// 惯性线程
class FlingThread extends Thread {
// 初始速度
private int velocity;
private static final float INFLEXION = 0.35f;
// 取得系统摩擦系数
private float mFlingFriction = ViewConfiguration.getScrollFriction();
private float mPhysicalCoeff;
private final float DECELERATION_RATE = (float) (Math.log(0.78) / Math.log(0.9));
// 计算出惯性总时间
private double mDuration;
// 刷新频率
private int timeInterval = 1000 / 60; // 单位MS
// 当前惯性耗时
private int spendTime;
public FlingThread(float velocityX) {
velocity = (int) velocityX;
final float ppi = context.getResources().getDisplayMetrics().density * 160.0f;
mPhysicalCoeff =
SensorManager.GRAVITY_EARTH // g (m/s^2)
* 39.37f // inch/meter
* ppi
* 0.84f; // look and feel tuning
}
@Override
public void run() {
isInertia = true;
boolean isEnable = false;
if (velocity != 0) {
mDuration = getSplineFlingDuration(velocity);
// 不断循环直到惯性时间到达或者用户点击屏幕中断滑动
while (mDuration >= spendTime && isInertia) {
// 每时间间隔内惯性滑动的距离
int space =
(int)
(velocity
+ (2 * spendTime / timeInterval + 1)
* -velocity
/ mDuration
* timeInterval
/ 2)
* timeInterval
/ 1000;
try {
if (axesData.size() > 1) {
int max = axesData.get(axesData.size() - 1).X;
int min = axesData.get(0).X;
int maxLimit = width - rightPadding - 20;
int minLimit = leftPadding + yTextWidth + 20;
if (min + space > minLimit) { // 滑动以后左边界判断
if (min < minLimit) {
isEnable = true;
} else {
space = 0;
refreshChart(space);
return;
}
} else {
isEnable = true;
}
if (max + space < maxLimit) { // 滑动后右边界判断
if (max > maxLimit) {
isEnable = true;
} else {
space = 0;
refreshChart(space);
return;
}
} else {
isEnable = true;
}
if (isEnable) {
refreshChart(space);
}
} else {
return;
}
spendTime += timeInterval;
sleep(timeInterval);
isScrollEnd = true;
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
// 根据速度计算加速度
private double getSplineDeceleration(int velocity) {
return Math.log(INFLEXION * Math.abs(velocity) / (mFlingFriction * 2 * mPhysicalCoeff));
}
/* Returns the duration, expressed in milliseconds */
private int getSplineFlingDuration(int velocity) {
final double l = getSplineDeceleration(velocity);
final double decelMinusOne = DECELERATION_RATE - 1.0;
return (int) (1000.0 * Math.exp(l / decelMinusOne));
}
}
