android_使用ViewPager和Fragment实现滑动导航

大家好，又见面了，我是全栈君。

ViewPage是android-support-v4.jar包提供的用于页面滑动的库.这里没有将整个实现过程记录,只是把知识点摘出来单独解释.可参照代码自己实现.

1.在xml布局文件中添加android.support.v4.view.ViewPager容器及显示导航所用标签android.support.v4.view.PagerTitleStrip,

如我添加的xml内容如下

<android.support.v4.view.ViewPager xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/pager"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity" >
 
    <!--
    This title strip will display the currently visible page title, as well as the pagetitles for adjacent pages.
    -->
 
    <android.support.v4.view.PagerTitleStrip
        android:id="@+id/pager_title_strip"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="top"
        android:background="#33b5e5"
        android:paddingBottom="4dp"
        android:paddingTop="4dp"
        android:textColor="#fff" />
 
</android.support.v4.view.ViewPager>

2.在activity中导入以下包 

import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;

3.声明变量

SectionsPagerAdapter mSectionsPagerAdapter;//此处的SectionsPagerAdapter是继承了FragmentPagerAdapter的类
ViewPager mViewPager;

4.在onCreate中对其进行初始化 

mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
 // Set up the ViewPager with the sections adapter.
mViewPager = (ViewPager) findViewById(R.id.pager);
mViewPager.setAdapter(mSectionsPagerAdapter);

5.添加类SectionsPagerAdapter,我这里使用了3个标签

public class SectionsPagerAdapter extends FragmentPagerAdapter {
 
    public SectionsPagerAdapter(FragmentManager fm) {
      super(fm);
    }
 
    @Override
    public Fragment getItem(int position) {
      // getItem is called to instantiate the fragment for the given page.
      // Return a DummySectionFragment (defined as a static inner class
      // below) with the page number as its lone argument.
      Fragment fragment = new Fragment();
      Bundle args = new Bundle();
      args.putInt("no", position + 1);
      fragment.setArguments(args);
 
      return fragment;
    }
 
    @Override
    public int getCount() {
      // Show 3 total pages.
      return 3;
    }
 
    @Override
    public CharSequence getPageTitle(int position) {
      switch (position) {
      case 0:
        return "标签1";
      case 1:
        return "标签2";
      case 2:
        return "标签3";
      }
      return null;
    }
  }

可以看到在getItem中返回了一个Fragment,这个就是当滑动到不同标签时显示在ViewPager中的内容,Fragment相当于一个Activity,可以在其中的onCreateView函数中构造需要显示的内容并返回
比如,以下代码将显示一个文本信息

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
    Bundle savedInstanceState) {
  TextView textView = new TextView(getActivity());
  textView.setGravity(Gravity.CENTER);
  textView.setText("你选择了标签:"+Integer.toString(getArguments().getInt(
      "no")));
  return textView;
 
}

关于fragment的具体内容,在另一篇转载的文章里更加具体点击打开链接