package com.laotan.easyreader.view;
import android.content.Context;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.VelocityTracker;
import android.view.View;
import android.view.ViewGroup;
import android.view.WindowManager;
/**
* Created by laotan on 2017/3/6.
*/
public class HorizontalScrollView extends ViewGroup {
/**
* 每一步我们重点关心每一步新添加的变量。
*/
//2、准备工作
private int windowWidth;
private int halfWindowWidth;//一半的屏幕宽度
private int oneThirdWindowWidth;//三分之一屏幕宽度
//3、重写onLayout排列子View
private int childLeftLeft;//左边第一个的left值
private int childRightLeft;//右边第一个的left值
private int childCount;//子View个数
private int childViewHeightDifference = 50;//我们把子View的高度差设为50
private int childHalfCount;
//4、ViewGroup滑动处理
private int startX;
private int lastX;
private int totalX;
//5、分别让两边子View动起来
private int touchChildCenterCount;//互动时位于屏幕正中间的View
private int leftHigh;
private int rightHigh;
//7、处理滑动和点击事件冲突和添加VelocityTracker
private VelocityTracker mVelocityTracker;
private int scllorTime;
private int dispatchEndX;
private int dispatchEndY;
private int childMarginRight = 10;
private int visualCount = 3;
public HorizontalScrollView(Context context) {
this(context, null);
}
public HorizontalScrollView(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}
public HorizontalScrollView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
init();
}
private void init() {
WindowManager wm = (WindowManager) getContext()
.getSystemService(Context.WINDOW_SERVICE);
windowWidth = wm.getDefaultDisplay().getWidth();//获取屏幕宽度
halfWindowWidth = windowWidth / 2;
oneThirdWindowWidth = windowWidth / visualCount;
mVelocityTracker = VelocityTracker.obtain();
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
measureChildren(widthMeasureSpec, heightMeasureSpec);
int measuredWidth = 0;
int measuredHeight = 0;
final int childCount = getChildCount();
int widthSpecMode = MeasureSpec.getMode(widthMeasureSpec);
int widthSpecSizd = MeasureSpec.getSize(widthMeasureSpec);
int heightSpecMode = MeasureSpec.getMode(heightMeasureSpec);
int heightSpecSizd = MeasureSpec.getSize(heightMeasureSpec);
if (childCount == 0) {
setMeasuredDimension(0, 0);
} else if (widthSpecMode == MeasureSpec.AT_MOST && heightSpecMode == MeasureSpec.AT_MOST) {
final View childView = getChildAt(0);
measuredWidth = oneThirdWindowWidth * childCount;
measuredHeight = childView.getMeasuredHeight();
setMeasuredDimension(measuredWidth, measuredHeight);
} else if (heightSpecMode == MeasureSpec.AT_MOST) {
final View childView = getChildAt(0);
measuredHeight = childView.getMeasuredHeight();
setMeasuredDimension(widthSpecSizd, measuredHeight);
} else if (widthSpecMode == MeasureSpec.AT_MOST) {
final View childView = getChildAt(0);
measuredWidth = oneThirdWindowWidth * childCount;
setMeasuredDimension(measuredWidth, heightSpecSizd);
}
}
@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
childCount = getChildCount();
// if (childCount < 3) {
// try {
// throw new Exception("HorizontalScrollView必须有3个或者3个以上的子View");
// } catch (Exception e) {
// e.printStackTrace();
// }
// }
childLeftLeft = halfWindowWidth;
childRightLeft = halfWindowWidth;
childHalfCount = childCount / 2;
leftHigh = childViewHeightDifference * (childHalfCount);//初始化左边for循环的最左边View的高度位置
rightHigh = childViewHeightDifference * (-childHalfCount);//初始化右边for循环的最左边View的高度位置，需要加上i * childViewHeightDifference
touchChildCenterCount = childHalfCount;
for (int i = childHalfCount; i >= 0; i--) {
childMarginRight = 10;
final View childView = getChildAt(i);
if (childView.getVisibility() != GONE) {
