问题描述
我正在制作Kotlin食谱应用程序,我有一个菜名列表,并带有一个按钮,以查看每当在列表视图中添加新菜时都会生成的菜。该按钮应该将用户导航到一个新的活动,其中将显示菜谱。但是,该按钮不起作用。我已经尝试了一些建议的解决方案,但仍然行不通。
列表的xml文件:
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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"
android:background="@android:color/darker_gray"
tools:context=".ViewRecipe">
<ListView
android:id="@+id/recipeList"
android:layout_width="367dp"
android:layout_height="565dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="@+id/textView2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="39dp"
android:text="Recipe List"
android:textSize="18sp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
按钮的XML:
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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=".Recipes">
<TextView
android:id="@+id/recipeView2"
android:layout_width="228dp"
android:layout_height="28dp"
android:layout_marginStart="23dp"
android:layout_marginTop="47dp"
android:text="TextView"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<Button
android:id="@+id/recipeDetails"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="33dp"
android:layout_marginEnd="20dp"
android:text="View"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
列表视图的Kotlin文件:
package com.example.recipeapp
import android.content.Intent
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.widget.Button
import android.widget.ListView
import com.google.firebase.database.*
class ViewRecipe : AppCompatActivity() {
lateinit var ref: DatabaseReference
lateinit var recipeList: MutableList<AddRecipeModelClass>
lateinit var listView: ListView
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_view_recipe)
recipeList = mutablelistof()
ref = FirebaseDatabase.getInstance().getReference("addRecipes")
listView = findViewById(R.id.recipeList)
ref.addValueEventListener(object: ValueEventListener {
override fun onCancelled(error: DatabaseError) {
Todo("Not yet implemented")
}
override fun onDataChange(snapshot: DataSnapshot) {
if (snapshot.exists()) {
recipeList.clear()
for(h in snapshot.children){
val recipe = h.getValue(AddRecipeModelClass::class.java)
recipeList.add(recipe!!)
}
val adapter = RecipeAdapter(applicationContext,R.layout.activity_recipes,recipeList)
listView.adapter = adapter
}
}
});
}
}
按钮的Kotlin文件:
package com.example.recipeapp
import android.content.Intent
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.widget.Button
class Recipes : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_recipes)
val navView = findViewById<Button>(R.id.recipeDetails)
navView.setonClickListener{
val intent = Intent(this,RecipeDetails::class.java)
startActivity(intent)
}
}
}
RecipeAdapter.kt
package com.example.recipeapp
import android.content.Context
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.ArrayAdapter
import android.widget.TextView
class RecipeAdapter(val mCtx: Context,val layoutResId: Int,val recipeList: List<AddRecipeModelClass>)
: ArrayAdapter<AddRecipeModelClass>(mCtx,layoutResId,recipeList) {
override fun getView(position: Int,convertView: View?,parent: ViewGroup): View {
val layoutInflater: LayoutInflater = LayoutInflater.from(mCtx)
val view: View = layoutInflater.inflate(layoutResId,null)
val recipeView = view.findViewById<TextView>(R.id.recipeView2)
val recipe = recipeList[position]
recipeView.text = recipe.dishName
return view
}
}
编辑:
我发现此问题正在发生,因为“视图”按钮位于列表视图中。我尝试使用放置在列表视图外部的“按钮”,但效果很好。我无法使用互联网上找到的解决方案来解决它。
图像显示2种类型的按钮。视图在列表视图内部,按钮在列表视图外部。
任何帮助将不胜感激。
解决方法
我没有阅读完整的代码,但是我发现的一个问题是:
navView.setOnClickListener{
val intent = Intent(this,RecipeDetails::class.java)
// ^^^^
startActivity(intent)
}
该范围中的this
是指传递给View.OnClickListener
函数的setOnclickListener
对象。不在应用程序上下文中。
来自kotlin docs:
要从外部范围(类,扩展功能或 带有接收方的标记函数文字),我们将this @ label写入其中 @label是作用域上的标签,
因此,您应该改为这样做:
navView.setOnClickListener{
val intent = Intent(this@Recipes,RecipeDetails::class.java)
// ^^^^ note the label @Recipes
startActivity(intent)
}
或者,您可以在Intent
函数的View.OnClickListener
对象外部调用onCreate
构造函数:
val intent = Intent(this,RecipeDetails::class.java)
val navView = findViewById<Button>(R.id.recipeDetails)
navView.setOnClickListener{
startActivity(intent)
}
,
将其放入您的活动类中,并确保AddRecipeModelClass可包裹
private val onItemAction: (AddRecipeModelClass) -> Unit = { it ->
val intent = Intent(this@ViewRecipe,RecipeDetails::class.java)
intent.putExtra("recipe",it)
startActivity(intent)
}
通过意图进行新活动获取食谱
将点击监听器添加到适配器的getView
class RecipeAdapter(val mCtx: Context,val layoutResId: Int,val recipeList: List<AddRecipeModelClass>,private val onItemSelected: (AddRecipeModelClass) -> Unit?)
: ArrayAdapter<AddRecipeModelClass>(mCtx,layoutResId,recipeList) {
override fun getView(position: Int,convertView: View?,parent: ViewGroup): View {
val layoutInflater: LayoutInflater = LayoutInflater.from(mCtx)
val view: View = layoutInflater.inflate(layoutResId,null)
val recipeView = view.findViewById<TextView>(R.id.recipeView2)
val btn= findViewById<Button>(R.id.recipeDetails)
val recipe = recipeList[position]
btn.setOnClickListener{
onItemSelected(recipe)
}
recipeView.text = recipe.dishName
return view
}
}
向构造函数添加函数
val adapter = RecipeAdapter(applicationContext,R.layout.activity_recipes,recipeList,onItemAction)