEWISE_SCROLL)) {
+			DeviceInfo.PAGEWISE_SCROLLING = flg;
 		} else if (key.equals(PROP_APP_SCREEN_UPDATE_MODE)) {
 			setScreenUpdateMode(EinkScreen.EinkUpdateMode.byCode(Utils.parseInt(value, 0)), getContentView());
 		} else if (key.equals(PROP_APP_SCREEN_UPDATE_INTERVAL)) {
@@ -1957,6 +1959,7 @@ public Properties loadSettings(BaseActivity activity, File file) {
 			props.applyDefault(ReaderView.PROP_APP_SHOW_COVERPAGES, "1");
 			props.applyDefault(ReaderView.PROP_APP_COVERPAGE_SIZE, "1");
 			props.applyDefault(ReaderView.PROP_APP_SCREEN_ORIENTATION, "0"); // "0"
+			props.applyDefault(ReaderView.PROP_APP_PAGEWISE_SCROLL, "0");
 			props.applyDefault(ReaderView.PROP_CONTROLS_ENABLE_VOLUME_KEYS, "1");
 			props.applyDefault(ReaderView.PROP_APP_TAP_ZONE_HILIGHT, "0");
 			props.applyDefault(ReaderView.PROP_APP_BOOK_SORT_ORDER, FileInfo.DEF_SORT_ORDER.name());

android/src/org/coolreader/crengine/BaseListView.java

@@ -23,17 +23,93 @@
 
 import android.content.Context;
 import android.graphics.Rect;
+import android.util.DisplayMetrics;
 import android.view.KeyEvent;
+import android.view.MotionEvent;
 import android.view.View;
 import android.widget.ListView;
 
 public class BaseListView  extends ListView {
-	public BaseListView(Context context, boolean fastScrollEnabled) {
-		super(context);
+
+    //The Values were originally tested on a 440dpi screen, hence the conversion factor in the constructor
+    private float SWIPE_THRESHOLD_PX = 100f;
+
+    private float NO_MOVE_THRESHOLD_PX = 5f;
+
+    private float touchStartY = 0f;
+
+
+    public BaseListView(Context context, boolean fastScrollEnabled) {
+        super(context);
         setFocusable(true);
         setFocusableInTouchMode(true);
         setFastScrollEnabled(fastScrollEnabled);
-	}
+        DisplayMetrics displayMetrics = getResources().getDisplayMetrics();
+        //The Values were originally tested on a 440dpi screen, hence the conversion factor
+        final float dpiDependentFactor = displayMetrics.ydpi / 440;
+        SWIPE_THRESHOLD_PX = Math.round(dpiDependentFactor * SWIPE_THRESHOLD_PX);
+        NO_MOVE_THRESHOLD_PX = Math.round(dpiDependentFactor * NO_MOVE_THRESHOLD_PX);
+    }
+
+    /** This method is designed to allow the ListView to scroll page-wise.
+     *  FileBrowser.MyGestureListener or any other listener should not be impaired by this.
+     * */
+
+    @Override
+    public boolean onTouchEvent(MotionEvent ev) {
+            boolean returnValue = false;
+
+        if (DeviceInfo.PAGEWISE_SCROLLING) {
+            switch (ev.getAction()) {
+                //Start registering the events.
+                //Allow ACTION_DOWN to be passed normally to the ListView
+                //to keep the click/longclick functionality
+                case MotionEvent.ACTION_DOWN:
+                    touchStartY = ev.getY();
+                    returnValue = super.onTouchEvent(ev);
+                    break;
+
+                case MotionEvent.ACTION_MOVE:
+                    /**
+                     * Interrupt normal scrolling, when NO_MOVE_THRESHOLD_PX is reached.
+                     * Once the movement starts, claim the following events.
+                     * NO_MOVE_THRESHOLD_PX is there to allow for some little movement when
+                     * performing a click.
+                     */
+
+                    //TODO: NO_MOVE_THRESHOLD_PX may need some testing and fine tuning
+                    returnValue = true;
+                    if (Math.abs(touchStartY - ev.getY()) >= NO_MOVE_THRESHOLD_PX) {
+                        ev.setAction(MotionEvent.ACTION_CANCEL);
+                    }
+
+                    super.onTouchEvent(ev);
+                    break;
+
+                case MotionEvent.ACTION_UP:
+                case MotionEvent.ACTION_CANCEL:
+                    /**
+                     * Scroll page-wise when SWIPE_THRESHOLD_PX is reached.
+                     */
+                    //TODO maybe tweak SWIPE_THRESHOLD_PX too, current values are rather experimental
+                    super.onTouchEvent(ev);
+
+                    if (Math.abs(touchStartY - ev.getY()) >= SWIPE_THRESHOLD_PX) {  //delta is positive = swiped up (next page)
+                        if (touchStartY - ev.getY() > 0) {
+                            scrollPage(1);
+                        } else {
+                            scrollPage(-1);
+                        }
+                        returnValue = true;
+                    }
+                    break;
+            }
+        } else {
+            returnValue = super.onTouchEvent(ev);
+        }
+        return returnValue;
+    }
+
 