final int childWidth = oneThirdWindowWidth;
childView.layout(childLeftLeft - childWidth / 2, childViewHeightDifference * (childHalfCount - i), childLeftLeft - childWidth / 2 + childWidth - childMarginRight,
childViewHeightDifference * (childHalfCount - i) + childView.getMeasuredHeight());
childLeftLeft -= childWidth;
}
}
for (int i = childHalfCount + 1; i < childCount; i++) {
childMarginRight = 10;
final View childView = getChildAt(i);
if (childView.getVisibility() != GONE) {
final int childWidth = oneThirdWindowWidth;
if (i == childCount - 1) {
childMarginRight = 0;
}
childView.layout(childRightLeft + childWidth / 2, childViewHeightDifference * (i - childHalfCount),
childRightLeft + childWidth / 2 + childWidth - childMarginRight, childViewHeightDifference * (i - childHalfCount) + childView.getMeasuredHeight());
childRightLeft += childWidth;
}
}
}
@Override
public boolean onTouchEvent(MotionEvent event) {
if (getChildCount()<=3){
return true;
}
mVelocityTracker.addMovement(event);
startX = (int) event.getRawX();
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
break;
case MotionEvent.ACTION_MOVE:
int delatX = 0;
//滑动冲突时不能马上获取到滑动的delatX导致突然是一个很大的值没有想到很好的办法，就只能这样子限制delatX了。
if (lastX != 0) {
delatX = startX - lastX;
if (delatX >= 50) {
delatX = 50;
}
if (delatX <= -50) {
delatX = -50;
}
}
totalX += delatX;
scroll();
break;
case MotionEvent.ACTION_UP:
mVelocityTracker.computeCurrentVelocity(1000);
float xVelocity = mVelocityTracker.getXVelocity();
if (Math.abs(xVelocity) >= childViewHeightDifference) {
//以下20和300都是我经过多次测试选取的值，感觉运行代码损失了一些时间所以只能测试找出来不能通过计算。
if (xVelocity > 0) {
scllorTime = 20;
int count = (int) (xVelocity / 300);
int currentTotalX = totalX + count * oneThirdWindowWidth/10;
postDelayed(new AutoScllorRunnable(currentTotalX), 1);
}
if (xVelocity < 0) {
scllorTime = 20;
int count = (int) (Math.abs(xVelocity) / 300);
int currentTotalX = totalX - count * oneThirdWindowWidth/10;
postDelayed(new AutoScllorRunnable(currentTotalX), 1);
}
}
break;
}
lastX = startX;
return true;
}
private void scroll() {
childLeftLeft = halfWindowWidth;
childRightLeft = halfWindowWidth;
if (touchChildCenterCount - childHalfCount >= 1) {
childLeftLeft = halfWindowWidth + (touchChildCenterCount - childHalfCount) * oneThirdWindowWidth;
childRightLeft = halfWindowWidth + (touchChildCenterCount - childHalfCount) * oneThirdWindowWidth;
}
if (touchChildCenterCount - childHalfCount <= -1) {
childLeftLeft = halfWindowWidth + (touchChildCenterCount - childHalfCount) * oneThirdWindowWidth;
childRightLeft = halfWindowWidth + (touchChildCenterCount - childHalfCount) * oneThirdWindowWidth;
}
for (int i = touchChildCenterCount; i >= 0; i--) {
childMarginRight = 10;
final View childView = getChildAt(i);
if (childView.getVisibility() != GONE) {
if (totalX > 0) {
if (i == touchChildCenterCount) {
final int childWidth = oneThirdWindowWidth;
childView.layout(childLeftLeft - childWidth / 2, rightHigh + i * childViewHeightDifference,
childLeftLeft + childWidth / 2 - childMarginRight, rightHigh + i * childViewHeightDifference + childView.getMeasuredHeight());
} else {
final int childWidth = oneThirdWindowWidth;
childView.layout(childLeftLeft - 3 * childWidth / 2, leftHigh - i * childViewHeightDifference,
childLeftLeft - childWidth / 2 - childMarginRight, leftHigh - i * childViewHeightDifference + childView.getMeasuredHeight());
childLeftLeft -= childWidth;
}
} else {
final int childWidth = oneThirdWindowWidth;
childView.layout(childLeftLeft - childWidth / 2, leftHigh - i * childViewHeightDifference,
