Shulou(Shulou.com)06/01 Report--

This article mainly explains "how to achieve an elastic sliding effect through custom ViewGroup in Android". Interested friends may wish to have a look. The method introduced in this paper is simple, fast and practical. Let's let the editor take you to learn how to achieve an elastic sliding effect through custom ViewGroup in Android.

Realization principle

Measure all child View in onMeasure ()

@ Override protected void onMeasure (int widthMeasureSpec, int heightMeasureSpec) {/ / measure all children View int count = getChildCount (); for (int I = 0; I

< count; i++) { View childView = getChildAt(i); measureChild(childView, widthMeasureSpec, heightMeasureSpec); } setMeasuredDimension(widthMeasureSpec, heightMeasureSpec); } onLayout()中,将所有的子View按照位置依次往下排列 @Override protected void onLayout(boolean changed, int l, int t, int r, int b) { // 设置ViewGroup的高度,对所有子View进行排列 int childCount = getChildCount(); MarginLayoutParams params = (MarginLayoutParams) getLayoutParams(); params.height = mScreenHeight * childCount; for (int i = 0; i < childCount; i++) { View childView = getChildAt(i); if (childView.getVisibility() != View.GONE) { // 给每个ChildView放置在指定位置 childView.layout(l, i * mScreenHeight, r, (i + 1) * mScreenHeight); } } } onTouchEvent()中处理滑动 @Override public boolean onTouchEvent(MotionEvent event) { switch (event.getAction()) { case MotionEvent.ACTION_DOWN: mLastY = (int) event.getY(); mStart = getScrollY(); return true; case MotionEvent.ACTION_MOVE: if (!mScroller.isFinished()) { // 终止滑动 mScroller.abortAnimation(); } int offsetY = (int) (mLastY - event.getY()); Log.d(TAG, "onTouchEvent: getScrollY: " + getScrollY()); Log.d(TAG, "onTouchEvent: offsetY " + offsetY); // 到达顶部,使用offset判断方向 if (getScrollY() + offsetY < 0) { // 当前已经滑动的 Y 位置 offsetY = 0; } // 到达底部 if (getScrollY() >

GetHeight ()-mScreenHeight & & offsetY > 0) {offsetY = 0;} scrollBy (0, offsetY); / / reset LastY position mLastY = (int) event.getY (); break; case MotionEvent.ACTION_UP: mEnd = getScrollY (); int distance = mEnd-mStart; if (distance > 0) {/ / upward slide if (distance)

< mScreenHeight / 3) { Log.d(TAG, "onTouchEvent: distance < screen/3"); // 回到原来位置 mScroller.startScroll(0, getScrollY(), 0, -distance); } else { // 滚到屏幕的剩余位置 mScroller.startScroll(0, getScrollY(), 0, mScreenHeight - distance); } } else { // 向下滑动 if (-distance < mScreenHeight / 3) { mScroller.startScroll(0, getScrollY(), 0, -distance); } else { mScroller.startScroll(0, getScrollY(), 0, -mScreenHeight - distance); } } postInvalidate(); } return super.onTouchEvent(event); } 其中ACTION_UP这段代码是处理弹性滑动的 case MotionEvent.ACTION_UP: mEnd = getScrollY(); int distance = mEnd - mStart; if (distance >

0) {/ / slide if up (distance

< mScreenHeight / 3) { Log.d(TAG, "onTouchEvent: distance < screen/3"); // 回到原来位置 mScroller.startScroll(0, getScrollY(), 0, -distance); } else { // 滚到屏幕的剩余位置 mScroller.startScroll(0, getScrollY(), 0, mScreenHeight - distance); } } else { // 向下滑动 if (-distance < mScreenHeight / 3) { mScroller.startScroll(0, getScrollY(), 0, -distance); } else { mScroller.startScroll(0, getScrollY(), 0, -mScreenHeight - distance); } } postInvalidate(); 完整代码 public class ScrollViewGroup extends ViewGroup { private static final String TAG = "ScrollView"; private Scroller mScroller; private int mScreenHeight; // 窗口高度 private int mLastY; private int mStart; private int mEnd; public ScrollViewGroup(Context context) { this(context, null); } public ScrollViewGroup(Context context, AttributeSet attrs) { this(context, attrs, 0); } public ScrollViewGroup(Context context, AttributeSet attrs, int defStyleAttr) { super(context, attrs, defStyleAttr); mScroller = new Scroller(context); // 获取屏幕高度 WindowManager windowManager = (WindowManager) context.getSystemService(Context.WINDOW_SERVICE); DisplayMetrics metrics = new DisplayMetrics(); windowManager.getDefaultDisplay().getMetrics(metrics); mScreenHeight = metrics.heightPixels; Log.d(TAG, "ScrollViewGroup: ScreenHeight " + mScreenHeight); } @Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { // 测量所有子View int count = getChildCount(); for (int i = 0; i < count; i++) { View childView = getChildAt(i); measureChild(childView, widthMeasureSpec, heightMeasureSpec); } setMeasuredDimension(widthMeasureSpec, heightMeasureSpec); } @Override protected void onLayout(boolean changed, int l, int t, int r, int b) { // 设置ViewGroup的高度,对所有子View进行排列 int childCount = getChildCount(); MarginLayoutParams params = (MarginLayoutParams) getLayoutParams(); params.height = mScreenHeight * childCount; for (int i = 0; i < childCount; i++) { View childView = getChildAt(i); if (childView.getVisibility() != View.GONE) { // 给每个ChildView放置在指定位置 childView.layout(l, i * mScreenHeight, r, (i + 1) * mScreenHeight); } } } @Override public boolean onTouchEvent(MotionEvent event) { switch (event.getAction()) { case MotionEvent.ACTION_DOWN: mLastY = (int) event.getY(); mStart = getScrollY(); return true; case MotionEvent.ACTION_MOVE: if (!mScroller.isFinished()) { // 终止滑动 mScroller.abortAnimation(); } int offsetY = (int) (mLastY - event.getY()); Log.d(TAG, "onTouchEvent: getScrollY: " + getScrollY()); Log.d(TAG, "onTouchEvent: offsetY " + offsetY); // 到达顶部,使用offset判断方向 if (getScrollY() + offsetY < 0) { // 当前已经滑动的 Y 位置 offsetY = 0; } // 到达底部 if (getScrollY() >

GetHeight ()-mScreenHeight & & offsetY > 0) {offsetY = 0;} scrollBy (0, offsetY); / / reset LastY position mLastY = (int) event.getY (); break; case MotionEvent.ACTION_UP: mEnd = getScrollY (); int distance = mEnd-mStart If (distance > 0) {/ / slide if (distance < mScreenHeight / 3) {Log.d (TAG, "onTouchEvent: distance < screen/3"); / / return to the original position mScroller.startScroll (0, getScrollY (), 0,-distance);} else {/ / scroll to the remaining position of the screen mScroller.startScroll (0, getScrollY (), 0, mScreenHeight-distance) } else {/ / slide down if (- distance < mScreenHeight / 3) {mScroller.startScroll (0, getScrollY (), 0,-distance);} else {mScroller.startScroll (0, getScrollY (), 0,-mScreenHeight-distance);}} postInvalidate ();} return super.onTouchEvent (event) } @ Override public void computeScroll () {if (mScroller.computeScrollOffset ()) {scrollTo (mScroller.getCurrX (), mScroller.getCurrY ()); postInvalidate ();} so far, I believe you have a deeper understanding of "how to achieve an elastic sliding effect through custom ViewGroup in Android". You might as well do it in practice! Here is the website, more related content can enter the relevant channels to inquire, follow us, continue to learn!

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.