三行代码实现一个轮播 BannerView
qnda5002
8年前
<p>自己简单封装了一个带hint的轮播ViewPager,用来展示app首页的Banner,先看效果图吧。</p> <p style="text-align:center"><img src="https://simg.open-open.com/show/3b9fb502cd3b56b031d184ac200defd1.gif"></p> <p>使用起来非常方便~~2至3行代码就能实现上述效果,只要传入一个list就可以(其中是你需要展示的ImageView),当然也可以自己在这基础上添加各种Transform动画。</p> <pre> <code class="language-java">bannerView = (BannerView) findViewById(R.id.banner); bannerView.setViewList(viewList); bannerView.startLoop(true);</code></pre> <p>实现原理相信大家应该都知道,就是可能懒得去封装这种东西。</p> <p>具体思路:</p> <ul> <li> <ol> <li>继承自FrameLayout,在下层填充一个ViewPager</li> </ol> </li> <li> <p>2.根据ViewPager的itemCount去动态生成底部hint小圆点</p> </li> </ul> <pre> <code class="language-java">if (mLinearPosition.getChildCount() != viewSize) { int diffCnt = mLinearPosition.getChildCount() - viewSize; boolean needAdd = diffCnt < 0; diffCnt = Math.abs(diffCnt); for (int i = 0; i < diffCnt; i++) { if (needAdd) { ImageView img = new ImageView(getContext()); LinearLayout.LayoutParams layoutParams = new LinearLayout.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT); layoutParams.rightMargin = getResources().getDimensionPixelOffset(R.dimen.dimen_9dp); img.setLayoutParams(layoutParams); img.setBackgroundResource(R.drawable.banner_point); mLinearPosition.addView(img); } else { mLinearPosition.removeViewAt(0); } } }</code></pre> <ul> <li>3.通过Handler去控制轮播的频率,重新设置ViewPager的currentItem以及hint小圆点的背景</li> </ul> <pre> <code class="language-java">private static class BannerHandler extends Handler { private WeakReference<BannerView> weakReference = null; public BannerHandler(BannerView bannerView) { super(Looper.getMainLooper()); this.weakReference = new WeakReference<BannerView>(bannerView); } @Override public void handleMessage(Message msg) { super.handleMessage(msg); if (this.weakReference == null) { return; } BannerView bannerView = this.weakReference.get(); if (bannerView == null || bannerView.mViewPager == null || bannerView.mViewPager.getAdapter() == null || bannerView.mViewPager.getAdapter().getCount() <= 0) { sendEmptyMessageDelayed(MSG_LOOP, LOOP_INTERVAL); return; } int curPos = bannerView.mViewPager.getCurrentItem(); curPos = (curPos + 1) % bannerView.mViewPager.getAdapter().getCount(); bannerView.mViewPager.setCurrentItem(curPos); sendEmptyMessageDelayed(MSG_LOOP, LOOP_INTERVAL); } }</code></pre> <ul> <li>4.具体细节,如无限轮播adapter的创建,handler中的弱引用,启动销毁loop等等</li> </ul> <p> </p> <p> </p> <p>项目主页:<a href="http://www.open-open.com/lib/view/home/1490082409129">http://www.open-open.com/lib/view/home/1490082409129</a></p> <p> </p>