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The source code is released under:
Apache License
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package com.glasstunes.screenslide; //www . ja v a 2 s .co m import android.animation.Animator; import android.animation.Animator.AnimatorListener; import android.animation.ObjectAnimator; import android.content.Context; import android.content.res.TypedArray; import android.graphics.Camera; import android.support.v4.view.MotionEventCompat; import android.support.v4.view.ViewConfigurationCompat; import android.support.v4.view.ViewPager; import android.util.AttributeSet; import android.view.MotionEvent; import android.view.View; import android.view.ViewConfiguration; import android.view.animation.DecelerateInterpolator; import android.view.animation.Transformation; import com.glasstunes.R; public class BounceBackViewPager extends ViewPager { /** * maximum z distance to translate child view */ final static int DEFAULT_OVERSCROLL_TRANSLATION = 150; /** * duration of overscroll animation in ms */ final private static int DEFAULT_OVERSCROLL_ANIMATION_DURATION = 400; @SuppressWarnings("unused") private final static String DEBUG_TAG = ViewPager.class.getSimpleName(); private final static int INVALID_POINTER_ID = -1; /** * * @author renard, extended by Piotr Zawadzki * */ private class OverscrollEffect { private float mOverscroll; private Animator mAnimator; /** * @param deltaDistance * [0..1] 0->no overscroll, 1>full overscroll */ public void setPull(final float deltaDistance) { mOverscroll = deltaDistance; invalidateVisibleChilds(mLastPosition); } /** * called when finger is released. starts to animate back to default * position */ private void onRelease() { if (mAnimator != null && mAnimator.isRunning()) { mAnimator.addListener(new AnimatorListener() { @Override public void onAnimationStart(Animator animation) { } @Override public void onAnimationRepeat(Animator animation) { } @Override public void onAnimationEnd(Animator animation) { startAnimation(0); } @Override public void onAnimationCancel(Animator animation) { } }); mAnimator.cancel(); } else { startAnimation(0); } } private void startAnimation(final float target) { mAnimator = ObjectAnimator.ofFloat(this, "pull", mOverscroll, target); mAnimator.setInterpolator(new DecelerateInterpolator()); final float scale = Math.abs(target - mOverscroll); mAnimator .setDuration((long) (mOverscrollAnimationDuration * scale)); mAnimator.start(); } private boolean isOverscrolling() { if (mScrollPosition == 0 && mOverscroll < 0) { return true; } final boolean isLast = (getAdapter().getCount() - 1) == mScrollPosition; if (isLast && mOverscroll > 0) { return true; } return false; } } final private OverscrollEffect mOverscrollEffect = new OverscrollEffect(); final private Camera mCamera = new Camera(); private OnPageChangeListener mScrollListener; private float mLastMotionX; private int mActivePointerId; private int mScrollPosition; private float mScrollPositionOffset; final private int mTouchSlop; private float mOverscrollTranslation; private int mOverscrollAnimationDuration; public BounceBackViewPager(Context context, AttributeSet attrs) { super(new ContextWrapperEdgeEffect(context), attrs); setStaticTransformationsEnabled(true); final ViewConfiguration configuration = ViewConfiguration.get(context); mTouchSlop = ViewConfigurationCompat .getScaledPagingTouchSlop(configuration); super.setOnPageChangeListener(new MyOnPageChangeListener()); setOverScrollMode(OVER_SCROLL_ALWAYS); init(attrs); } private void init(AttributeSet attrs) { TypedArray a = getContext().obtainStyledAttributes(attrs, R.styleable.BounceBackViewPager); mOverscrollTranslation = a.getDimension( R.styleable.BounceBackViewPager_overscroll_translation, DEFAULT_OVERSCROLL_TRANSLATION); mOverscrollAnimationDuration = a.getInt( R.styleable.BounceBackViewPager_overscroll_animation_duration, DEFAULT_OVERSCROLL_ANIMATION_DURATION); a.recycle(); } public int getOverscrollAnimationDuration() { return mOverscrollAnimationDuration; } public void setOverscrollAnimationDuration(int mOverscrollAnimationDuration) { this.mOverscrollAnimationDuration = mOverscrollAnimationDuration; } public float getOverscrollTranslation() { return mOverscrollTranslation; } public void setOverscrollTranslation(int mOverscrollTranslation) { this.mOverscrollTranslation = mOverscrollTranslation; } @Override public void setOnPageChangeListener(OnPageChangeListener listener) { mScrollListener = listener; }; private void invalidateVisibleChilds(final int position) { for (int i = 0; i < getChildCount(); i++) { getChildAt(i).invalidate(); } // this.invalidate(); // final View child = getChildAt(position); // final View previous = getChildAt(position - 1); // final View next = getChildAt(position + 1); // if (child != null) { // child.invalidate(); // } // if (previous != null) { // previous.invalidate(); // } // if (next != null) { // next.invalidate(); // } } private int mLastPosition = 0; private class MyOnPageChangeListener implements OnPageChangeListener { @Override