廢話就不多說了，開始今天的正題，帶你實現開發者頭條APP的啟動頁。
一.老規矩，先上效果圖
從效果圖中我們可以看出，整個滑動的界面就是一個ViewPager實現，然后監聽ViewPager的滑動事件，改變底部四個小圖標的切換，以及跳轉到首頁的按鈕的隱藏顯示。
二.代碼實現
1).整個布局文件。上面是ViewPager，下面是四個小圖標存放的容器。
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"xmlns:tools="http://schemas.android.com/tools"android:layout_width="match_parent"android:layout_height="match_parent"android:background="#FCF2E4"><android.support.v4.view.ViewPagerandroid:id="@+id/viewpager_launcher"android:layout_width="match_parent"android:layout_height="match_parent" /><RelativeLayoutandroid:layout_width="fill_parent"android:layout_height="wrap_content"android:orientation="vertical" ><LinearLayoutandroid:id="@+id/viewGroup"android:layout_width="fill_parent"android:layout_height="wrap_content"android:layout_alignParentBottom="true"android:layout_marginBottom="30dp"android:gravity="center_horizontal"android:orientation="horizontal"/></RelativeLayout></RelativeLayout>
2).LauncherActivity 首先判斷是否第一次啟動，如果不是第一次直接進入首頁，是第一次啟動就初始化ViewPager，設置適配器，設置ViewPager滑動監聽，然后添加底部的。。。View。 在Viewpager監聽函數里面改變底部圖標的選中狀態，如果是最后一頁顯示“開啟我的頭條”按鈕。
/*** 第一次啟動頁面* * @author Ansen* @create time 2016-04-15*/@SuppressLint("ResourceAsColor")public class LauncherActivity extends FragmentActivity implements ILauncherView {private ViewPager viewpagerLauncher;private LauncherPagerAdapter adapter;private ImageView[] tips;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_luancher);if(!isFirst()){gotoMain();}viewpagerLauncher = (ViewPager) findViewById(R.id.viewpager_launcher);adapter = new LauncherPagerAdapter(this, this);viewpagerLauncher.setOffscreenPageLimit(2);viewpagerLauncher.setCurrentItem(0);viewpagerLauncher.setOnPageChangeListener(changeListener);viewpagerLauncher.setAdapter(adapter);viewpagerLauncher.setOnPageChangeListener(changeListener);ViewGroup group = (ViewGroup) findViewById(R.id.viewGroup);// 初始化底部顯示控件tips = new ImageView[4];for (int i = 0; i < tips.length; i++) {ImageView imageView = new ImageView(this);if (i == 0) {imageView.setBackgroundResource(R.drawable.page_indicator_focused);} else {imageView.setBackgroundResource(R.drawable.page_indicator_unfocused);}tips[i] = imageView;LinearLayout.LayoutParams layoutParams = new LinearLayout.LayoutParams(new ViewGroup.LayoutParams(LayoutParams.WRAP_CONTENT,LayoutParams.WRAP_CONTENT));layoutParams.leftMargin = 10;// 設置點點點view的左邊距layoutParams.rightMargin = 10;// 設置點點點view的右邊距group.addView(imageView, layoutParams);}}private OnPageChangeListener changeListener = new OnPageChangeListener() {@Overridepublic void onPageScrollStateChanged(int arg0) {}@Overridepublic void onPageScrolled(int arg0, float arg1, int arg2) {}@Overridepublic void onPageSelected(int index) {setImageBackground(index);// 改變點點點的切換效果TextView tvStartHeadlines = (TextView) adapter.getViews().get(index).findViewById(R.id.tv_start_headlines);if (index == tips.length - 1) {// 最后一個tvStartHeadlines.setVisibility(View.VISIBLE);} else {tvStartHeadlines.setVisibility(View.INVISIBLE);}}};/*** 改變點點點的切換效果* @param selectItems*/private void setImageBackground(int selectItems) {for (int i = 0; i < tips.length; i++) {if (i == selectItems) {tips[i].setBackgroundResource(R.drawable.page_indicator_focused);} else {tips[i].setBackgroundResource(R.drawable.page_indicator_unfocused);}}}@Overridepublic void gotoMain() {Intent intent = new Intent(this, MainActivity.class);startActivity(intent);finish();}private boolean isFirst() {SharedPreferences setting = getSharedPreferences("headlines", 0);Boolean user_first = setting.getBoolean("FIRST", true);if (user_first) {// 第一次setting.edit().putBoolean("FIRST", false).commit();return true;} else {return false;}}}3).LauncherPagerAdapter 繼承PagerAdapter，在構造函數中初始化要顯示的所有頁面，其他的跟普通的適配器沒啥區別，就多了兩個重寫的方法，destroyItem跟instantiateItem。destroyItem是刪除一個頁面，instantiateItem是加載一個頁面。。
/*** ViewPager適配器* @author ansen* @create time 2016-04-15*/public class LauncherPagerAdapter extends PagerAdapter implements OnClickListener{private ILauncherView launcherView;private List<View> views;//每頁顯示的圖片private int[] images=new int[]{R.drawable.tutorial_1,R.drawable.tutorial_2,R.drawable.tutorial_3,R.drawable.tutorial_4};public LauncherPagerAdapter(Context context,ILauncherView launcherView){views=new ArrayList<View>();this.launcherView=launcherView;//初始化每頁顯示的Viewfor(int i=0;i<images.length;i++){View item=LayoutInflater.from(context).inflate(R.layout.activity_luancher_pager_item, null);ImageView imageview=(ImageView) item.findViewById(R.id.imageview);imageview.setImageResource(images[i]);item.findViewById(R.id.tv_start_headlines).setOnClickListener(this);views.add(item);}}public List<View> getViews() {return views;}@Overridepublic int getCount() {return views == null ? 0 : views.size();}@Overridepublic boolean isViewFromObject(View arg0, Object arg1) {return arg0==arg1;}@Overridepublic void destroyItem(ViewGroup container, int position, Object object){((ViewPager) container).removeView(views.get(position));}@Overridepublic Object instantiateItem(ViewGroup container, int position) {((ViewPager) container).addView(views.get(position), 0);return views.get(position);}@Overridepublic void onClick(View v) {launcherView.gotoMain();}}4).還有每一頁顯示的item布局，以及“開啟我的頭條”按鈕的背景shape我就不一一貼出來了。
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