android-fragments - Activity 独立加载，但不在 Fragment 中

Question

我是移动开发的新手。我已经使用 Kotlin 启动了我的移动应用程序。我有一个 Activity (ProductsActivity.kt)，它加载 RecyclerView，ImageView 和 TextView 从 MySQL 获取数据，这是独立工作的。现在，我希望这个 Activity 加载到 Fragment 中，我尝试使用 Inflater 加载，但它没有显示任何数据。以下是我的代码，请帮助我如何实现相同的目标。提前致谢。

MainActivity.kt

package com.example.administrator.zmaart

import android.content.Intent
import android.os.Bundle
import android.support.design.widget.NavigationView
import android.support.v4.app.Fragment
import android.support.v4.view.GravityCompat
import android.support.v4.widget.DrawerLayout
import android.support.v7.app.ActionBarDrawerToggle
import android.support.v7.app.AppCompatActivity
import android.support.v7.widget.Toolbar
import android.view.Menu
import android.view.MenuItem
import android.view.View
import android.widget.Toast

class MainActivity : AppCompatActivity(),         
NavigationView.OnNavigationItemSelectedListener {

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_main)
    val toolbar = findViewById<View>(R.id.toolbar) as Toolbar
    setSupportActionBar(toolbar)

    val drawer = findViewById<View>(R.id.drawer_layout) as DrawerLayout
    val toggle = ActionBarDrawerToggle(
            this, drawer, toolbar, R.string.navigation_drawer_open, 
R.string.navigation_drawer_close)
    drawer.addDrawerListener(toggle)
    toggle.syncState()

    val navigationView = findViewById<View>(R.id.nav_view) as 
NavigationView
    navigationView.setNavigationItemSelectedListener(this)

    displaySelectedScreen(R.id.nav_home)
}

private var backButtonCount: Int = 0

override fun onBackPressed() {
    val drawer = findViewById<View>(R.id.drawer_layout) as DrawerLayout
    if (drawer.isDrawerOpen(GravityCompat.START)) {
        drawer.closeDrawer(GravityCompat.START)
    } else {
        if (backButtonCount >= 1) {
            val intent = Intent(Intent.ACTION_MAIN)
            intent.addCategory(Intent.CATEGORY_HOME)
            intent.flags = Intent.FLAG_ACTIVITY_NEW_TASK
            startActivity(intent)
        } else {
            Toast.makeText(this, "Press the back button once again to close the application.", Toast.LENGTH_SHORT).show()
            backButtonCount++
        }
    }
}

override fun onCreateOptionsMenu(menu: Menu): Boolean {
    // Inflate the menu; this adds items to the action bar if it is present.
    menuInflater.inflate(R.menu.main, menu)
    return true
}

override fun onOptionsItemSelected(item: MenuItem): Boolean {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    val id = item.itemId


    return if (id == R.id.action_settings) {
        true
    } else super.onOptionsItemSelected(item)

}

override fun onNavigationItemSelected(item: MenuItem): Boolean {

    displaySelectedScreen(item.itemId)

    return true
}

private fun displaySelectedScreen(itemId: Int) {

    //creating fragment object
    var fragment: Fragment? = null

    //initializing the fragment object which is selected
    when (itemId) {
        R.id.nav_home -> fragment = home()
        R.id.nav_orders -> fragment = orders()
        R.id.nav_wishlist -> {
            val intent = Intent(this@MainActivity, 
ProductsActivity::class.java)
            [e-mail](intent)
        }
        R.id.nav_logout -> {
            val sharedPreferences = getSharedPreferences("SharedPref", 0)
            val editor = sharedPreferences.edit()
            editor.clear()
            editor.apply()
            val intent = Intent(this@MainActivity, Login_Page::class.java)
            [e-mail](intent)
        }
    }

    //replacing the fragment
    if (fragment != null) {
        val ft = supportFragmentManager.beginTransaction()
        ft.replace(R.id.content_frame, fragment)
        ft.commit()
    }

    val drawer = findViewById<View>(R.id.drawer_layout) as DrawerLayout
    drawer.closeDrawer(GravityCompat.START)
}
}

活动产品.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    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=".ProductsActivity">

    <android.support.v7.widget.RecyclerView
    android:id="@+id/recylcerView1"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:layout_editor_absoluteX="745dp"
    tools:layout_editor_absoluteY="-51dp" />

</RelativeLayout>

ProductsActivity.kt

package com.example.administrator.zmaart

import android.os.Bundle
import android.support.v7.app.AppCompatActivity
import android.support.v7.widget.LinearLayoutManager
import android.support.v7.widget.RecyclerView
import com.android.volley.Request
import com.android.volley.Response
import com.android.volley.toolbox.StringRequest
import com.android.volley.toolbox.Volley
import org.json.JSONArray
import org.json.JSONException
import java.util.*

class ProductsActivity : AppCompatActivity() {

private lateinit var productList: MutableList<Product>

private lateinit var recyclerView: RecyclerView


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

    recyclerView = findViewById(R.id.recylcerView1)
    recyclerView.setHasFixedSize(false)
    recyclerView.layoutManager = LinearLayoutManager(this)

    productList = ArrayList()

    loadProducts()
}

private fun loadProducts() {

    /*
     * Creating a String Request
     * The request type is GET defined by first parameter
     * The URL is defined in the second parameter
     * Then we have a Response Listener and a Error Listener
     * In response listener we will get the JSON response as a String
     * */
    val stringRequest = StringRequest(Request.Method.GET, URL_PRODUCTS,
            Response.Listener { response ->
                try {
                    //converting the string to json array object
                    val array = JSONArray(response)

                    //traversing through all the object
                    for (i in 0 until array.length()) {

                        //getting product object from json array
                        val product = array.getJSONObject(i)

                        //adding the product to product list
                        productList.add(Product(
                                product.getString("prod_id_sha"),
                                product.getString("prod_title"),
                                product.getDouble("prod_price"),
                                product.getDouble("prod_price2"),
                                product.getString("img_thumbnail")
                        ))
                    }

                    //creating adapter object and setting it to recyclerview
                    val adapter = ProductsAdapter(this@ProductsActivity, productList)
                    recyclerView.adapter = adapter
                } catch (e: JSONException) {
                    e.printStackTrace()
                }
            },
            Response.ErrorListener { })

    //adding our stringrequest to queue
    Volley.newRequestQueue(this).add(stringRequest)
}

companion object {

    //this is the JSON Data URL
    //make sure you are using the correct ip else it will not work
    private const val URL_PRODUCTS = "localhost/app/load_prod.php"
}
}

home.kt（我想加载activity_products.xml）

package com.example.administrator.zmaart

import android.os.Bundle
import android.support.v4.app.Fragment
import android.support.v7.widget.RecyclerView
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup

class home : Fragment() {

private lateinit var productList: MutableList<Product>

private lateinit var recyclerView: RecyclerView


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

override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
    super.onViewCreated(view, savedInstanceState)
    activity!!.title = "Home"
}
}

请让我知道是否包含任何其他代码来帮助您帮助我。

标签： android-fragmentsandroid-activitykotlin