HorizontalPager changes

AndroidManifest.xml

@@ -26,5 +26,8 @@
         <activity
             android:name=".HorizontalPagerDemo"
             android:label="@string/app_name" />
+        <activity
+            android:name=".ListHorizontalPagerDemo"
+            android:label="@string/app_name" />
     </application>
 </manifest>

res/layout/activity_list_horizontal_pager_demo.xml

@@ -0,0 +1,29 @@
+<?xml version="1.0" encoding="utf-8"?>
+<com.github.ysamlan.horizontalpager.HorizontalPager
+	xmlns:android="http://schemas.android.com/apk/res/android"
+	android:id="@id/horizontal_pager"
+	android:layout_width="fill_parent"
+	android:layout_height="fill_parent">
+
+	<ListView
+		android:id="@+id/list1"
+		android:layout_width="fill_parent"
+		android:layout_height="fill_parent"
+		android:cacheColorHint="#ff440000"
+		android:background="#ff440000" />
+
+	<ListView
+		android:id="@+id/list2"
+		android:layout_width="fill_parent"
+		android:layout_height="fill_parent"
+		android:cacheColorHint="#ff004400"
+		android:background="#ff004400" />
+
+	<ListView
+		android:id="@+id/list3"
+		android:layout_width="fill_parent"
+		android:layout_height="fill_parent"
+		android:cacheColorHint="#ff000044"
+		android:background="#ff000044" />
+
+</com.github.ysamlan.horizontalpager.HorizontalPager>

res/layout/activity_tabbed_horizontal_pager_demo.xml

@@ -30,7 +30,7 @@
             android:text="#3" />
     </RadioGroup>
     <com.github.ysamlan.horizontalpager.HorizontalPager
-        android:id="@+id/horizontal_pager"
+        android:id="@id/horizontal_pager"
         android:layout_width="fill_parent"
         android:layout_height="0px"
         android:layout_weight="1">
@@ -71,9 +71,20 @@
                 android:background="#00f" />
         </ScrollView>
     </com.github.ysamlan.horizontalpager.HorizontalPager>
-    <Button
-        android:id="@+id/simple_demo_btn"
-        android:layout_height="wrap_content"
-        android:layout_width="fill_parent"
-        android:text="Simple Demo" />
+    <LinearLayout
+    	android:layout_height="wrap_content"
+    	android:layout_width="fill_parent">
+	    <Button
+	        android:id="@+id/simple_demo_btn"
+	        android:layout_height="wrap_content"
+	        android:layout_width="0dp"
+	        android:layout_weight="1"
+	        android:text="Simple Demo" />
+	    <Button
+	        android:id="@+id/list_demo_btn"
+	        android:layout_height="wrap_content"
+	        android:layout_width="0dp"
+	        android:layout_weight="1"
+	        android:text="List Demo" />
+   	</LinearLayout>
 </LinearLayout>

res/values/ids.xml

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <item type="id" name="horizontal_pager" />
+</resources>

src/com/github/ysamlan/horizontalpager/HorizontalPager.java

@@ -21,6 +21,8 @@
 package com.github.ysamlan.horizontalpager;
 
 import android.content.Context;
+import android.os.Parcel;
+import android.os.Parcelable;
 import android.util.AttributeSet;
 import android.util.DisplayMetrics;
 import android.view.Display;
@@ -30,6 +32,8 @@
 import android.view.ViewConfiguration;
 import android.view.ViewGroup;
 import android.view.WindowManager;
+import android.view.animation.DecelerateInterpolator;
+import android.view.animation.Interpolator;
 import android.widget.Scroller;
 
 /**
@@ -70,6 +74,7 @@ public final class HorizontalPager extends ViewGroup {
     private static final int SNAP_VELOCITY_DIP_PER_SECOND = 600;
     // Argument to getVelocity for units to give pixels per second (1 = pixels per millisecond).
     private static final int VELOCITY_UNIT_PIXELS_PER_SECOND = 1000;
+    private static final float INTERPOLATION_FACTOR = 1.75f;
 
     private static final int TOUCH_STATE_REST = 0;
     private static final int TOUCH_STATE_HORIZONTAL_SCROLLING = 1;
@@ -124,7 +129,9 @@ public HorizontalPager(final Context context, final AttributeSet attrs) {
      * Sets up the scroller and touch/fling sensitivity parameters for the pager.
      */
     private void init() {
-        mScroller = new Scroller(getContext());
+        // use a DecelerateInterpolator to have more natural movement on long horizontal scrolls
+        Interpolator interpolator = new DecelerateInterpolator(INTERPOLATION_FACTOR);
+        mScroller = new Scroller(getContext(), interpolator);
 
         // Calculate the density-dependent snap velocity in pixels
         DisplayMetrics displayMetrics = new DisplayMetrics();
@@ -138,6 +145,22 @@ private void init() {
         mMaximumVelocity = configuration.getScaledMaximumFlingVelocity();
     }
 
