4/24 学习总结

今天学习了制作轮播图效果，实现了最基础的版本：单击实现轮播且不能无线滑动，即划到最后一张再点击就没有效果了

实现原理：与向listview中添加数据有很大相似之处

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    xmlns:tools="http://schemas.android.com/tools"
    tools:content=".MainActivity">

    <androidx.viewpager.widget.ViewPager
        android:id="@+id/im1"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:scaleType="fitXY"/>


</RelativeLayout>

item,xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
<ImageView
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/im2"/>
</LinearLayout>

Activity.java

package com.example.myapplication23;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.viewpager.widget.PagerAdapter;
import androidx.viewpager.widget.ViewPager;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.drawable.BitmapDrawable;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;

import com.handmark.pulltorefresh.library.PullToRefreshBase;
import com.handmark.pulltorefresh.library.PullToRefreshListView;

import java.util.ArrayList;
import java.util.List;
import java.util.Timer;
import java.util.TimerTask;

public class MainActivity extends AppCompatActivity {
    private ViewPager viewPager;
   private List<Integer>list=new ArrayList<>();




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

    private void initViews() {  //加载布局

        viewPager = (ViewPager) findViewById(R.id.im1);
        viewPager.setAdapter(my);
    }

    private PagerAdapter my=new PagerAdapter(){

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

        @Override
        public boolean isViewFromObject(@NonNull View view, @NonNull Object object) {
            return view==object;
        }
        //Alt+Insert
        @NonNull
        @Override
        public Object instantiateItem(@NonNull ViewGroup container, int position) {
           View item= LayoutInflater.from(container.getContext()).inflate(R.layout.item,container,false);
           ImageView iv=item.findViewById(R.id.im2);
           //设置数据

            iv.setImageResource(list.get(position));
            if(iv.getParent() instanceof ViewGroup){
                ((ViewGroup)iv.getParent()).removeView(iv);
            }
            container.addView(iv);
           return iv;
        }

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




    private void initData() {    //加载数据
        list.add(R.mipmap.a1);
        list.add(R.mipmap.a2);
        list.add(R.mipmap.a3);
        my.notifyDataSetChanged();
    }
}