 	@Override
     public boolean onKeyDown(int keyCode, KeyEvent event) {
@@ -46,36 +122,75 @@ public boolean onKeyDown(int keyCode, KeyEvent event) {
         else if (keyCode == ReaderView.SONY_DPAD_LEFT_SCANCODE || keyCode == ReaderView.SONY_DPAD_UP_SCANCODE || keyCode==KeyEvent.KEYCODE_DPAD_UP || keyCode == KeyEvent.KEYCODE_DPAD_LEFT )
             dir = -1;
         //} else {
-        else if (keyCode == KeyEvent.KEYCODE_8 || keyCode == ReaderView.NOOK_KEY_NEXT_RIGHT || keyCode == KeyEvent.KEYCODE_DPAD_RIGHT || keyCode == ReaderView.NOOK_KEY_SHIFT_DOWN)
+        else if (keyCode == KeyEvent.KEYCODE_8 || keyCode == ReaderView.NOOK_KEY_NEXT_RIGHT || keyCode == KeyEvent.KEYCODE_DPAD_RIGHT || keyCode == ReaderView.NOOK_KEY_SHIFT_DOWN || keyCode == KeyEvent.KEYCODE_PAGE_DOWN)
             dir = 1;
-        else if (keyCode == KeyEvent.KEYCODE_2 || keyCode == ReaderView.NOOK_KEY_PREV_RIGHT || keyCode == KeyEvent.KEYCODE_DPAD_LEFT || keyCode == ReaderView.NOOK_KEY_SHIFT_UP)
+        else if (keyCode == KeyEvent.KEYCODE_2 || keyCode == ReaderView.NOOK_KEY_PREV_RIGHT || keyCode == KeyEvent.KEYCODE_DPAD_LEFT || keyCode == ReaderView.NOOK_KEY_SHIFT_UP || keyCode == KeyEvent.KEYCODE_PAGE_UP)
             dir = -1;
         //}
-        if (dir != 0) {            
-            int firstPos = getFirstVisiblePosition();
-            int lastPos  = getLastVisiblePosition();
-            int count    = getCount();
-
-            int delta = 1;
-            if( dir < 0 ) {
-                View v = getChildAt(0);
-                if( v != null ) {
-                    int fh = v.getHeight();
-                    Rect r = new Rect(0,0,v.getWidth(),fh);
-                    getChildVisibleRect(v, r, null);
-                    delta = (r.height() < fh) ? 1 : 0;
-                }
-            }
-
-            int nextPos = ( dir > 0 ) ? Math.min(lastPos + 1, count - 1) : Math.max(0, firstPos - (lastPos - firstPos) + delta);
-
-            // Log.w("CoolReader", "first =" + firstPos + " last = " + lastPos + " next = " + nextPos + " count = " + count);
-
-            setSelection(nextPos);  
-            clearFocus();
-
+        if (dir != 0) {
+            scrollPage(dir);
             return true;
         }
         return super.onKeyDown(keyCode, event);
     }
+
+    /** Scroll the ListView page-wise.
+     * Logic is:
+     * 1. Scrolling down - the last (bottom) not fully visible view should be the first
+     *      fully displayed view on the next page.
+     * 2. Scrolling up - the first (top) not fully visible view should be the last
