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The source code is released under:
Apache License
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package tree.love.draglayout.drag; //from w ww.j av a 2 s. co m import android.content.Context; import android.support.v4.view.MotionEventCompat; import android.support.v4.view.ViewCompat; import android.support.v4.widget.ViewDragHelper; import android.util.AttributeSet; import android.util.Log; import android.view.MotionEvent; import android.view.View; import android.view.ViewGroup; import tree.love.draglayout.R; /** Created by wuyexiong on 13-8-31. */ public class YoutubeLayout extends ViewGroup{ private static final String TAG = "YoutubeLayout"; private static final int MIN_FLING_VELOCITY = 400; // dips per second private View mHeaderView; private View mDescView; private float mInitialMotionX; private float mInitialMotionY; private int mDragRange; private int mTop; private float mDragOffset; private ViewDragHelper mDragHelper; public YoutubeLayout(Context context) { super(context); init(context); } public YoutubeLayout(Context context, AttributeSet attrs) { super(context, attrs); init(context); } public YoutubeLayout(Context context, AttributeSet attrs, int defStyle) { super(context, attrs, defStyle); init(context); } private void init(Context context) { final float density = context.getResources().getDisplayMetrics().density; mDragHelper = ViewDragHelper.create(this, 1.0f, new DragHelperCallback()); mDragHelper.setMinVelocity(MIN_FLING_VELOCITY * density); } public void maximize() { smoothSlideTo(0.0f); } public void minimize() { smoothSlideTo(1.0f); } private boolean smoothSlideTo(float slideOffset) { final int topBound = getPaddingTop(); int y = (int) (topBound + slideOffset * mDragRange); if(mDragHelper.smoothSlideViewTo(mHeaderView, mHeaderView.getLeft(), y)) { ViewCompat.postInvalidateOnAnimation(this); return true; } return false; } @Override protected void onFinishInflate() { Log.d(TAG, "onFInishInflate"); mHeaderView = findViewById(R.id.viewHeader); mDescView = findViewById(R.id.viewDesc); } @Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { // Log.d(TAG, "onMeasure"); measureChildren(widthMeasureSpec, heightMeasureSpec); int maxWidth = MeasureSpec.getSize(widthMeasureSpec); int maxHeight = MeasureSpec.getSize(heightMeasureSpec); setMeasuredDimension(resolveSizeAndState(maxWidth, widthMeasureSpec, 0), resolveSizeAndState(maxHeight, heightMeasureSpec, 0)); super.onMeasure(widthMeasureSpec, heightMeasureSpec); } @Override protected void onLayout(boolean changed, int l, int t, int r, int b) { int parentViewHeight = getHeight(); int dragViewHeight = mHeaderView.getMeasuredHeight(); mDragRange = parentViewHeight - dragViewHeight; // Log.d(TAG, "onLayout:" + "changed:" + changed + ",l:" + l + ",t:" + t + ",r:" + r + ",b:" + b + ",mDragRange" + mDragRange); mHeaderView.layout( 0, mTop, r, mTop + mHeaderView.getMeasuredHeight()); mDescView.layout( 0, mTop + mHeaderView.getMeasuredHeight(), r, mTop + b); } private class DragHelperCallback extends ViewDragHelper.Callback { @Override public boolean tryCaptureView(View child, int pointerId) { return child == mHeaderView; } @Override public void onViewPositionChanged(View changedView, int left, int top, int dx, int dy) { // Log.i(TAG, "onViewPositionChanged:" + "left:" + left + ",top:" + top + ",dx:" + dx + ",dy:" + dy); mTop = top; mDragOffset = (float) top / mDragRange; // Log.i(TAG, "onViewPositionChanged:" + "mDragOffset:" + mDragOffset); mHeaderView.setPivotX(mHeaderView.getWidth()); mHeaderView.setPivotY(mHeaderView.getHeight()); mHeaderView.setScaleX(1 - mDragOffset / 2); mHeaderView.setScaleY(1 - mDragOffset / 2); mDescView.setAlpha(1 - mDragOffset); requestLayout(); } @Override public int clampViewPositionVertical(View child, int top, int dy) { final int topBound = getPaddingTop(); final int bottomBound = getHeight() - mHeaderView.getHeight() - mHeaderView.getPaddingBottom(); final int newTop = Math.min(Math.max(top, topBound), bottomBound); return newTop; } @Override public void onViewReleased(View releasedChild, float xvel, float yvel) { // Log.i(TAG, "onViewReleased:" + "xvel:" + xvel + ",yvel:" + yvel); //yvel Fling?????yvel > 0 ??????Fling || yvel < 0 ??????Fling int top = getPaddingTop(); if (yvel > 0 || (yvel == 0 && mDragOffset > 0.4f)/* ???????????????????????????????????????????? */) { top += mDragRange; } mDragHelper.settleCapturedViewAt(releasedChild.getLeft(), top); invalidate();//important ??????????View???? ????????????????????????? } @Override public int getViewVerticalDragRange(View child) { return mDragRange; } } @Override public void computeScroll() { if(mDragHelper.continueSettling(true)) { ViewCompat.postInvalidateOnAnimation(this); } } @Override public boolean onInterceptTouchEvent(MotionEvent ev) { final int action = MotionEventCompat.getActionMasked(ev); if(action != MotionEvent.ACTION_DOWN) { mDragHelper.cancel(); return super.onInterceptTouchEvent(ev); } if(action == MotionEvent.ACTION_CANCEL || action == MotionEvent.ACTION_UP) { mDragHelper.cancel(); return false; } final float x = ev.getX(); final float y = ev.getY(); boolean interceptTap = false; switch(action) { case MotionEvent.ACTION_DOWN: mInitialMotionX = x; mInitialMotionY = y; interceptTap = mDragHelper.isViewUnder(mHeaderView, (int) x, (int) y); break; case MotionEvent.ACTION_MOVE: final float adx = Math.abs(x - mInitialMotionX); final float ady = Math.abs(y - mInitialMotionY); final int slop = mDragHelper.getTouchSlop(); if(ady > slop && adx > ady) { mDragHelper.cancel(); return false; } break; } return mDragHelper.shouldInterceptTouchEvent(ev) || interceptTap; } @Override public boolean onTouchEvent(MotionEvent event) { mDragHelper.processTouchEvent(event); final int action = event.getAction(); final float x = event.getX(); final float y = event.getY(); //???????????HeaderView? boolean isHeaderViewUnder = mDragHelper.isViewUnder(mHeaderView, (int)x, (int)y); switch(action & MotionEventCompat.ACTION_MASK) { case MotionEvent.ACTION_DOWN: { mInitialMotionX = x; mInitialMotionY = y; break; } case MotionEvent.ACTION_UP: { final float dx = x - mInitialMotionX; final float dy = y - mInitialMotionY; final float slop = mDragHelper.getTouchSlop(); // Log.i(TAG, "dx * dx + dy * dy = " + dx * dx + dy * dy); // Log.i(TAG, "slop * slop = " + slop * slop); // Log.i(TAG, "mDragOffset:" + mDragOffset); if(dx * dx + dy * dy < slop * slop && isHeaderViewUnder) { if (mDragOffset == 0) { minimize(); } else { maximize(); } } break; } } return isHeaderViewUnder && isViewHit(mHeaderView, (int) x, (int) y) || isViewHit(mDescView, (int) x, (int) y); } private boolean isViewHit(View view, int x, int y) { int[] viewLocation = new int[2]; view.getLocationOnScreen(viewLocation); int[] parentLocation = new int[2]; this.getLocationOnScreen(parentLocation); int screenX = parentLocation[0] + x; int screenY = parentLocation[1] + y; return screenX >= viewLocation[0] && screenX < viewLocation[0] + view.getWidth() && screenY >= viewLocation[1] && screenY < viewLocation[1] + view.getHeight(); } }