时间：2022-01-13 09:41:50 | 栏目：Android代码 | 点击：次
在项目中用到了Android的ViewPager组件，但是发现在滑动的时候不是特别流畅，有些小的滑动无法响应，于是考虑进行优化。
ViewPager 手指滑动切换时会不灵敏，我们查看ViewPager源码，切换的判断是由mFlingDistance和mMinimumVelocity决定的。
private int determineTargetPage(int currentPage, float pageOffset, int velocity, int deltaX) {
int targetPage;
if (Math.abs(deltaX) > mFlingDistance && Math.abs(velocity) > mMinimumVelocity) {
targetPage = velocity > 0 ? currentPage : currentPage + 1;
} else {
final float truncator = currentPage >= mCurItem ? 0.4f : 0.6f;
targetPage = currentPage + (int) (pageOffset + truncator);
}
......
而mFlingDistance和mMinimumVelocity是类内部计算的，并没有公开接口提供设置。
private static final int MIN_DISTANCE_FOR_FLING = 25; // dips
private static final int MIN_FLING_VELOCITY = 400; // dips
void initViewPager() {
mMinimumVelocity = (int) (MIN_FLING_VELOCITY * density);
mFlingDistance = (int) (MIN_DISTANCE_FOR_FLING * density
}
我们可以通过反射来调整这2个值，解决滑动灵敏度的问题
val mFlingDistance: Field
mFlingDistance = ViewPager::class.java.getDeclaredField("mFlingDistance")
mFlingDistance.setAccessible(true)
val distance = mFlingDistance.get(mViewPager)//获取值
mFlingDistance.set(mViewPager, 10) //你定义的值
val mMinimumVelocity: Field
mMinimumVelocity = ViewPager::class.java.getDeclaredField("mFlingDistance")
mMinimumVelocity.setAccessible(true)
val velocity = mMinimumVelocity.get(mViewPager)//获取值
mMinimumVelocity.set(mViewPager, 5)//你定义的值