viewpager滑动实现二次跳转页面

布局


<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

     <android.support.v4.view.ViewPager
         android:id="@+id/viewpager"
         android:layout_width="match_parent"
         android:layout_height="match_parent"/>

    <Button
        android:id="@+id/btn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="跳转"
        android:visibility="gone"
        android:layout_alignParentBottom="true"
        android:layout_marginLeft="150dp"
        />

</RelativeLayout>

主函数
package com.example.rikao20;

import android.content.Intent;
import android.content.SharedPreferences;
import android.support.annotation.NonNull;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.ImageView;

import java.util.ArrayList;

public class MainActivity extends AppCompatActivity {

private ViewPager viewpager;
private Button btn;
ArrayList<Integer> list;
SharedPreferences sharedPreferences;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    list = new ArrayList<>();
    btn = findViewById(R.id.btn);
    viewpager = findViewById(R.id.viewpager);


    list.add(R.drawable.splash01);
    list.add(R.drawable.splash02);
    list.add(R.drawable.splash03);
    list.add(R.drawable.splash04);


    sharedPreferences = getSharedPreferences("bu",MODE_PRIVATE);
    boolean isZD = sharedPreferences.getBoolean("isZD",false);
    viewpager.setAdapter(new Myadapter());
    if(isZD){
        Intent intent = new Intent(MainActivity.this,SendActivity.class);

        startActivity(intent);
        finish();
    }



    viewpager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
        @Override
        public void onPageScrolled(int i, float v, int i1) {

        }

        @Override
        public void onPageSelected(int i) {

            switch (i){
                case 0:
                    btn.setVisibility(View.GONE);
                    break;
                case 1:
                    btn.setVisibility(View.GONE);
                    break;
                case 2:
                    btn.setVisibility(View.GONE);
                    break;
                case 3:
                    btn.setVisibility(View.VISIBLE);
                    break;
            }
        }
        @Override
        public void onPageScrollStateChanged(int i) {
        }
    });
    btn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            SharedPreferences.Editor editor = sharedPreferences.edit();
            editor.putBoolean("isZD",true);
            editor.commit();

            Intent intent = new Intent(MainActivity.this,SendActivity.class);

            startActivity(intent);
            finish();
        }
    });



}
class Myadapter extends PagerAdapter {

    @Override
    public int getCount() {
        return list.size();
    }

    @Override
    public boolean isViewFromObject(@NonNull View view, @NonNull Object o) {

        return view == o;
    }

    @NonNull
    @Override
    public Object instantiateItem(@NonNull ViewGroup container, int position) {
        ImageView imageView = new ImageView(MainActivity.this);
        imageView.setScaleType(ImageView.ScaleType.FIT_XY);
        imageView.setImageResource(list.get(position));
        container.addView(imageView);
        return imageView;
    }


    @Override
    public void destroyItem(@NonNull ViewGroup container, int position, @NonNull Object object) {
        container.removeView((View) object);

    }
}

}