public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) { if (mScrollListener != null) { mScrollListener.onPageScrolled(position, positionOffset, positionOffsetPixels); } mScrollPosition = position; mScrollPositionOffset = positionOffset; mLastPosition = position; invalidateVisibleChilds(position); } @Override public void onPageSelected(int position) { if (mScrollListener != null) { mScrollListener.onPageSelected(position); } } @Override public void onPageScrollStateChanged(final int state) { if (mScrollListener != null) { mScrollListener.onPageScrollStateChanged(state); } if (state == SCROLL_STATE_IDLE) { mScrollPositionOffset = 0; } } } @Override public boolean onInterceptTouchEvent(MotionEvent ev) { try { final int action = ev.getAction() & MotionEventCompat.ACTION_MASK; switch (action) { case MotionEvent.ACTION_DOWN: { mLastMotionX = ev.getX(); mActivePointerId = MotionEventCompat.getPointerId(ev, 0); break; } case MotionEventCompat.ACTION_POINTER_DOWN: { final int index = MotionEventCompat.getActionIndex(ev); final float x = MotionEventCompat.getX(ev, index); mLastMotionX = x; mActivePointerId = MotionEventCompat.getPointerId(ev, index); break; } } return super.onInterceptTouchEvent(ev); } catch (IllegalArgumentException e) { e.printStackTrace(); return false; } catch (ArrayIndexOutOfBoundsException e) { e.printStackTrace(); return false; } } @Override public boolean dispatchTouchEvent(MotionEvent ev) { try { return super.dispatchTouchEvent(ev); } catch (IllegalArgumentException e) { e.printStackTrace(); return false; } catch (ArrayIndexOutOfBoundsException e) { e.printStackTrace(); return false; } } @Override public boolean onTouchEvent(MotionEvent ev) { boolean callSuper = false; final int action = ev.getAction(); switch (action) { case MotionEvent.ACTION_DOWN: { callSuper = true; mLastMotionX = ev.getX(); mActivePointerId = MotionEventCompat.getPointerId(ev, 0); break; } case MotionEventCompat.ACTION_POINTER_DOWN: { callSuper = true; final int index = MotionEventCompat.getActionIndex(ev); final float x = MotionEventCompat.getX(ev, index); mLastMotionX = x; mActivePointerId = MotionEventCompat.getPointerId(ev, index); break; } case MotionEvent.ACTION_MOVE: { if (mActivePointerId != INVALID_POINTER_ID) { // Scroll to follow the motion event final int activePointerIndex = MotionEventCompat .findPointerIndex(ev, mActivePointerId); final float x = MotionEventCompat.getX(ev, activePointerIndex); final float deltaX = mLastMotionX - x; final float oldScrollX = getScrollX(); final int width = getWidth(); final int widthWithMargin = width + getPageMargin(); final int lastItemIndex = getAdapter().getCount() - 1; final int currentItemIndex = getCurrentItem(); final float leftBound = Math.max(0, (currentItemIndex - 1) * widthWithMargin); final float rightBound = Math.min(currentItemIndex + 1, lastItemIndex) * widthWithMargin; final float scrollX = oldScrollX + deltaX; if (mScrollPositionOffset == 0) { if (scrollX < leftBound) { if (leftBound == 0) { final float over = deltaX + mTouchSlop; mOverscrollEffect.setPull(over / width); } } else if (scrollX > rightBound) { if (rightBound == lastItemIndex * widthWithMargin) { final float over = scrollX - rightBound - mTouchSlop; mOverscrollEffect.setPull(over / width); } } } else { mLastMotionX = x; } } else { mOverscrollEffect.onRelease(); } break; } case MotionEvent.ACTION_UP: case MotionEvent.ACTION_CANCEL: { callSuper = true; mActivePointerId = INVALID_POINTER_ID; mOverscrollEffect.onRelease(); break; } case MotionEvent.ACTION_POINTER_UP: { final int pointerIndex = (ev.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK) >> MotionEvent.ACTION_POINTER_INDEX_SHIFT; final int pointerId = MotionEventCompat.getPointerId(ev, pointerIndex); if (pointerId == mActivePointerId) { // This was our active pointer going up. Choose a new // active pointer and adjust accordingly. final int newPointerIndex = pointerIndex == 0 ? 1 : 0; mLastMotionX = ev.getX(newPointerIndex); mActivePointerId = MotionEventCompat.getPointerId(ev, newPointerIndex); callSuper = true; } break; } } if (mOverscrollEffect.isOverscrolling() && !callSuper) { return true; } else { return super.onTouchEvent(ev); } } @Override protected boolean getChildStaticTransformation(View child, Transformation t) { if (child.getWidth() == 0) { return false; } final int position = child.getLeft() / child.getWidth(); final boolean isFirstOrLast = position == 0 || (position == getAdapter().getCount() - 1); if (mOverscrollEffect.isOverscrolling() && isFirstOrLast) { final float dx = getWidth() / 2; final int dy = getHeight() / 2; t.getMatrix().reset(); final float translateX = mOverscrollTranslation * (mOverscrollEffect.mOverscroll > 0 ? Math.min( mOverscrollEffect.mOverscroll, 1) : Math.max( mOverscrollEffect.mOverscroll, -1)); mCamera.save(); mCamera.translate(-translateX, 0, 0); mCamera.getMatrix(t.getMatrix()); mCamera.restore(); t.getMatrix().preTranslate(-dx, -dy); t.getMatrix().postTranslate(dx, dy); if (getChildCount() == 1) { this.invalidate(); } else { child.invalidate(); } return true; } return false; } }