02-Fragment+布局限定符

1.初级Fragment

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent">

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_gravity="center_horizontal"
    android:text="TextView"/>
</LinearLayout>

<!--右省略-->

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="horizontal" android:layout_width="match_parent"
    android:layout_height="match_parent">

    <!--必须有一个独一无二的id-->
    <fragment
        android:id="@+id/leftFragment"
        android:layout_width="0dp"
        android:layout_height="match_parent"
        android:layout_weight="1"
        android:name="com.my.fragmenttest.LeftFragment"/>

    <fragment
        android:id="@+id/rightFragment"
        android:layout_width="0dp"
        android:layout_height="match_parent"
        android:layout_weight="1"
        android:name="com.my.fragmenttest.RightFragment"/>
</LinearLayout>

class LeftFragment : Fragment() {

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

//右省略

2.动态替换Fragment

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent">

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_gravity="center_horizontal"
    android:text="TextView"/>
</LinearLayout>

<!--右省略-->
<!--Another Fragment省略-->

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="horizontal" android:layout_width="match_parent"
    android:layout_height="match_parent">

    <!--必须有一个独一无二的id-->
    <fragment
        android:id="@+id/leftFragment"
        android:layout_width="0dp"
        android:layout_height="match_parent"
        android:layout_weight="1"
        android:name="com.my.fragmenttest.LeftFragment"/>

    <FrameLayout
        android:id="@+id/rightFragment"
        android:layout_width="0dp"
        android:layout_height="match_parent"
        android:layout_weight="1"/>
</LinearLayout>

class LeftFragment : Fragment() {

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

//右省略
//Another Fragment省略

class MainActivity : AppCompatActivity() {

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

        leftFragmentButton.setOnClickListener {
            replaceFragment(AnotherFragment())
        }
        replaceFragment(RightFragment())
    }

    /**
     * 替换Fragment
     */
    private fun replaceFragment(fragment : Fragment){
        val fragmentManager = supportFragmentManager
        val transaction = fragmentManager.beginTransaction()
        transaction.replace(R.id.rightFragment,fragment)
        transaction.commit()
    }
}

3.Fragment返回栈

private fun replaceFragment(fragment : Fragment){
    val fragmentManager = supportFragmentManager
    val transaction = fragmentManager.beginTransaction()
    transaction.replace(R.id.rightFragment,fragment)
    //将Fragment加入返回栈，不然通过按钮添加Fragment后，点击返回按钮，程序直接退出
    transaction.addToBackStack(null)
    transaction.commit()
}

4.Fragment和Activity的交互

//在Activity中获取Fragment
val rightFragment =
supportFragmentManager.findFragmentById(R.id.rightFragment) as RightFragment
//findFragmentById和findViewById相同，可以省略
val f = rightFragment as RightFragment

//Fragment中获取Activity
if (activity != null){
    val mainActivity = activity as MainActivity
}

5.Fragment声明周期

class AnotherFragment : Fragment() {

    companion object {
        const val TAG = "AnotherFragment"
    }

    /**
     * Fragment和Activity建立关系是调用
     */
    override fun onAttach(context: Context) {
        super.onAttach(context)
        Log.e(TAG,"onAttach")
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        Log.e(TAG,"onCreate")
    }

    /**
     * 为Fragment创建视图时调用
     */
    override fun onCreateView(
        inflater: LayoutInflater,
        container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        Log.e(TAG,"onCreateView")
        return inflater.inflate(R.layout.another_right_framgent,container,false)
    }

    /**
     * Activity被创建时调用
     */
    override fun onActivityCreated(savedInstanceState: Bundle?) {
        super.onActivityCreated(savedInstanceState)
        Log.e(TAG,"onActivityCreated")
    }

    override fun onStart() {
        super.onStart()
        Log.e(TAG,"onStart")
    }

    override fun onResume() {
        super.onResume()
        Log.e(TAG,"onResume")
    }

    override fun onPause() {
        super.onPause()
        Log.e(TAG,"onPause")
    }

    override fun onStop() {
        super.onStop()
        Log.e(TAG,"onStop")
    }

    /**
     * 当与Fragment相关联的Activity被移除时调用
     */
    override fun onDestroyView() {
        super.onDestroyView()
        Log.e(TAG,"onDestroyView")
    }

    override fun onDestroy() {
        super.onDestroy()
        Log.e(TAG,"onDestroy")
    }

    /**
     * 当Fragment和Activity接触关联时调用
     */
    override fun onDetach() {
        super.onDetach()
        Log.e(TAG,"onDetach")
    }
}

6.布局限定符

1:layout_large。
2:layout_sw600dp。

本文地址：https://blog.csdn.net/qq_44637792/article/details/107900738