+     *      fully displayed view on the previous page
+     * */
+    private void scrollPage(int dir) {
+        int firstPos = getFirstVisiblePosition();
+        int lastPos  = getLastVisiblePosition();
+        int count    = getCount();
+
+        int delta = 0;
+        int newTopItem = 0;
+        if( dir < 0 ) {
+            //Check if the currently displayed top childview is fully visible or incomplete
+            View v = getChildAt(0);
+            if( v != null ) {
+                int fh = v.getHeight();
+                Rect r = new Rect(0,0,v.getWidth(),fh);
+                getChildVisibleRect(v, r, null);
+                delta = (r.height() < fh) ? 1 : 0;
+            }
+
+            //Scrolling up, account for when the items can have different heights
+            // (e.g. by using a larger font, breaking into more lines, etc.)
+            newTopItem = Math.max(0, firstPos - 1 + delta);
+            Rect visibleListViewRect = new Rect();
+            this.getGlobalVisibleRect(visibleListViewRect);
+            int visibleHeight = visibleListViewRect.height();
+            int usableHeight = 0;
+            for (int i = newTopItem; i >= 0;  i--) {
+                //getchildAt() returns null if the item is not visible.
+                //Ask adapter directly to get the children parameters
+                View view = getAdapter().getView(i, null, this);
+                /**
+                 * Because normally ListViews are measured lazy, view.getMeasuredHeight() can return 0
+                 * when the view hasn't gone through a layout pass yet.
+                 * Inflate and measure each item view, forcing a layout pass.
+                 * MeasureSpec.UNSPECIFIED for height lets the view report its natural height,
+                 * and MeasureSpec.EXACTLY for width constrains it to the real ListView width
+                 * so it wraps correctly.
+                 */
+                view.measure( View.MeasureSpec.makeMeasureSpec(this.getWidth(), MeasureSpec.EXACTLY),
+                              View.MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED));
+                usableHeight += view.getMeasuredHeight() + getDividerHeight();
+                if (usableHeight > visibleHeight) {
+                    //use last view that fits fully into the next page as top view
+                    break;
+                }
+                newTopItem = i;
+            }
+        }
+
+        int nextPos = ( dir > 0 ) ? Math.min(lastPos, count - 1) : Math.max(0, newTopItem) ;
+
+        setSelection(nextPos);
+        clearFocus();
+    }
 }