+    @Override
+    protected Parcelable onSaveInstanceState() {
+        final SavedState state = new SavedState(super.onSaveInstanceState());
+        state.mCurrentScreen = mCurrentScreen;
+        return state;
+    }
+
+    @Override
+    protected void onRestoreInstanceState(Parcelable state) {
+        SavedState savedState = (SavedState) state;
+        super.onRestoreInstanceState(savedState.getSuperState());
+        if (savedState.mCurrentScreen != -1) {
+            mCurrentScreen = savedState.mCurrentScreen;
+        }
+    }
+
     @Override
     protected void onMeasure(final int widthMeasureSpec, final int heightMeasureSpec) {
         super.onMeasure(widthMeasureSpec, heightMeasureSpec);
@@ -162,9 +185,7 @@ protected void onMeasure(final int widthMeasureSpec, final int heightMeasureSpec
         if (mFirstLayout) {
             scrollTo(mCurrentScreen * width, 0);
             mFirstLayout = false;
-        }
-
-        else if (width != mLastSeenLayoutWidth) { // Width has changed
+        } else if (width != mLastSeenLayoutWidth) { // Width has changed
             /*
              * Recalculate the width and scroll to the right position to be sure we're in the right
              * place in the event that we had a rotation that didn't result in an activity restart
@@ -203,77 +224,39 @@ protected void onLayout(final boolean changed, final int l, final int t, final i
 
     @Override
     public boolean onInterceptTouchEvent(final MotionEvent ev) {
-        /*
-         * By Yoni Samlan: Modified onInterceptTouchEvent based on standard ScrollView's
-         * onIntercept. The logic is designed to support a nested vertically scrolling view inside
-         * this one; once a scroll registers for X-wise scrolling, handle it in this view and don't
-         * let the children, but once a scroll registers for y-wise scrolling, let the children
-         * handle it exclusively.
-         */
         final int action = ev.getAction();
         boolean intercept = false;
 
         switch (action) {
             case MotionEvent.ACTION_MOVE:
-                /*
-                 * If we're in a horizontal scroll event, take it (intercept further events). But if
-                 * we're mid-vertical-scroll, don't even try; let the children deal with it. If we
-                 * haven't found a scroll event yet, check for one.
-                 */
-                if (mTouchState == TOUCH_STATE_HORIZONTAL_SCROLLING) {
-                    /*
-                     * We've already started a horizontal scroll; set intercept to true so we can
-                     * take the remainder of all touch events in onTouchEvent.
-                     */
-                    intercept = true;
-                } else if (mTouchState == TOUCH_STATE_VERTICAL_SCROLLING) {
-                    // Let children handle the events for the duration of the scroll event.
-                    intercept = false;
-                } else { // We haven't picked up a scroll event yet; check for one.
-
-                    /*
-                     * If we detected a horizontal scroll event, start stealing touch events (mark
-                     * as scrolling). Otherwise, see if we had a vertical scroll event -- if so, let
-                     * the children handle it and don't look to intercept again until the motion is
-                     * done.
-                     */
-
-                    final float x = ev.getX();
-                    final int xDiff = (int) Math.abs(x - mLastMotionX);
-                    boolean xMoved = xDiff > mTouchSlop;
-
-                    if (xMoved) {
-                        // Scroll if the user moved far enough along the X axis
-                        mTouchState = TOUCH_STATE_HORIZONTAL_SCROLLING;
-                        mLastMotionX = x;
-                    }
-
-                    final float y = ev.getY();
-                    final int yDiff = (int) Math.abs(y - mLastMotionY);
-                    boolean yMoved = yDiff > mTouchSlop;
+                final int xDiff = (int) Math.abs(ev.getX() - mLastMotionX);
+                if (xDiff > mTouchSlop) {
+                    mTouchState = TOUCH_STATE_HORIZONTAL_SCROLLING;
+                    mLastMotionX = ev.getX();
+                }
 
-                    if (yMoved) {
-                        mTouchState = TOUCH_STATE_VERTICAL_SCROLLING;
-                    }
+                final int yDiff = (int) Math.abs(ev.getY() - mLastMotionY);
+                if (yDiff > mTouchSlop) {
+                    mTouchState = TOUCH_STATE_VERTICAL_SCROLLING;
                 }
 
+                if ((Math.abs(xDiff * 2) > Math.abs(yDiff)) && (xDiff > mTouchSlop)) {
+                    intercept = true;
+                }
                 break;
-            case MotionEvent.ACTION_CANCEL:
+
             case MotionEvent.ACTION_UP:
-                // Release the drag.
                 mTouchState = TOUCH_STATE_REST;
                 break;
+
             case MotionEvent.ACTION_DOWN:
-                /*
-                 * No motion yet, but register the coordinates so we can check for intercept at the
-                 * next MOVE event.
-                 */
                 mLastMotionY = ev.getY();
                 mLastMotionX = ev.getX();
                 break;
+
             default:
                 break;
-            }
+        }
 
