banner无限轮播

Posted 2020-08-08 嘉禾世兴

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">

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="200dp">

        <android.support.v4.view.ViewPager
            android:id="@+id/viewPager"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_alignParentLeft="true"
            android:layout_alignParentTop="true" />

        <LinearLayout
            android:id="@+id/dotLayout"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_alignParentBottom="true"
            android:layout_centerHorizontal="true"
            android:layout_marginBottom="20dp"
            android:gravity="center"
            android:orientation="horizontal" />

    </RelativeLayout>

</RelativeLayout>

 

selecter.xml

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:state_enabled="true">
        <shape android:shape="oval">
            <size android:height="10dp" android:width="10dp"></size>
            <solid android:color="#aa000000"></solid>
        </shape>
    </item>
    <item android:state_enabled="false">
        <shape android:shape="oval">
            <size android:height="10dp" android:width="10dp"></size>
            <solid android:color="#aaffffff"></solid>
        </shape>
    </item>
</selector>

 

public class MainActivity extends AppCompatActivity {

    private List<ImageView> list;
    private LinearLayout dotLayout;
    private int prePosition;
    private ViewPager viewPager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initData();
        initView();
        //开启一个新线程，实现ViewPager的自动滚动
        new Thread(new Runnable() {
            @Override
            public void run() {
                while (true) {
                    try {
                        Thread.sleep(3000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    //runOnUiThread中的代码运行在主线程中
                    runOnUiThread(new Runnable() {
                        @Override
                        public void run() {
                            viewPager.setCurrentItem(viewPager.getCurrentItem() + 1);
                        }
                    });
                }
            }
        }).start();
    }

    private void initView() {
        viewPager = (ViewPager) findViewById(R.id.viewPager);
        //构造适配器
        MyAdapter adapter = new MyAdapter(list);
        //设置Adapter
        viewPager.setAdapter(adapter);
        //设置ViewPager预加载的页数
//        viewPager.setOffscreenPageLimit(2);
        viewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
            //ViewPager滑动过程中调用
            @Override
            public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

            }

            //ViewPager新页面确定后调用
            @Override
            public void onPageSelected(int position) {
                //设置前一个View为白色
                dotLayout.getChildAt(prePosition).setEnabled(false);
                //设置当前View为红色
                dotLayout.getChildAt(position % list.size()).setEnabled(true);
                //将当前位置赋给prePosition
                prePosition = position % list.size();
            }

            //ViewPager滑动状态改变后调用
            //0--静止状态
            //1--手在拖动
            //2--手松开后自动滑动
            @Override
            public void onPageScrollStateChanged(int state) {

            }
        });
        //设置ViewPager的初始item
        viewPager.setCurrentItem(Integer.MAX_VALUE / 2 - 3);
    }

    /**
     * 构造数据源
     */
    private void initData() {
        dotLayout = (LinearLayout) findViewById(R.id.dotLayout);
        list = new ArrayList<>();
        int[] imgs = new int[]{R.drawable.a, R.drawable.b, R.drawable.c, R.drawable.d, R.drawable.e};
        for (int img : imgs) {
            //使用Java代码创建一个ImageView
            ImageView imageView = new ImageView(this);
            //设置图片以及ScaleType属性
            imageView.setImageResource(img);
            imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
            list.add(imageView);

            //创建一个View对象
            View view = new View(this);
            //设置View的宽和高
            LinearLayout.LayoutParams params = new LinearLayout.LayoutParams((int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 8, getResources().getDisplayMetrics()), (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 8, getResources().getDisplayMetrics()));
            //设置View左边距，避免View连在一起
            params.leftMargin = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 12, getResources().getDisplayMetrics());
            view.setLayoutParams(params);
            //设置背景颜色，背景使用selector，可使View在不同状态显示不同颜色
            view.setBackgroundResource(R.drawable.dot_radiobutton_style);
            //默认状态下View的Enable属性为false（View全为白色）
            view.setEnabled(false);
            //将View添加进LinearLayout中
            dotLayout.addView(view);
        }
        //第一个View默认为红色
        dotLayout.getChildAt(0).setEnabled(true);
    }

}