android/src/org/coolreader/crengine/DeviceInfo.java

@@ -76,6 +76,8 @@ public class DeviceInfo {
 	public final static Integer DEF_FONT_SIZE;
 	public final static boolean ONE_COLUMN_IN_LANDSCAPE;
 
+	public static boolean PAGEWISE_SCROLLING = false;
+
 	// minimal screen backlight level percent for different devices
 	private static final String[] MIN_SCREEN_BRIGHTNESS_DB = {
 		"LGE;LG-P500",       "6", // LG Optimus One

android/src/org/coolreader/crengine/OptionsDialog.java

@@ -2905,6 +2905,10 @@ private void setupReaderOptions()
 		mBounceProtectionOption = new ListOption(this, getString(R.string.options_controls_bonce_protection), PROP_APP_BOUNCE_TAP_INTERVAL).add(mBounceProtectionValues, mBounceProtectionTitles).setDefaultValue(String.valueOf(150));
 		mOptionsControls.add(mBounceProtectionOption);
 		doubleTapOnChange.run();
+		Runnable changehandlerPagewiseScroll = () -> {
+			DeviceInfo.PAGEWISE_SCROLLING = mProperties.getBool(PROP_APP_PAGEWISE_SCROLL, false);
+		};
+		mOptionsControls.add(new BoolOption(this, "Page-wise scroll", PROP_APP_PAGEWISE_SCROLL).setDefaultValue("0").setOnChangeHandler(changehandlerPagewiseScroll));
 		if ( !DeviceInfo.EINK_SCREEN )
 			mOptionsControls.add(new BoolOption(this, getString(R.string.options_controls_enable_volume_keys), PROP_CONTROLS_ENABLE_VOLUME_KEYS).setDefaultValue("1"));
 		mOptionsControls.add(new BoolOption(this, getString(R.string.options_app_tapzone_hilite), PROP_APP_TAP_ZONE_HILIGHT).setDefaultValue("0").setIconIdByAttr(R.attr.cr3_option_touch_drawable, R.drawable.cr3_option_touch));

android/src/org/coolreader/crengine/ReaderView.java

@@ -2874,6 +2874,7 @@ public boolean showManual() {
 	}
 
 	private boolean hiliteTapZoneOnTap = false;
+	private boolean enablePagewiseScroll = false;
 	private boolean enableVolumeKeys = true;
 	static private final int DEF_PAGE_FLIP_MS = 300;
 
@@ -2907,6 +2908,8 @@ public void applyAppSetting(String key, String value) {
 			pageFlipAnimationSpeedMs = pageFlipAnimationMode != PAGE_ANIMATION_NONE ? DEF_PAGE_FLIP_MS : 0;
 		} else if (PROP_CONTROLS_ENABLE_VOLUME_KEYS.equals(key)) {
 			enableVolumeKeys = flg;
+		} else if (PROP_APP_PAGEWISE_SCROLL.equals(key)) {
+			enablePagewiseScroll = flg;
 		} else if (PROP_APP_SELECTION_ACTION.equals(key)) {
 			mSelectionAction = Utils.parseInt(value, SELECTION_ACTION_TOOLBAR);
 		} else if (PROP_APP_MULTI_SELECTION_ACTION.equals(key)) {
@@ -2948,6 +2951,7 @@ public void setAppSettings(Properties newSettings, Properties oldSettings) {
 					|| PROP_APP_SCREEN_BACKLIGHT_LOCK.equals(key)
 					|| PROP_APP_TAP_ZONE_HILIGHT.equals(key)
 					|| PROP_APP_DICTIONARY.equals(key)
+					|| PROP_APP_PAGEWISE_SCROLL.equals(key)
 					|| PROP_APP_DOUBLE_TAP_SELECTION.equals(key)
 					|| PROP_APP_BOUNCE_TAP_INTERVAL.equals(key)
 					|| PROP_APP_FLICK_BACKLIGHT_CONTROL.equals(key)

android/src/org/coolreader/crengine/Settings.java

@@ -151,6 +151,7 @@ public interface Settings {
     public static final String PROP_APP_SCREEN_BACKLIGHT_DAY   ="app.screen.backlight.day";
     public static final String PROP_APP_SCREEN_BACKLIGHT_NIGHT ="app.screen.backlight.night";
     public static final String PROP_APP_DOUBLE_TAP_SELECTION     ="app.controls.doubletap.selection";
+	public static final String PROP_APP_PAGEWISE_SCROLL = "app.controls.pagewise.scroll";
     public static final String PROP_APP_BOUNCE_TAP_INTERVAL   ="app.controls.bounce.interval";
     public static final String PROP_APP_TAP_ZONE_ACTIONS_TAP     ="app.tapzone.action.tap";
     public static final String PROP_APP_KEY_ACTIONS_PRESS     ="app.key.action.press";