         return intercept;
     }
@@ -501,4 +484,38 @@ public static interface OnScreenSwitchListener {
          */
         void onScreenSwitched(int screen);
     }
+
+    /**
+     * A parcelable so we can save our current screen and return to it after an activity destroy.
+     */
+    public static class SavedState extends BaseSavedState {
+
+        private int mCurrentScreen = -1;
+
+        public SavedState(Parcelable superState) {
+            super(superState);
+        }
+
+        public SavedState(Parcel in) {
+            super(in);
+            mCurrentScreen = in.readInt();
+        }
+
+        @Override
+        public void writeToParcel(Parcel out, int flags) {
+            super.writeToParcel(out, flags);
+            out.writeInt(mCurrentScreen);
+        }
+
+        public static final Parcelable.Creator<SavedState> CREATOR = new Parcelable.Creator<SavedState>() {
+            public SavedState createFromParcel(Parcel in) {
+                return new SavedState(in);
+            }
+
+            public SavedState[] newArray(int size) {
+                return new SavedState[size];
+            }
+        };
+    }
+
 }

src/com/github/ysamlan/horizontalpager/HorizontalPagerDemo.java

@@ -20,6 +20,7 @@ public void onCreate(final Bundle savedInstanceState) {
 
         // Create the view switcher
         HorizontalPager realViewSwitcher = new HorizontalPager(getApplicationContext());
+        realViewSwitcher.setId(R.id.horizontal_pager);
 
         // Add some views to it
         final int[] backgroundColors =

src/com/github/ysamlan/horizontalpager/ListHorizontalPagerDemo.java

@@ -0,0 +1,65 @@
+package com.github.ysamlan.horizontalpager;
+
+import java.util.Random;
+
+import android.app.Activity;
+import android.os.Bundle;
+import android.widget.ArrayAdapter;
+import android.widget.ListAdapter;
+import android.widget.ListView;
+
+/**
+ * An example of a HorizontalPager used to display a few ListViews side by side.
+ *
+ * @author Gil Shapira
+ */
+public class ListHorizontalPagerDemo extends Activity {
+
+    private static final int LIST_SIZE = 50;
+
+    @Override
+    public void onCreate(final Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+        setContentView(R.layout.activity_list_horizontal_pager_demo);
+
+        // set an adapter in each of the ListViews defined in the XML
+        ListView list1 = (ListView) findViewById(R.id.list1);
+        ListView list2 = (ListView) findViewById(R.id.list2);
+        ListView list3 = (ListView) findViewById(R.id.list3);
+        list1.setAdapter(generateAdapter());
+        list2.setAdapter(generateAdapter());
+        list3.setAdapter(generateAdapter());
+    }
+
+    /**
+     * @return an adapter that serves random strings in TextViews.
+     */
+    private ListAdapter generateAdapter() {
+        String[] strings = generateStrings();
+        ListAdapter adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, strings);
+        return adapter;
+    }
+
+    /**
+     * @return an array full of random lorem ipsum words.
+     */
+    private String[] generateStrings() {
+        // make a collection of words from the lorem ipsum text
+        if (sWords == null) {
+            sWords = getString(R.string.lipsum).split(" ");
+        }
+
+        Random rand = new Random();
+        String[] strings = new String[LIST_SIZE];
+        for (int i = 0; i < LIST_SIZE; i++) {
+            // pick a random word from the array
+            int w = rand.nextInt(sWords.length);
+            strings[i] = sWords[w];
+        }
+
+        return strings;
+    }
+
+    private static String[] sWords = null;
+
+}

src/com/github/ysamlan/horizontalpager/TabbedHorizontalPagerDemo.java

@@ -19,9 +19,7 @@ public void onCreate(final Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_tabbed_horizontal_pager_demo);
         mPager = (HorizontalPager) findViewById(R.id.horizontal_pager);
-        mPager.setOnScreenSwitchListener(onScreenSwitchListener);
         mRadioGroup = (RadioGroup) findViewById(R.id.tabs);
-        mRadioGroup.setOnCheckedChangeListener(onCheckedChangedListener);
 
         // Go to the simple demo if the user clicks on the simple demo button
         findViewById(R.id.simple_demo_btn).setOnClickListener(new View.OnClickListener() {
@@ -31,6 +29,22 @@ public void onClick(final View v) {
                         HorizontalPagerDemo.class));
             }
         });
+
+        // Go to the list demo if the user clicks on the list demo button
+        findViewById(R.id.list_demo_btn).setOnClickListener(new View.OnClickListener() {
+            @Override
+            public void onClick(final View v) {
+                startActivity(new Intent(TabbedHorizontalPagerDemo.this,
+                        ListHorizontalPagerDemo.class));
+            }
+        });
+    }
+
+    @Override
+    protected void onResume() {
+        super.onResume();
+        mPager.setOnScreenSwitchListener(onScreenSwitchListener);
+        mRadioGroup.setOnCheckedChangeListener(onCheckedChangedListener);
     }
 
     private final HorizontalPager.OnScreenSwitchListener onScreenSwitchListener =