Fragment简单使用

Fragment可以理解为小型的Activity，可以嵌入其中使用
首先创建Fragment布局

<?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">

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:text="Button" />
</LinearLayout>

这里只是简单的放置了一个button
然后在main.xml中引入fragment

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <fragment
        android:layout_width="match_parent"
        android:layout_height="match_parent"
         android:name="com.example.fragmenttest.LeftFragment"
        android:id="@+id/leftFrag"/>


</LinearLayout>

还有有一个对应的类

package com.example.fragmenttest

import android.os.Bundle
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.fragment.app.Fragment

class LeftFragment : Fragment() {

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

简单的就是重写其中的onCreateView()方法加载布局

替换AnotherFragment以及实现返回栈

package com.example.fragmenttest

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.widget.Button
import android.widget.FrameLayout
import androidx.fragment.app.Fragment

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

        val button : Button = findViewById(R.id.button)

        button.setOnClickListener {
            replaceFragment(AnotherRightFrag())
        }
        //replaceFragment(RightFragment())
    }

    private fun replaceFragment(fragment: Fragment){
        val fragmentManager = supportFragmentManager
        val transaction = fragmentManager.beginTransaction()
        //transaction.replace(R.id.rightLayout,fragment)
        transaction.addToBackStack(null)//在Fragment中实现返回栈
        transaction.commit()
    }
}