Merge pull request pakerfeldt#64 from chripo/chripo/lazyinit

lazyinit

Author: pakerfeldt

README.md

@@ -40,6 +40,17 @@ If you need to listen to screen change events you would want to implement your o
         }
     });
 
+### Listen on initialize view events
+
+If you need a lazy View initialization you would want to implement your own `ViewFlow.ViewLazyInitializeListener` and pass it to the `setOnViewLazyInitializeListener()` method.
+
+    viewFlow.setOnViewLazyInitializeListener(new ViewLazyInitializeListener() {
+        public void onViewLazyInitialize(View view, int position) {
+            // Your code here e.g.
+            ((MyAdapter)((AbsListView)view).getAdapter()).initializeData();
+        }
+    });
+
 ### Flow Indicator
 It is also possible to add a flow view indicator to your layout. The purpose of a `FlowIndicator` is to present a visual representation of where in the item list focus is at. You may either implement a `FlowIndicator` yourself or use an implementation provided by the View Flow library. The View Flow library currently supports the following indicators:
 

viewflow/src/org/taptwo/android/widget/ViewFlow.java

@@ -15,7 +15,7 @@
  */
 package org.taptwo.android.widget;
 
-import java.util.ArrayList;
+import java.util.EnumSet;
 import java.util.LinkedList;
 
 import org.taptwo.android.widget.viewflow.R;
@@ -67,6 +67,8 @@ public class ViewFlow extends AdapterView<Adapter> {
 	private int mNextScreen = INVALID_SCREEN;
 	private boolean mFirstLayout = true;
 	private ViewSwitchListener mViewSwitchListener;
+	private ViewLazyInitializeListener mViewInitializeListener;
+	private EnumSet<LazyInit> mLazyInit = EnumSet.allOf(LazyInit.class);
 	private Adapter mAdapter;
 	private int mLastScrollDirection;
 	private AdapterDataSetObserver mDataSetObserver;
@@ -100,6 +102,14 @@ public static interface ViewSwitchListener {
 
 	}
 
+	public static interface ViewLazyInitializeListener {
+		void onViewLazyInitialize(View view, int position);
+	}
+
+	enum LazyInit {
+		LEFT, RIGHT
+	}
+
 	public ViewFlow(Context context) {
 		super(context);
 		mSideBuffer = 3;
@@ -218,18 +228,21 @@ public boolean onInterceptTouchEvent(MotionEvent ev) {
 			break;
 
 		case MotionEvent.ACTION_MOVE:
-			final int xDiff = (int) Math.abs(x - mLastMotionX);
+			final int deltaX = (int) (mLastMotionX - x);
 
-			boolean xMoved = xDiff > mTouchSlop;
+			boolean xMoved = Math.abs(deltaX) > mTouchSlop;
 
 			if (xMoved) {
 				// Scroll if the user moved far enough along the X axis
 				mTouchState = TOUCH_STATE_SCROLLING;
+
+				if (mViewInitializeListener != null)
+					initializeView(deltaX);
 			}
 
 			if (mTouchState == TOUCH_STATE_SCROLLING) {
 				// Scroll to follow the motion event
-				final int deltaX = (int) (mLastMotionX - x);
+
 				mLastMotionX = x;
 
 				final int scrollX = getScrollX();
@@ -313,18 +326,21 @@ public boolean onTouchEvent(MotionEvent ev) {
 			break;
 
 		case MotionEvent.ACTION_MOVE:
-			final int xDiff = (int) Math.abs(x - mLastMotionX);
+			final int deltaX = (int) (mLastMotionX - x);
 
-			boolean xMoved = xDiff > mTouchSlop;
+			boolean xMoved = Math.abs(deltaX) > mTouchSlop;
 
 			if (xMoved) {
 				// Scroll if the user moved far enough along the X axis
 				mTouchState = TOUCH_STATE_SCROLLING;
+
+				if (mViewInitializeListener != null)
+					initializeView(deltaX);
 			}
 
 			if (mTouchState == TOUCH_STATE_SCROLLING) {
 				// Scroll to follow the motion event
-				final int deltaX = (int) (mLastMotionX - x);
+
 				mLastMotionX = x;
 
 				final int scrollX = getScrollX();
@@ -377,6 +393,22 @@ && mCurrentScreen < getChildCount() - 1) {
 		return true;
 	}
 
