【发布时间】：2020-03-05 23:33:35
【问题描述】：
我想做的事
我想获取用户在依赖微调器上选择的数据。
在我当前的代码中，成功从第一个微调器获取数据，但我无法从第二个微调器获取数据。
问题
我应该如何修复我的代码以获取用户选择的适当数据？
- 在这种情况下，第二个 textView 应该是 BMW，但它是 Audi，它是第二个 spinner 的第一个候选者。
- 第一个 textView 在用户选择后发生更改。在这种情况下，它从 motor 变为 mobile，但同样，第二个 textView 仍然是第二个 spinner 的第一个候选者。
当前代码
MainActivity.kt
package com.example.spinner
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.view.Menu
import android.view.MenuItem
import android.app.Activity
import android.content.Intent
import android.util.Log
import android.view.View
import android.widget.AdapterView
import android.widget.Spinner
import android.widget.ArrayAdapter
import kotlinx.android.synthetic.main.activity_main.*
import android.widget.AdapterView.OnItemSelectedListener
import android.widget.Toast
class MainActivity : AppCompatActivity(), AdapterView.OnItemSelectedListener {
var spinner1: Spinner? = null
var spinner2: Spinner? = null
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
spinner1 = findViewById(R.id.spinner1) as Spinner
spinner2 = findViewById(R.id.spinner2) as Spinner
val adapter1 = ArrayAdapter.createFromResource(
this,
R.array.array1, android.R.layout.simple_spinner_item
)
spinner1?.setAdapter(adapter1)
spinner1?.setOnItemSelectedListener(this)
}
override fun onCreateOptionsMenu(menu: Menu): Boolean {
// Inflate the main; 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.getItemId()
return if (id == R.id.action_settings) {
true
} else super.onOptionsItemSelected(item)
}
override fun onItemSelected(
parent: AdapterView<*>, view: View, position: Int,
id: Long
) {
if (spinner1?.getSelectedItem() == "mobile") {
Toast.makeText(
applicationContext, "Mobil dipilih",
Toast.LENGTH_SHORT
).show()
val adapter2 = ArrayAdapter.createFromResource(
this,
R.array.mobile_array, android.R.layout.simple_spinner_item
)
spinner2?.setAdapter(adapter2)
spinner2?.setOnItemSelectedListener(this)
} else {
val adapter2 = ArrayAdapter.createFromResource(
this,
R.array.motor_array, android.R.layout.simple_spinner_item
)
spinner2?.setAdapter(adapter2)
spinner2?.setOnItemSelectedListener(this)
}
// here I try to put the selected contents to variables
val spinner1_content = spinner1?.getSelectedItem() as String
textView1.text = spinner1_content
val spinner2_content = spinner2?.getSelectedItem() as String
textView2.text = spinner2_content
}
override fun onNothingSelected(parent: AdapterView<*>?) {
}
}
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="com.example.stackspinner.MainActivity" >
<Spinner
android:id="@+id/spinner1"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
<Spinner
android:id="@+id/spinner2"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="@+id/spinner1" />
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="center_horizontal"
android:orientation="vertical">
<TextView
android:id="@+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textColor="#00f"
android:layout_marginTop="100dp"
android:textSize="40sp" />
<TextView
android:id="@+id/textView2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textColor="#00f"
android:layout_marginTop="100dp"
android:textSize="40sp" />
</LinearLayout>
</RelativeLayout>
字符串.xml
<resources>
<string name="app_name">Application Name</string>
<string name="hello_world">Hello world!</string>
<string name="action_settings">Settings</string>
<string-array name="array1">
<item>mobile</item>
<item>motor</item>
</string-array>
<string-array name="mobile_array">
<item>Android</item>
<item>blackberry</item>
<item>apple</item>
</string-array>
<string-array name="motor_array">
<item>Audi</item>
<item>BMW</item>
<item>unicorn</item>
</string-array>
</resources>
听到答案后的当前代码
MainActivity.kt
package com.example.spinner
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.view.Menu
import android.view.MenuItem
import android.app.Activity
import android.content.Intent
import android.util.Log
import android.view.View
import android.widget.AdapterView
import android.widget.Spinner
import android.widget.ArrayAdapter
import kotlinx.android.synthetic.main.activity_main.*
import android.widget.AdapterView.OnItemSelectedListener
import android.widget.Toast
class MainActivity : AppCompatActivity(), AdapterView.OnItemSelectedListener {
var spinner1: Spinner? = null
var spinner2: Spinner? = null
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
spinner1 = findViewById(R.id.spinner1) as Spinner
spinner2 = findViewById(R.id.spinner2) as Spinner
val adapter1 = ArrayAdapter.createFromResource(
this,
R.array.array1, android.R.layout.simple_spinner_item
)
spinner1?.setAdapter(adapter1)
spinner1?.setOnItemSelectedListener(this)
val adapter2 = ArrayAdapter.createFromResource(
this,
R.array.array1, android.R.layout.simple_spinner_item
)
spinner2?.setAdapter(adapter2)
spinner2?.setOnItemSelectedListener(this)
}
override fun onCreateOptionsMenu(menu: Menu): Boolean {
// Inflate the main; 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.getItemId()
return if (id == R.id.action_settings) {
true
} else super.onOptionsItemSelected(item)
}
override fun onItemSelected(
parent: AdapterView<*>, view: View, position: Int,
id: Long
) {
if (spinner1?.getSelectedItem() == "mobile") {
Toast.makeText(
applicationContext, "Mobil dipilih",
Toast.LENGTH_SHORT
).show()
val adapter2 = ArrayAdapter.createFromResource(
this,
R.array.mobile_array, android.R.layout.simple_spinner_item
)
spinner2?.setAdapter(adapter2)
} else {
val adapter2 = ArrayAdapter.createFromResource(
this,
R.array.motor_array, android.R.layout.simple_spinner_item
)
spinner2?.setAdapter(adapter2)
}
// here I try to put the selected contents to variables
val spinner1_content = spinner1?.getSelectedItem() as String
textView1.text = spinner1_content
val spinner2_content = spinner2?.getSelectedItem() as String
textView2.text = spinner2_content
}
override fun onNothingSelected(parent: AdapterView<*>?) {
}
}
【问题讨论】：
-
您从未在
onCreate方法中向spinner2添加适配器或侦听器。 -
感谢您的评论。你能用代码解释一下它的细节吗？我可以看到 spinner2 的变化取决于选定的 spinner1，用户可以选择 spinner2 上的每个元素。
-
您在代码中的任何地方都没有调用
spinner2?.setOnItemSelectedListener，因此当您在spinner2中选择项目时不会发生任何事情。 -
我已将 MainActivity.kt 更改为
spinner2?.setOnItemSelectedListener但在这种情况下，当我更改第一个微调器时，应用程序在模拟器上关闭，第二个微调器的 textView 也没有改变. -
堆栈跟踪会告诉你它为什么会崩溃。至于您的逻辑，由于两个微调器都使用相同的侦听器，因此您需要通过使用
parent的值来区分哪一个刚刚被更改。喜欢when(parent) { spinner1 -> { /* logic for spinner 1 */ } spinner2 -> { /* logic for spinner2 */ } }
标签： java android xml kotlin spinner