前言
这次要在上一篇轮播图的基础上做改造，增加两个功能：
- 用户触摸到轮播图时，停止轮播
- 在轮播图上展示一个小指示器，指示当前轮播组件的位置
触摸停播
触摸停播的设计思路是：监听实现轮播图的触摸事件，如果用户正在触摸就停止自动轮播。
package com.example.loopapplication.looper;import android.content.Context;
import android.util.AttributeSet;
import android.view.MotionEvent;import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.viewpager.widget.ViewPager;public class TouchableViewPager extends ViewPager {OnViewPagerTouchListener mOnViewPagerTouchListener;public TouchableViewPager(@NonNull Context context) {super(context);}public TouchableViewPager(@NonNull Context context, @Nullable AttributeSet attrs) {super(context, attrs);}@Overridepublic boolean onTouchEvent(MotionEvent ev) {switch (ev.getAction()) {case MotionEvent.ACTION_DOWN:// 触摸开始if (mOnViewPagerTouchListener != null) {mOnViewPagerTouchListener.onPageTouched(true);}break;case MotionEvent.ACTION_CANCEL:case MotionEvent.ACTION_UP:// 触摸结束if (mOnViewPagerTouchListener != null) {mOnViewPagerTouchListener.onPageTouched(false);}break;}return super.onTouchEvent(ev);}public void setOnTouchListener(TouchableViewPager.OnViewPagerTouchListener listener) {mOnViewPagerTouchListener = listener;}public interface OnViewPagerTouchListener{void onPageTouched(boolean isTouched);}
}
mViewPager.setOnTouchListener(new TouchableViewPager.OnViewPagerTouchListener() {@Overridepublic void onPageTouched(boolean isTouched) {mIsTouch = isTouched;}}); private Runnable mLoopTask = new Runnable() {@Overridepublic void run() {if (!mIsTouch) {int currentItems = mViewPager.getCurrentItem();// 将当前组件序号自增，达到自动轮播的效果mViewPager.setCurrentItem(++currentItems);}// 自动轮播间隔1秒mHandler.postDelayed(this, 2000);}};
指示器
指示器的设计思路是：
轮播图初始化时，创建数据个数相等的小圆点，默认为未选中状态。
监听轮播图切换轮播视图事件，每次组件切换都遍历一次圆点，将对应当前数据位置的圆点改成选中态。
/*** 初始化圆点阵列*/private void initPointIndication() {mPointIndication = this.findViewById(R.id.point_indication);for (int i = 0; i < mPictures.size(); i++) {View viewPoint = new View(this);LinearLayout.LayoutParams layoutParams = new LinearLayout.LayoutParams(ViewUtils.dp2dx(this, 15), ViewUtils.dp2dx(this, 15));layoutParams.leftMargin = ViewUtils.dp2dx(this, 10);viewPoint.setLayoutParams(layoutParams);viewPoint.setBackground(getResources().getDrawable(R.drawable.shape_point_normal));mPointIndication.addView(viewPoint);}}/*** 设置圆点选中态* @param curPosition*/private void setPointIndication(int curPosition) {if (mPointIndication != null) {for (int i = 0; i < mPointIndication.getChildCount(); i++) {View point = mPointIndication.getChildAt(i);if (point != null) {if (i == curPosition) {Log.d(TAG, "setPointIndication: 选中 " + i);point.setBackground(getResources().getDrawable(R.drawable.shape_point_selected));} else {point.setBackground(getResources().getDrawable(R.drawable.shape_point_normal));}}}}} mViewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {@Overridepublic void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {}@Overridepublic void onPageSelected(int position) {// 轮播当前展示的位置 需要换算成数据里面的真实位置int realPosition = 0;if (mLooperPagerAdapter.getDataSize() != 0) {realPosition = position % mLooperPagerAdapter.getDataSize();}Log.d(TAG, "onPageSelected: position = " + position + ", real position = " + realPosition + ", data size = " + mLooperPagerAdapter.getDataSize());setPointIndication(realPosition);}@Overridepublic void onPageScrollStateChanged(int state) {}});
)