+	private void initializeView(final float direction) {
+		if (direction > 0) {
+			if (mLazyInit.contains(LazyInit.RIGHT)) {
+				mLazyInit.remove(LazyInit.RIGHT);
+				if (mCurrentBufferIndex+1 < mLoadedViews.size())
+					mViewInitializeListener.onViewLazyInitialize(mLoadedViews.get(mCurrentBufferIndex + 1), mCurrentAdapterIndex + 1);
+			}
+		} else {
+			if (mLazyInit.contains(LazyInit.LEFT)) {
+				mLazyInit.remove(LazyInit.LEFT);
+				if (mCurrentBufferIndex > 0)
+					mViewInitializeListener.onViewLazyInitialize(mLoadedViews.get(mCurrentBufferIndex - 1), mCurrentAdapterIndex - 1);
+			}
+		}
+	}
+
 	@Override
 	protected void onScrollChanged(int h, int v, int oldh, int oldv) {
 		super.onScrollChanged(h, v, oldh, oldv);
@@ -459,6 +491,10 @@ public void setOnViewSwitchListener(ViewSwitchListener l) {
 		mViewSwitchListener = l;
 	}
 
+	public void setOnViewLazyInitializeListener(ViewLazyInitializeListener l) {
+		mViewInitializeListener = l;
+	}
+
 	@Override
 	public Adapter getAdapter() {
 		return mAdapter;
@@ -538,7 +574,10 @@ public void setSelection(int position) {
 
 		View currentView = makeAndAddView(position, true);
 		mLoadedViews.addLast(currentView);
-		
+
+		if (mViewInitializeListener != null)
+			mViewInitializeListener.onViewLazyInitialize(currentView, position);
+
 		for(int offset = 1; mSideBuffer - offset >= 0; offset++) {
 			int leftIndex = position - offset;
 			int rightIndex = position + offset;
@@ -554,27 +593,28 @@ public void setSelection(int position) {
 		requestLayout();
 		setVisibleView(mCurrentBufferIndex, false);
 		if (mIndicator != null) {
-			mIndicator.onSwitched(mLoadedViews.get(mCurrentBufferIndex),
-					mCurrentAdapterIndex);
+			mIndicator.onSwitched(currentView, mCurrentAdapterIndex);
 		}
 		if (mViewSwitchListener != null) {
-			mViewSwitchListener
-					.onSwitched(mLoadedViews.get(mCurrentBufferIndex),
-							mCurrentAdapterIndex);
+			mViewSwitchListener.onSwitched(currentView, mCurrentAdapterIndex);
 		}
 	}
 
 	private void resetFocus() {
 		logBuffer();
 		recycleViews();
 		removeAllViewsInLayout();
+		mLazyInit.addAll(EnumSet.allOf(LazyInit.class));
 
 		for (int i = Math.max(0, mCurrentAdapterIndex - mSideBuffer); i < Math
 				.min(mAdapter.getCount(), mCurrentAdapterIndex + mSideBuffer
 						+ 1); i++) {
 			mLoadedViews.addLast(makeAndAddView(i, true));
-			if (i == mCurrentAdapterIndex)
+			if (i == mCurrentAdapterIndex) {
 				mCurrentBufferIndex = mLoadedViews.size() - 1;
+				if (mViewInitializeListener != null)
+					mViewInitializeListener.onViewLazyInitialize(mLoadedViews.getLast(), mCurrentAdapterIndex);
+			}
 		}
 		logBuffer();
 		requestLayout();
@@ -587,6 +627,8 @@ private void postViewSwitched(int direction) {
 		if (direction > 0) { // to the right
 			mCurrentAdapterIndex++;
 			mCurrentBufferIndex++;
+			mLazyInit.remove(LazyInit.LEFT);
+			mLazyInit.add(LazyInit.RIGHT);
 
 			// Recycle view outside buffer range
 			if (mCurrentAdapterIndex > mSideBuffer) {
@@ -602,6 +644,8 @@ private void postViewSwitched(int direction) {
 		} else { // to the left
 			mCurrentAdapterIndex--;
 			mCurrentBufferIndex--;
+			mLazyInit.add(LazyInit.LEFT);
+			mLazyInit.remove(LazyInit.RIGHT);
 
 			// Recycle view outside buffer range
 			if (mAdapter.getCount() - 1 - mCurrentAdapterIndex > mSideBuffer) {