childLeftLeft + childWidth / 2 - childMarginRight, leftHigh - i * childViewHeightDifference + childView.getMeasuredHeight());
childLeftLeft -= childWidth;
}
}
}
for (int i = touchChildCenterCount + 1; i < childCount; i++) {
final View childView = getChildAt(i);
if (childView.getVisibility() != GONE) {
final int childWidth = oneThirdWindowWidth;
childMarginRight = 10;
if (i == childCount - 1) {
childMarginRight = 0;
}
childView.layout(childRightLeft + childWidth / 2, rightHigh + i * childViewHeightDifference,
childRightLeft + childWidth / 2 + childWidth - childMarginRight, rightHigh + i * childViewHeightDifference + childView.getMeasuredHeight());
childRightLeft += childWidth;
}
}
//控制范围
if ((childCount - visualCount) % 2 == 0) {
int totalXRange = windowWidth / visualCount * (childCount - visualCount) / 2;
if (totalX <= -totalXRange) {
totalX = -totalXRange;
}
if (totalX >= totalXRange) {
totalX = totalXRange;
}
} else {
int totalXRange = (int) (windowWidth / visualCount * ((childCount - visualCount) / 2 + 0.5));
if (totalX >= totalXRange + windowWidth / (visualCount*2)) {
totalX = totalXRange + windowWidth / (visualCount*2);
}
if (totalX <= windowWidth / (visualCount*2) - totalXRange) {
totalX = windowWidth / (visualCount*2) - totalXRange;
}
}
if (totalX * oneThirdWindowWidth >= 1 || totalX * oneThirdWindowWidth <= -1) {
touchChildCenterCount = childHalfCount - totalX / oneThirdWindowWidth;
}
if (totalX * oneThirdWindowWidth == 0) {
touchChildCenterCount = childHalfCount;
}
leftHigh = -totalX * childViewHeightDifference / oneThirdWindowWidth + childViewHeightDifference * (childHalfCount);
rightHigh = totalX * childViewHeightDifference / oneThirdWindowWidth + childViewHeightDifference * (-childHalfCount);
scrollTo(-totalX, 0);//左右滑动实际上是滑动ViewGroup的内容。
}
@Override
public boolean dispatchTouchEvent(MotionEvent ev) {
//打开注释就可以在这个控件得到上下滑动的事件，不过我们这个控件的需求基本是左右滑动打开的话会影响体验。
int dispatchStartX = (int) ev.getX();
int dispatchStartY = (int) ev.getY();
switch (ev.getAction()) {
case MotionEvent.ACTION_DOWN:
getParent().requestDisallowInterceptTouchEvent(true);
break;
case MotionEvent.ACTION_MOVE:
int deltax = dispatchEndX - dispatchStartX;
int deltaY = dispatchEndY - dispatchStartY;
if (Math.abs(deltaY) <= Math.abs(deltax)) {
getParent().requestDisallowInterceptTouchEvent(true);
} else {
getParent().requestDisallowInterceptTouchEvent(false);
}
break;
case MotionEvent.ACTION_UP:
break;
}
dispatchEndX = dispatchStartX;
dispatchEndY = dispatchStartY;
return super.dispatchTouchEvent(ev);
}
int InterceptEndX;
int InterceptEndY;
boolean intercept;
@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
int dispatchStartX = (int) ev.getX();
int dispatchStartY = (int) ev.getY();
switch (ev.getAction()) {
case MotionEvent.ACTION_DOWN:
intercept = false;
break;
case MotionEvent.ACTION_MOVE:
int deltax = InterceptEndX - dispatchStartX;
int deltaY = InterceptEndY - dispatchStartY;
if (Math.abs(deltaY) <= Math.abs(deltax) - 10) {
startX = 0;
lastX = 0;
intercept = true;
} else {
intercept = false;
}
break;
case MotionEvent.ACTION_UP:
intercept = false;
break;
}
InterceptEndX = dispatchStartX;
InterceptEndY = dispatchStartY;
return intercept;
}
private class AutoScllorRunnable implements Runnable {
int currentTotalx;
int totalXValue;
public AutoScllorRunnable(int currentTotalx) {
this.currentTotalx = currentTotalx;
totalXValue = (currentTotalx - totalX) / 10;
}
@Override
public void run() {
if (scllorTime > 0) {
totalX = totalX + totalXValue;
scllorTime--;
scroll();
HorizontalScrollView.this.postDelayed(this, 1);
}
}
}
}