详解Android App中创建ViewPager组件的方法

2020-01-02 06:59:04

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现在很多app一打开就是一个ViewPager，然后可以用手指滑，每滑一次就换一张图，底下还会有圈圈表示说现在滑到第几章~
通常这些图片都是放功能简介或是使用教学之类的，我的需求很简单，就是上面提到的那样而已。
有两种做法，一种是找现有套件，查了一堆资料每个都跟我推荐ViewPagerIndicator这套，我之前也看过这套，只是看起来需要有fragment再加上google play范例好像载不到了，所以只好自己实做一个。
Viewpager的实作可参考Android ViewPager使用详解里面的程序码:

@Overrideprotected void onCreate(Bundle savedInstanceState) {  super.onCreate(savedInstanceState);  setContentView(R.layout.activity_intro);  mViewPager = (ViewPager) findViewById(R.id.viewpager);  final LayoutInflater mInflater = getLayoutInflater().from(this);  View v1 = mInflater.inflate(R.layout.intro_layout_1, null);  View v2 = mInflater.inflate(R.layout.intro_layout_2, null);  View v3 = mInflater.inflate(R.layout.intro_layout_3, null);  View v4 = mInflater.inflate(R.layout.intro_layout_4, null);  viewList = new ArrayList<View>();  viewList.add(v1);  viewList.add(v2);  viewList.add(v3);  viewList.add(v4);  mViewPager.setAdapter(new MyViewPagerAdapter(viewList));  mViewPager.setCurrentItem(0);}MyViewPagerAdapterpublic class MyViewPagerAdapter extends PagerAdapter {  private List<View> mListViews;  public MyViewPagerAdapter(List<View> mListViews) {    this.mListViews = mListViews;  }  @Override  public void destroyItem(ViewGroup container, int position, Object object)  {    container.removeView((View) object);  }  @Override  public Object instantiateItem(ViewGroup container, int position) {    View view = mListViews.get(position);    container.addView(view);    return view;  }  @Override  public int getCount() {    return mListViews.size();  }  @Override  public boolean isViewFromObject(View arg0, Object arg1) {    return arg0==arg1;  }}

这样子你就有一个ViewPager了

下面我们来具体看一下ViewPager的用法：
一、ViewPager创建步骤
① 在XML布局中加入android.support.v4.view.ViewPager

② 加载显示的页卡将Layout布局转换为View对象

(1)

LayoutInflater lf getLayoutInflater().from(this);  lf.inflate(resource,root);

(2)

View.inflate(context,resource,root);

③ 配置Adapter（三种Adapter）

(1)PagerAdapter 数据源：List<View>
(2)FragmentPagerAdapter 数据源：List<Fragment>
(3)FragmentStatePagerAdapter 数据源：List<Fragment>
二、代码示例
新建四个Fragment和他们的布局下面是MainActivity的xml布局：

<android.support.v4.view.ViewPager    android:id="@+id/pager"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:layout_gravity="center" >    <android.support.v4.view.PagerTabStrip      android:id="@+id/tab"      android:layout_width="wrap_content"      android:layout_height="wrap_content"      android:layout_gravity="top" >    </android.support.v4.view.PagerTabStrip>    <!-- 底部显示标题与上面的顶部显示不能同时出现    <android.support.v4.view.PagerTitleStrip      android:id="@+id/title"      android:layout_width="wrap_content"      android:layout_height="wrap_content"      android:layout_gravity="bottom" >    </android.support.v4.view.PagerTitleStrip>    -->  </android.support.v4.view.ViewPager>

第一种PagerAdapter

public class MyPagerAdapter extends PagerAdapter {  private List<View> viewList;  private List<String> titleList;  public MyPagerAdapter(List<View> viewList,List<String> titleList){    this.viewList = viewList;    this.titleList = titleList;  }  /**   * 返回页卡的数量   */  @Override  public int getCount() {    return viewList.size();  }   /**   * view是否来自对象   */  @Override  public boolean isViewFromObject(View arg0, Object arg1) {    return arg0==arg1;  }   /**   * 实例化一个页卡   */  @Override  public Object instantiateItem(ViewGroup container, int position) {    container.addView(viewList.get(position));    return viewList.get(position);  }   /**   * 销毁一个页卡   */  @Override  public void destroyItem(ViewGroup container, int position, Object object) {    container.removeView(viewList.get(position));  }  /**   * 设置ViewPager的标题   */  @Override  public CharSequence getPageTitle(int position) {    return titleList.get(position);  }}

