ViewPager引導頁，底部圓點導航

專案串列

首先新建一個class檔案，名字為 MyPageAdapter.java

package com.example.smartwee;

import android.content.Context;
import android.view.View;
import android.view.ViewGroup;

import androidx.annotation.NonNull;
import androidx.viewpager.widget.PagerAdapter;

import java.util.List;

public class MyPageAdapter extends PagerAdapter {
    private List<View> views;
    private Context context;
    MyPageAdapter(List<View> views,Context context){
        this.context=context;
        this.views=views;
    }
    @Override
    public int getCount() {
        return views.size();
    }

    @Override
    public boolean isViewFromObject(@NonNull View view, @NonNull Object object) {
        return view == object;
    }
    @NonNull
    @Override
    public Object instantiateItem(@NonNull ViewGroup container, int position) {
        container.addView(views.get(position));
        return views.get(position);
    }

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

}

創建布局檔案，welcome_0,welcome_1welcome_2,welcome_3,welcome_4,

一共五個，代表有五頁的引導，可以增加或減少，不過Welcom.java中的代碼也需要更改

布局代碼都是一樣的，這里貼一個，使用scaleType讓圖片按比例填充，多余的裁剪

<?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"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <ImageView
        android:id="@+id/imageView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/bg_lz2"
        android:scaleType="centerCrop"/>
</RelativeLayout>

新建一個Activity，名字為 Welcome

package com.example.smartwee;

import androidx.appcompat.app.AppCompatActivity;
import androidx.viewpager.widget.ViewPager;

import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.ImageView;

import java.util.ArrayList;
import java.util.List;

public class Welcome extends AppCompatActivity {

    private ViewPager viewPager;
    private ImageView iv1,iv2,iv3,iv4,iv5;
    private int[] pics={R.layout.welcome_0,R.layout.welcome_1,R.layout.welcome_2,R.layout.welcome_3,R.layout.welcome_4};
    private List<View> views;
    private MyPageAdapter pageAdapter;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_welcome);
        //獲取控制元件
        iv1 =findViewById(R.id.iv_1);
        iv2 =findViewById(R.id.iv_2);
        iv3 =findViewById(R.id.iv_3);
        iv4 =findViewById(R.id.iv_4);
        iv5 =findViewById(R.id.iv_5);
        viewPager=findViewById(R.id.viewPager);
        initView();
    }

    private void initView() {
        //初始化圓點，讓第一個點為true，其他的關閉
        setDot(true,false,false,false,false);


        if (views == null)
            views = new ArrayList<>();//判斷初始化
        for (int i =0;i < pics.length;i++){
            View view = LayoutInflater.from(this).inflate(pics[i],null);
            views.add(view);//將pics中的布局添加至view中
        }
        pageAdapter = new MyPageAdapter(views,this);//MyPageAdapter是開始時創建的名字，可以自己更改
        viewPager.setAdapter(pageAdapter);//設定配接器

        //給viewpage添加監聽事件
        viewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
            @Override
            public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

            }

            @Override
            public void onPageSelected(int position) {//position的值代表你翻動到了第幾頁

                switch (position){
                    case 0:
                        setDot(true,false,false,false,false);
                        break;
                    case 1:
                        setDot(false,true,false,false,false);
                        break;
                    case 2:
                        setDot(false,false,true,false,false);
                        break;
                    case 3:
                        setDot(false,false,false,true,false);
                        break;
                    case 4:
                        setDot(false,false,false,false,true);
                        break;
                }
            }

            @Override
            public void onPageScrollStateChanged(int state) {

            }
        });
    }

    private void setDot(boolean a,boolean b,boolean c,boolean d,boolean e) {
        if (a){
            iv1.setImageResource(R.drawable.btn_select_t_12);
        }else {
            iv1.setImageResource(R.drawable.btn_select_f_12);
        } if (b){
            iv2.setImageResource(R.drawable.btn_select_t_12);
        }else {
            iv2.setImageResource(R.drawable.btn_select_f_12);
        } if (c){
            iv3.setImageResource(R.drawable.btn_select_t_12);
        }else {
            iv3.setImageResource(R.drawable.btn_select_f_12);
        } if (d){
            iv4.setImageResource(R.drawable.btn_select_t_12);
        }else {
            iv4.setImageResource(R.drawable.btn_select_f_12);
        } if (e){
            iv5.setImageResource(R.drawable.btn_select_t_12);
        }else {
            iv5.setImageResource(R.drawable.btn_select_f_12);
        }//圖片t_12是一個12像素的綠點，我用ps畫的，f_12是白色的
    }

}

啟動前不要忘記在AndroidManifest.xml中更改啟動頁

啟動效果：