Java tutorial
/* * Copyright (c) 2014,KJFrameForAndroid Open Source Project,. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package org.kymjs.kjframe.widget; import android.content.Context; import android.support.v4.view.ViewPager; import android.util.AttributeSet; import android.view.MotionEvent; import android.view.VelocityTracker; import android.view.View; import android.view.ViewConfiguration; import android.widget.Scroller; /** * ???,?ViewPager??? * <p/> * <b></b> 2014-9-12 * * @author kymjs (https://github.com/kymjs) * @version 1.0 */ public class KJViewPager extends ViewPager { private Scroller mScroller; private VelocityTracker mVelocityTracker; private int mCurScreen; private final int mDefaultScreen = 0; private static final int TOUCH_STATE_REST = 0; private static final int TOUCH_STATE_SCROLLING = 1; private static final int SNAP_VELOCITY = 600; private int mTouchState = TOUCH_STATE_REST; private int mTouchSlop; private float mLastMotionX; private float mLastMotionY; private OnViewChangeListener mOnViewChangeListener; /** * ??? */ private boolean isScroll = true; public KJViewPager(Context context, AttributeSet attrs) { this(context, attrs, 0); } public KJViewPager(Context context, AttributeSet attrs, int defStyle) { super(context, attrs); mScroller = new Scroller(context); mCurScreen = mDefaultScreen; mTouchSlop = ViewConfiguration.get(getContext()).getScaledTouchSlop(); } /** * ??? */ @Override protected void onLayout(boolean changed, int l, int t, int r, int b) { int childLeft = 0; final int childCount = getChildCount(); for (int i = 0; i < childCount; i++) { final View childView = getChildAt(i); if (childView.getVisibility() != View.GONE) { final int childWidth = childView.getMeasuredWidth(); childView.layout(childLeft, 0, childLeft + childWidth, childView.getMeasuredHeight()); childLeft += childWidth; } } } @Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { super.onMeasure(widthMeasureSpec, heightMeasureSpec); final int width = MeasureSpec.getSize(widthMeasureSpec); // final int widthMode = MeasureSpec.getMode(widthMeasureSpec); // if (widthMode != MeasureSpec.EXACTLY) { // throw new IllegalStateException( // "ScrollLayout only canmCurScreen run at EXACTLY mode!"); // } // final int heightMode = MeasureSpec.getMode(heightMeasureSpec); // if (heightMode != MeasureSpec.EXACTLY) { // throw new IllegalStateException( // "ScrollLayout only can run at EXACTLY mode!"); // } // The children are given the same width and height as the scrollLayout final int count = getChildCount(); for (int i = 0; i < count; i++) { getChildAt(i).measure(widthMeasureSpec, heightMeasureSpec); } // Log.e(TAG, "moving to screen "+mCurScreen); scrollTo(mCurScreen * width, 0); } /** * According to the position of current layout scroll to the destination * page. */ public void snapToDestination() { final int screenWidth = getWidth(); final int destScreen = (getScrollX() + screenWidth / 2) / screenWidth; snapToScreen(destScreen); } public void snapToScreen(int whichScreen) { // ?? if (!isScroll) { setToScreen(whichScreen); } else { scrollToScreen(whichScreen); } } public void scrollToScreen(int whichScreen) { // get the valid layout page whichScreen = Math.max(0, Math.min(whichScreen, getChildCount() - 1)); if (getScrollX() != (whichScreen * getWidth())) { final int delta = whichScreen * getWidth() - getScrollX(); mScroller.startScroll(getScrollX(), 0, delta, 0, Math.abs(delta) * 1);// ? ?? mCurScreen = whichScreen; invalidate(); // Redraw the layout if (mOnViewChangeListener != null) { mOnViewChangeListener.OnViewChange(mCurScreen); } } } public void setToScreen(int whichScreen) { whichScreen = Math.max(0, Math.min(whichScreen, getChildCount() - 1)); mCurScreen = whichScreen; scrollTo(whichScreen * getWidth(), 0); if (mOnViewChangeListener != null) { mOnViewChangeListener.OnViewChange(mCurScreen); } } public int getCurScreen() { return mCurScreen; } @Override public void computeScroll() { if (mScroller.computeScrollOffset()) { scrollTo(mScroller.getCurrX(), mScroller.getCurrY()); postInvalidate(); } } @Override public boolean onTouchEvent(MotionEvent event) { if (!isScroll) { return false; } if (mVelocityTracker == null) { mVelocityTracker = VelocityTracker.obtain(); } mVelocityTracker.addMovement(event); final int action = event.getAction(); final float x = event.getX(); final float y = event.getY(); switch (action) { case MotionEvent.ACTION_DOWN: if (!mScroller.isFinished()) { mScroller.abortAnimation(); } mLastMotionX = x; mLastMotionY = y; break; case MotionEvent.ACTION_MOVE: int deltaX = (int) (mLastMotionX - x); int deltaY = (int) (mLastMotionY - y); if (Math.abs(deltaX) < 200 && Math.abs(deltaY) > 10) break; mLastMotionY = y; mLastMotionX = x; scrollBy(deltaX, 0); break; case MotionEvent.ACTION_UP: // if (mTouchState == TOUCH_STATE_SCROLLING) { final VelocityTracker velocityTracker = mVelocityTracker; velocityTracker.computeCurrentVelocity(1000); int velocityX = (int) velocityTracker.getXVelocity(); if (velocityX > SNAP_VELOCITY && mCurScreen > 0) { // Fling enough to move left snapToScreen(mCurScreen - 1); } else if (velocityX < -SNAP_VELOCITY && mCurScreen < getChildCount() - 1) { // Fling enough to move right snapToScreen(mCurScreen + 1); } else { snapToDestination(); } if (mVelocityTracker != null) { mVelocityTracker.recycle(); mVelocityTracker = null; } mTouchState = TOUCH_STATE_REST; break; case MotionEvent.ACTION_CANCEL: mTouchState = TOUCH_STATE_REST; break; } return true; } @Override public boolean onInterceptTouchEvent(MotionEvent ev) { if (!isScroll) { return false; } final int action = ev.getAction(); if ((action == MotionEvent.ACTION_MOVE) && (mTouchState != TOUCH_STATE_REST)) { return true; } final float x = ev.getX(); final float y = ev.getY(); switch (action) { case MotionEvent.ACTION_MOVE: final int xDiff = (int) Math.abs(mLastMotionX - x); if (xDiff > mTouchSlop) { mTouchState = TOUCH_STATE_SCROLLING; } break; case MotionEvent.ACTION_DOWN: mLastMotionX = x; mLastMotionY = y; mTouchState = mScroller.isFinished() ? TOUCH_STATE_REST : TOUCH_STATE_SCROLLING; break; case MotionEvent.ACTION_CANCEL: case MotionEvent.ACTION_UP: mTouchState = TOUCH_STATE_REST; break; } return mTouchState != TOUCH_STATE_REST; } @Override public boolean dispatchTouchEvent(MotionEvent ev) { boolean ret = super.dispatchTouchEvent(ev); if (ret) { requestDisallowInterceptTouchEvent(true); } return ret; } /** * ??? * * @param listener */ public void setOnViewChangeListener(OnViewChangeListener listener) { mOnViewChangeListener = listener; } /** * ??? */ public interface OnViewChangeListener { public void OnViewChange(int view); } /** * ??? * * @param scroll */ public void setCanScroll(boolean scroll) { this.isScroll = scroll; } }