控件-----fragment使用（一）

Fragment的使用一般可以分为两种场景：一、Fragment与ViewPager连用，二、Fragment单独使用。

一、Fragment与ViewPager连用

1、在activity的xml里添加ViewPager控件

<android.support.v4.view.ViewPager
    android:id="@+id/vp_fragment"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:visibility="gone"
    android:text="Hello World!" />

2、新建继承自Fragment（v4包）的类，可起名为Fragment1（可在包上右键new -- fragment -- blank fragment），类似的可新建多个（与viewPager连用）

class Fragment1 : Fragment() {
    private var param1: String? = null
    private var param2: String? = null
    private var listener: OnFragmentInteractionListener? = null

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        arguments?.let {
            param1 = it.getString(ARG_PARAM1)
            param2 = it.getString(ARG_PARAM2)
        }
    }

    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
        return inflater.inflate(R.layout.fragment_fragment1, container, false)
    }

    fun onButtonPressed(uri: Uri) {
        listener?.onFragmentInteraction(uri)
    }

    override fun onAttach(context: Context) {
        super.onAttach(context)
        if (context is OnFragmentInteractionListener) {
            listener = context
        } else {
            throw RuntimeException(context.toString() + " must implement OnFragmentInteractionListener")
        }
    }

    override fun onDetach() {
        super.onDetach()
        listener = null
    }

    //需要注意的是这个接口，activity必须实现，这个可以实现fragment向activity发消息
    interface OnFragmentInteractionListener {
        fun onFragmentInteraction(uri: Uri)//参数可以是其他类型
    }

    companion object {
        private const val ARG_PARAM1 = "param1"
        private const val ARG_PARAM2 = "param2"
        @JvmStatic
        fun newInstance(param1: String, param2: String) =
                Fragment1().apply {
                    arguments = Bundle().apply {
                        putString(ARG_PARAM1, param1)
                        putString(ARG_PARAM2, param2)
                    }
                }
    }
}

3、新建继承自FragmentAdapter的类，可，命名为MyFragmentAdapter

class MyFragmentAdapter(fm: FragmentManager, fragments: MutableList<Fragment>) : FragmentPagerAdapter(fm) {

    private var fragmentList: MutableList<Fragment> = fragments

    override fun getItem(position: Int): Fragment {
        return fragmentList[position]
    }

    override fun getCount(): Int {
        return fragmentList.size
    }

}

4、准备工作准备好以后，开始添加Activity里的代码。注意要继承FragmentActivity类。

class MyFragmentActivity : FragmentActivity()
        , Fragment1.OnFragmentInteractionListener
        , Fragment2.OnFragmentInteractionListener {

    override fun onFragmentInteraction222(string: String) {
        Log.d("baibai", "onFragmentInteraction222")
        Log.d("baibai", string)
    }

    override fun onFragmentInteraction(uri: Uri) {

    }

    private lateinit var mFragments: MutableList<Fragment>
    private lateinit var mFragment1: Fragment1
    private lateinit var mFragment2: Fragment2
    private lateinit var mFragmentAdapter: MyFragmentAdapter

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_my_fragment)

        initFragment()
        initListener()

    }

    private fun initFragment() {
        mFragment1 = Fragment1.newInstance("bai", "yun")
        mFragment2 = Fragment2.newInstance("111", "222")
        mFragments = mutableListOf()
        mFragments.add(mFragment1)
        mFragments.add(mFragment2)
    }

    private fun initListener() {
        mFragmentAdapter = MyFragmentAdapter(this.supportFragmentManager, mFragments)
        vp_fragment.adapter = mFragmentAdapter
        vp_fragment.setOnPageChangeListener(object : ViewPager.OnPageChangeListener {
            override fun onPageScrollStateChanged(state: Int) {

            }

            override fun onPageScrolled(position: Int, positionOffset: Float, positionOffsetPixels: Int) {
             //滑动的过程中
            }

            override fun onPageSelected(position: Int) {
            //viewPager确定某一页选中后
            }

        })
    }

}