Android基础：ViewPage

介绍

        ViewPage主要是实现左右切换当前的view，实现滑动切换的效果。

实现代码

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

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

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

public class MainActivity extends AppCompatActivity {

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

        // 渲染布局
        LayoutInflater layoutInflater = getLayoutInflater().from(this);
        View view = layoutInflater.inflate(R.layout.unread_layout,null);
        View view2 = layoutInflater.inflate(R.layout.read_layout,null);
        View view3 = layoutInflater.inflate(R.layout.read_layout,null);
        List<View> viewList = new ArrayList<>();
        viewList.add(view);
        viewList.add(view2);
        viewList.add(view3);

        ViewPager viewPager = findViewById(R.id.view_page1);
        MyAdapter myAdapter = new MyAdapter(viewList);
        viewPager.setAdapter(myAdapter);

    }
}

import java.util.List;

public class MyAdapter extends PagerAdapter {
    private List<View> viewList;

    public MyAdapter(List<View> viewList){
        this.viewList = viewList;
    }
    @Override
    public int getCount() {
        return viewList == null ? 0 : viewList.size();
    }


    /**
     * 将给定位置的View 添加到ViewGroup中，并显示出来
     * 返回一个代表新页面的Object(key)，通常都是返回view本身就行
     *
     * @param container container
     * @param position position
     * @return view
     */
    @NonNull
    @Override
    public Object instantiateItem(@NonNull ViewGroup container, int position) {
        container.addView(viewList.get(position),0);
        return viewList.get(position);
    }

    /**
     * 判断instantiateItem()方法返回的key是否跟一个页面视图是否相同
     * @param view
     * @param object
     * @return
     */
    @Override
    public boolean isViewFromObject(@NonNull View view, @NonNull Object object) {
        return view == object;
    }

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

<!-- activity_main.xml -->
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
    android:orientation="vertical"
    tools:context=".MainActivity">


    <androidx.viewpager.widget.ViewPager
        android:id="@+id/view_page1"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        />
</LinearLayout>

<!-- unread_layout.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"
    android:gravity="center"
    android:orientation="vertical">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="未阅读信息"
        android:textSize="36sp"
        />

</LinearLayout>

<!-- read_layout.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"
    android:gravity="center"
    android:orientation="vertical">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="已阅读信息"
        android:textSize="36sp"
        />

</LinearLayout>

<!-- all_layout.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"
    android:gravity="center"
    android:orientation="vertical">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="全部信息"
        android:textSize="36sp"
        />

</LinearLayout>