第二种FragmentPagerAdapter

public class MyFragmentPagerAdapter extends FragmentPagerAdapter {  private List<Fragment> fragList;  private List<String> titleList;  public MyFragmentPagerAdapter(FragmentManager fm,List<Fragment> fragList,List<String> titleList) {    super(fm);    this.fragList = fragList;    this.titleList = titleList;  }  @Override  public Fragment getItem(int arg0) {    return fragList.get(arg0);  }  @Override  public CharSequence getPageTitle(int position) {    return titleList.get(position);  }  @Override  public int getCount() {    return fragList.size();  }}

第三种FragmentStatePagerAdapter（该适配器可以动态销毁Fragment）

public class MyFragmentPagerAdapter2 extends FragmentStatePagerAdapter {//该适配器可以动态销毁  private List<Fragment> fragList;  private List<String> titleList;  public MyFragmentPagerAdapter2(FragmentManager fm,List<Fragment> fragList,List<String> titleList) {    super(fm);    this.fragList = fragList;    this.titleList = titleList;  }  @Override  public Fragment getItem(int arg0) {    return fragList.get(arg0);  }  @Override  public CharSequence getPageTitle(int position) {    return titleList.get(position);  }  @Override  public int getCount() {    return fragList.size();  }  @Override  public Object instantiateItem(ViewGroup arg0, int arg1) {    return super.instantiateItem(arg0, arg1);  }  @Override  public void destroyItem(ViewGroup container, int position, Object object) {    super.destroyItem(container, position, object);  }}

MainActivity里使用getSupportFragmentManager()该Activity必须继承FragmentActivity：

public class MainActivity extends FragmentActivity implements OnPageChangeListener{  private List<View> viewList;  private List<String> titleList;  private ViewPager pager;  private PagerTabStrip tab;//顶部标题  private List<Fragment> fragList;  @Override  protected void onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);    setContentView(R.layout.activity_main);    viewList = new ArrayList<View>();    titleList = new ArrayList<String>();    tab = (PagerTabStrip) findViewById(R.id.tab);    View view1 = View.inflate(this,R.layout.view1,null);    View view2 = View.inflate(this,R.layout.view2,null);    View view3 = View.inflate(this,R.layout.view3,null);    View view4 = View.inflate(this,R.layout.view4,null);    viewList.add(view1);    viewList.add(view2);    viewList.add(view3);    viewList.add(view4);    fragList = new ArrayList<Fragment>();    fragList.add(new Fragment1());    fragList.add(new Fragment2());    fragList.add(new Fragment3());    fragList.add(new Fragment4());    //为ViewPager页卡设置标题    titleList.add("第一页");    titleList.add("第二页");    titleList.add("第三页");    titleList.add("第四页");    //为PagerTabStrip设置一些属性    tab.setBackgroundColor(Color.WHITE);    tab.setDrawFullUnderline(false);    tab.setTabIndicatorColor(Color.BLUE);    pager = (ViewPager) findViewById(R.id.pager);    //MyPagerAdapter adapter = new MyPagerAdapter(viewList,titleList);    //MyFragmentPagerAdapter adapter = new MyFragmentPagerAdapter(getSupportFragmentManager(), fragList, titleList);    /**     * 使用getSupportFragmentManager()该Activity必须继承FragmentActivity     */    MyFragmentPagerAdapter2 adapter = new MyFragmentPagerAdapter2(getSupportFragmentManager(), fragList, titleList);    pager.setAdapter(adapter);    pager.setOnPageChangeListener(this);  }  @Override  public void onPageScrollStateChanged(int arg0) {  }  @Override  public void onPageScrolled(int arg0, float arg1, int arg2) {  }  @Override  public void onPageSelected(int arg0) {    Toast.makeText(this,"当前是第"+(arg0+1)+"个界面", 0).show();  }}

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