Android开发之轮播图广告的实现

package com.fly.lsn29_scrollimag; import java.util.ArrayList; import android.app.Activity; import android.os.Bundle; import android.support.v4.view.PagerAdapter; import android.support.v4.view.ViewPager; import android.support.v4.view.ViewPager.OnPageChangeListener; import android.view.View; import android.view.ViewGroup; import android.widget.ImageView; import android.widget.LinearLayout; import android.widget.LinearLayout.LayoutParams; import android.widget.RelativeLayout; import android.widget.TextView; public class MainActivity extends Activity implements OnPageChangeListener { private ViewPager viewPager; private int[] imageResIds; private ArrayList<ImageView> imageViewList; private LinearLayout ll_point_container; private String[] contentDescs; private TextView tv_desc; private int previousSelectedPosition = 0; boolean isRunning = false; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); // 初始化布局 View视图 initViews(); // Model数据 initData(); // Controller 控制器 initAdapter(); // 开启轮询 new Thread() { public void run() { isRunning = true; while (isRunning) { try { Thread.sleep(2000); } catch (InterruptedException e) { e.printStackTrace(); } // 往下跳一位 runOnUiThread(new Runnable() { @Override public void run() { System.out.println("设置当前位置: " + viewPager.getCurrentItem()); viewPager.setCurrentItem(viewPager.getCurrentItem() + 1); } }); } } ; }.start(); } @Override protected void onDestroy() { super.onDestroy(); isRunning = false; } private void initViews() { viewPager = (ViewPager) findViewById(R.id.viewpager); viewPager.setOnPageChangeListener(this);// 设置页面更新监听 // viewPager.setOffscreenPageLimit(1);// 左右各保留几个对象 ll_point_container = (LinearLayout) findViewById(R.id.ll_point_container); tv_desc = (TextView) findViewById(R.id.tv_desc); } private void initData() { // 初始化要显示的数据 // 图片资源id数组 imageResIds = new int[]{R.drawable.img01, R.drawable.img02, R.drawable.img03, R.drawable.img04, R.drawable.img05}; // 文本描述 contentDescs = new String[]{ "红米手机4x", "小米手机6", "小米手机6白色", "小米手机6黑色", "苹果手机" }; // 初始化要展示的5个ImageView imageViewList = new ArrayList<ImageView>(); ImageView imageView; View pointView; LayoutParams layoutParams; for (int i = 0; i < imageResIds.length; i++) { // 初始化要显示的图片对象 imageView = new ImageView(this); imageView.setBackgroundResource(imageResIds[i]); imageViewList.add(imageView); // 加小白点, 指示器 pointView = new View(this); pointView.setBackgroundResource(R.drawable.selector_bg_point); layoutParams = new LayoutParams(5, 5); if (i != 0) layoutParams.leftMargin = 10; // 设置默认所有都不可用 pointView.setEnabled(false); ll_point_container.addView(pointView, layoutParams); } } private void initAdapter() { ll_point_container.getChildAt(0).setEnabled(true); tv_desc.setText(contentDescs[0]); previousSelectedPosition = 0; // 设置适配器 viewPager.setAdapter(new MyAdapter()); // 默认设置到中间的某个位置 int pos = Integer.MAX_VALUE / 2 - (Integer.MAX_VALUE / 2 % imageViewList.size()); // 2147483647 / 2 = 1073741823 - (1073741823 % 5) viewPager.setCurrentItem(5000000); // 设置到某个位置 } class MyAdapter extends PagerAdapter { @Override public int getCount() { return Integer.MAX_VALUE; } // 3. 指定复用的判断逻辑, 固定写法 @Override public boolean isViewFromObject(View view, Object object) { // System.out.println("isViewFromObject: "+(view == object)); // 当划到新的条目, 又返回来, view是否可以被复用. // 返回判断规则 return view == object; } // 1. 返回要显示的条目内容, 创建条目 @Override public Object instantiateItem(ViewGroup container, int position) { System.out.println("instantiateItem初始化: " + position); // container: 容器: ViewPager // position: 当前要显示条目的位置 0 -> 4 // newPosition = position % 5 int newPosition = position % imageViewList.size(); ImageView imageView = imageViewList.get(newPosition); // a. 把View对象添加到container中 container.addView(imageView); // b. 把View对象返回给框架, 适配器 return imageView; // 必须重写, 否则报异常 } // 2. 销毁条目 @Override public void destroyItem(ViewGroup container, int position, Object object) { // object 要销毁的对象 System.out.println("destroyItem销毁: " + position); container.removeView((View) object); } } @Override public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) { // 滚动时调用 } @Override public void onPageSelected(int position) { // 新的条目被选中时调用 System.out.println("onPageSelected: " + position); int newPosition = position % imageViewList.size(); //设置文本 tv_desc.setText(contentDescs[newPosition]); // for (int i = 0; i < ll_point_container.getChildCount(); i++) { // View childAt = ll_point_container.getChildAt(position); // childAt.setEnabled(position == i); // } // 把之前的禁用, 把最新的启用, 更新指示器 ll_point_container.getChildAt(previousSelectedPosition).setEnabled(false); ll_point_container.getChildAt(newPosition).setEnabled(true); // 记录之前的位置 previousSelectedPosition = newPosition; } @Override public void onPageScrollStateChanged(int state) { // 滚动状态变化时调用 } }