Android ViewPager无限循环实现底部小圆点动态滑动
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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