页面拖动到最后一页 再向下滑动回复到 第一页，第一页向前滑动回到 最后一页
同时，底部红色小圆点随着页面的滑动距离比例随时改变位置
布局：
<?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:paddingBottom="@dimen/activity_vertical_margin" android:paddingLeft="@dimen/activity_horizontal_margin" android:paddingRight="@dimen/activity_horizontal_margin" android:paddingTop="@dimen/activity_vertical_margin" tools:context="com.lian.viewpagertest.MainActivity"> <android.support.v4.view.ViewPager android:id="@+id/viewpager" android:layout_width="match_parent" android:layout_height="match_parent" > </android.support.v4.view.ViewPager> <TextView android:id="@+id/tv" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="内容" android:textSize="25sp" android:layout_alignParentBottom="true" android:layout_centerHorizontal="true" /> <RelativeLayout android:id="@+id/rl_bottom" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignParentBottom="true" android:layout_centerHorizontal="true" android:layout_marginBottom="45dip" > <LinearLayout android:id="@+id/ll_points" android:layout_width="wrap_content" android:layout_height="wrap_content" android:orientation="horizontal" > </LinearLayout> <View android:id="@+id/v_redpoint" android:layout_width="10dip" android:layout_height="10dip" android:background="@drawable/red_circle" /> </RelativeLayout> </RelativeLayout>
其中red_circle是用shape绘制的红色小圆点
最后的LinearLayout实际上是灰色小圆点的容器，在代码中根据数据的长度动态确定数目
代码：
package com.lian.viewpagertest; import android.os.Bundle; import android.support.v4.view.PagerAdapter; import android.support.v4.view.ViewPager; import android.support.v7.app.AppCompatActivity; import android.util.Log; import android.view.View; import android.view.ViewGroup; import android.view.ViewTreeObserver; import android.widget.ImageView; import android.widget.LinearLayout; import android.widget.RelativeLayout; import android.widget.TextView; import java.util.ArrayList; import java.util.List; public class MainActivity extends AppCompatActivity { private ViewPager mViewPager; private TextView mTextView; private LinearLayout mLinearLayout; private View mView; private List<ImageView> mDataList; private int diatance; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); initView(); initData(); initEvent(); } /** * 初始化数据 */ private void initData() { int[] sorce = new int[]{R.drawable.a,R.drawable.b,R.drawable.c,R.drawable.d,R.drawable.e}; mDataList = new ArrayList<ImageView>(); for (int i = 0;i < sorce.length;i ++){ ImageView img = new ImageView(getApplicationContext()); img.setImageResource(sorce[i]); mDataList.add(img); //添加底部灰点 View v = new View(getApplicationContext()); v.setBackgroundResource(R.drawable.gray_circle); //指定其大小 LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(20,20); if (i != 0) params.leftMargin = 20; v.setLayoutParams(params); mLinearLayout.addView(v); } mViewPager.setAdapter(new MyAdapter()); //设置每次加载时第一页在MAX_VALUE / 2 - Extra 页，造成用户无限轮播的错觉 int startPage = Integer.MAX_VALUE / 2; int extra = startPage % mDataList.size(); startPage = startPage - extra; mViewPager.setCurrentItem(startPage); } /** * ViewPager的容器 */ public class MyAdapter extends PagerAdapter{ @Override public int getCount() { //告诉容器我们的数据长度为Integer.MAX_VALUE，这样就可以一直滚动 return Integer.MAX_VALUE; } @Override public boolean isViewFromObject(View view, Object object) { return view == object; } @Override public Object instantiateItem(ViewGroup container, int position) { //若position超过mDataList.size()，会发生越界异常，所以这里每次超过size又从0开始计算位置 position = position % mDataList.size(); ImageView img = mDataList.get(position); container.addView(img); return img; } @Override public void destroyItem(ViewGroup container, int position, Object object) { position = position % mDataList.size(); container.removeView((View)object); // super.destroyItem(container, position, object); } } private void initEvent() { /** * 当底部红色小圆点加载完成时测出两个小灰点的距离，便于计算后面小红点动态移动的距离 */ mView.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() { @Override public void onGlobalLayout() { diatance = mLinearLayout.getChildAt(1).getLeft() - mLinearLayout.getChildAt(0).getLeft(); Log.d("两点间距",diatance + "测出来了"); } }); mViewPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() { @Override public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) { //测出页面滚动时小红点移动的距离，并通过setLayoutParams(params)不断更新其位置 position = position % mDataList.size(); float leftMargin = diatance * (position + positionOffset); RelativeLayout.LayoutParams params = (RelativeLayout.LayoutParams) mView.getLayoutParams(); params.leftMargin = Math.round(leftMargin); mView.setLayoutParams(params); Log.d("红点在这",leftMargin + ""); } @Override public void onPageSelected(int position) { } @Override public void onPageScrollStateChanged(int state) { } }); } private void initView() { setContentView(R.layout.activity_main); mViewPager = (ViewPager) findViewById(R.id.viewpager); mTextView = (TextView) findViewById(R.id.tv); mLinearLayout = (LinearLayout) findViewById(R.id.ll_points); mView = findViewById(R.id.v_redpoint); } }
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