Android custom sliding viewgroup up and down, Android custom ViewGroup to achieve elastic sliding effect

Customize View to achieve an elastic sliding effect，for your reference，The specific content is as follows

Implementation principle

Measure all sub-Views in onMeasure()

@Override

protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {

// Measure all child Views

int count = getChildCount();

for (int i = 0; i <count; i++) {

View childView = getChildAt(i);

measureChild( childView, widthMeasureSpec, heightMeasureSpec);

}

setMeasuredDimension(widthMeasureSpec, heightMeasureSpec);

}

onLayout(), will All sub-Views are arranged in order of position

@Override

protected void onLayout(boolean changed, int l, int t, int r, int b) {

// Set the height of ViewGroup and arrange all child Views

int childCount = getChildCount();

MarginLayoutParams params = ( MarginLayoutParams) getLayoutParams();

params.height = mScreenHeight * childCount;

for (int i = 0; i <childCount; i+& #43;) {

View childView = getChildAt(i);

if (childView.getVisibility() != View.GONE) {

// Place each ChildView at the specified position

childView.layout(l, i * mScreenHeight, r, (i + 1) * mScreenHeight);

}

}

}

handle sliding in onTouchEvent()

@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()) {

// Terminate sliding

mScroller.abortAnimation();

}

int offsetY = (int) (mLastY – event.getY());

Log.d(TAG, “onTouchEvent: getScrollY: ” + getScrollY());

Log.d(TAG, “onTouchEvent: offsetY ” + offsetY);

// Reach the top, use offset to judge direction

if (getScrollY () + offsetY <0) { // The current Y position of the slide

offsetY = 0;

}

// Bottom reached

if (getScrollY() > getHeight() – mScreenHeight && offsetY > 0) {

offsetY = 0;

}

}

scrollBy(0, offsetY);

// After sliding, reset the LastY position

mLastY = (int) event.getY();

break;

case MotionEvent.ACTION_UP:

mEnd = getScrollY();

int distance = mEnd – mStart;

if (distance > 0) { // slide up

if (distance <mScreenHeight / 3) {

Log.d(TAG , “onTouchEvent: distance <screen/3");

// Return to the original position

mScroller.startScroll(0, getScrollY(), 0, -distance);

// p>

} else {

// Scroll to the rest 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);

p>}

}

postInvalidate();

}

return super.onTouchEvent(event);

p>}

The ACTION_UP code is for elastic sliding

case MotionEvent.ACTION_UP:

mEnd = getScrollY();

mEnd = getScrollY();

p>

int distance = mEnd – mStart;

if (distance > 0) { // slide up

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 rest of the screen

mScroller.startScroll(0, getScrollY() , 0, mScreenHeight – distance);

}

} else { // slide down

if (-distance <mScreenHeight / 3) {

} p>

mScroller.startScroll(0, getScrollY(), 0, -distance);

} else {

mScroller.startScroll(0, getScrollY(), 0, -mScreenHeight – distance);

}

}

postInvalidate();

Complete code

public class ScrollViewGroup extends ViewGroup {

private static final String TAG = “ScrollView”;

private Scroller mScroller;

private int mScreenHeight; // window Height

private int mLastY;

private int mStart;

private int mEnd;

public ScrollViewGroup(Context context) {

p>

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);

//Get screen height

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) {

// Measure all child Views

int count = getChildCount();

for (int i = 0; i <count; i++) {

View childView = getChildAt(i);

measureChild(childView, widthMeasureSpec, heightMeasureSpec);

p>

}

setMeasuredDimension(widthMeasureSpec, heightMeasureSpec);

}

@Override

protected void onLayout (boolean changed, int l, int t, int r, int b) {

// Set the height of ViewGroup, arrange all child Views

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) {

// Place each ChildView at the specified position

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()) {

// Terminate sliding

mScroller.abortAnimation();

}

int offsetY = (int) (mLastY – event.getY());

Log.d(TAG, “onTouchEvent: getScrollY: ” + getScrollY ());

Log.d(TAG, “onTouchEvent: offsetY ” + offsetY);

// reach the top, use offset to judge the direction

if (getScrollY() + offsetY <0) { // The current Y position that has been slid

offsetY = 0;

}

// Reach the bottom

if (getScrollY() > getHeight() – mScreenHeight && offsetY > 0) {

offsetY = 0;

}

scrollBy(0, offsetY);

// After sliding, reset the LastY position

mLastY = (int) event .getY();

break;

case MotionEvent.ACTION_UP:

mEnd = getScrollY();

int distance = mEnd – mStart;

if (distance > 0) { // slide up

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 rest 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();

}

}

}

}

The above is the whole content of this article ， I hope it will be helpful to your study，