MainActivity中的Intent启动另一个活动，阻止MainActivity代码执行

Question

我是kotlin的新手，我正在尝试制作一个带有基于NumberPicker的时间选择器的导航栏，以及另外两个空片段(目前至少(，但我的问题是，如果我启动了一个意图，导航栏就不会显示，当我没有将其放入代码(intent(时，导航栏会正常工作，我做错了什么，我是不是错过了什么？？

主要活动.kt

package com.example.helloworld
import android.content.Intent
import android.os.Bundle
import androidx.appcompat.app.AppCompatActivity
import androidx.fragment.app.Fragment
import com.example.helloworld.databinding.ActivityMainBinding


class MainActivity : AppCompatActivity() {

private lateinit var binding: ActivityMainBinding
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
binding = ActivityMainBinding.inflate(layoutInflater)
setContentView(binding.root)

binding.bottomNavigationView.setOnItemSelectedListener {
when (it.itemId) {
R.id.first -> replaceFragment(Home())
R.id.second -> replaceFragment(Voices())
R.id.third -> replaceFragment(Settings())
else -> {
}
}
true
}

replaceFragment(Home())
Intent(this, SecondActivity::class.java).also {
startActivity(it)

}
}
private fun replaceFragment(fragment: Fragment) {
val fragmentManager = supportFragmentManager
val fragmentTransaction = fragmentManager.beginTransaction()
fragmentTransaction.replace(R.id.frameLayout, fragment)
fragmentTransaction.commit()
}
}

第二活动.kt

package com.example.helloworld
import android.os.Bundle
import androidx.appcompat.app.AppCompatActivity
import kotlinx.android.synthetic.main.activity_second.*
class SecondActivity : AppCompatActivity()  {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_second)

numPickerMin2.minValue = 0
numPickerMin2.maxValue = 23
numPickerSec2.minValue = 0
numPickerSec2.maxValue = 59
var min = 0
var sec = 0
var amOrPm = ""

val str = arrayOf<String>("AM", "PM")
numPickerAM2.minValue = 0
numPickerAM2.maxValue = (str.size - 1)
numPickerAM2.displayedValues = str
numPickerMin2.setOnValueChangedListener { numberPicker, i, i2 ->
min = numberPicker.value
}
numPickerSec2.setOnValueChangedListener { numberPicker, i, i2 ->
sec = numberPicker.value
}
numPickerAM2.setOnValueChangedListener { numberPicker, i, i2 ->
val i = numberPicker.value
amOrPm = str[i]
}

btGetValue2.setOnClickListener {
reminderTime2.text = "$min : $sec : $amOrPm"
}
}
}

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
package="com.example.helloworld"
android:installLocation="preferExternal"
android:versionCode="1"
android:versionName="0.2">
<uses-sdk
android:minSdkVersion="18"
android:targetSdkVersion="27" />
<application
android:allowBackup="true"
android:dataExtractionRules="@xml/data_extraction_rules"
android:fullBackupContent="@xml/backup_rules"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:roundIcon="@mipmap/ic_launcher_round"
android:supportsRtl="true"
tools:targetApi="31"
android:theme="@style/Theme.HelloWorld">
<activity
android:name=".MainActivity"
android:exported="true"
android:screenOrientation="sensorPortrait"
android:label="@string/app_name"
android:launchMode="singleInstance">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name=".SecondActivity">
</activity>
</application>
</manifest>

ActivityMain.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=".MainActivity">

<FrameLayout
android:id="@+id/frameLayout"
android:layout_width="0dp"
android:layout_height="0dp"
app:layout_constraintBottom_toTopOf="@id/bottomNavigationView"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent">
</FrameLayout>
<com.google.android.material.bottomnavigation.BottomNavigationView
android:id="@+id/bottomNavigationView"
android:layout_width="0dp"
android:layout_height="wrap_content"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:menu="@menu/bottom_nav"/>

</androidx.constraintlayout.widget.ConstraintLayout>

activity_second.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"
android:layout_marginStart="1dp"
android:layout_marginTop="1dp"
android:layout_marginEnd="1dp"
android:layout_marginBottom="1dp"
android:background="@color/BackgroundFirst"
tools:context=".Home">

<com.google.android.material.textfield.TextInputLayout
android:id="@+id/textInputLayout4"
style="@style/Widget.MaterialComponents.TextInputLayout.OutlinedBox.Dense.ExposedDropdownMenu"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="16dp"
android:layout_marginTop="55dp"
app:layout_constraintEnd_toStartOf="@+id/guideline2"
app:layout_constraintStart_toStartOf="@+id/guideline2"
app:layout_constraintTop_toTopOf="@+id/guideline3">
<AutoCompleteTextView
android:id="@+id/dropdown_field"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:inputType="none"
android:text="Choose Alert"/>
</com.google.android.material.textfield.TextInputLayout>

<com.shawnlin.numberpicker.NumberPicker
android:id="@+id/numPickerMin2"
android:layout_width="wrap_content"
android:layout_height="0dp"
android:layout_centerInParent="true"
android:layout_marginEnd="23dp"
android:gravity="center"
android:theme="@style/AppTheme.Picker"
app:layout_constraintBottom_toBottomOf="@+id/numPickerSec2"
app:layout_constraintEnd_toStartOf="@+id/numPickerSec2"
app:layout_constraintTop_toTopOf="@+id/numPickerSec2"
app:np_dividerColor="@color/black"
app:np_dividerDistance="55dp"
app:np_dividerLength="100dp"
app:np_dividerThickness="3dp"
app:np_formatter=""
app:np_height="180dp"
app:np_max="12"
app:np_min="0"
app:np_selectedTextColor="@color/selected"
app:np_selectedTextSize="60sp"
app:np_textAlign="textAlignCenter"
app:np_textColor="@color/black"
app:np_textSize="40sp"
app:np_typeface="@string/roboto_light"
app:np_value="1"
app:np_wheelItemCount="10"
app:np_width="74dp"
app:np_wrapSelectorWheel="true" />
<com.shawnlin.numberpicker.NumberPicker
android:id="@+id/numPickerSec2"

android:layout_width="wrap_content"
android:layout_height="0dp"
android:layout_centerInParent="true"
android:layout_marginTop="37dp"
android:layout_marginEnd="9dp"
android:layout_marginBottom="27dp"
android:gravity="center"
android:theme="@style/AppTheme.Picker"
app:layout_constraintBottom_toTopOf="@+id/textInputLayout4"
app:layout_constraintEnd_toStartOf="@+id/numPickerAM2"
app:layout_constraintTop_toBottomOf="@+id/imageView2"
app:np_dividerColor="@color/black"
app:np_dividerDistance="55dp"
app:np_dividerLength="100dp"
app:np_dividerThickness="3dp"
app:np_formatter=""
app:np_height="180dp"
app:np_max="59"
app:np_min="0"
app:np_selectedTextColor="@color/selected"
app:np_selectedTextSize="60sp"
app:np_textAlign="textAlignCenter"
app:np_textColor="@color/black"
app:np_textSize="40sp"
app:np_typeface="@string/roboto_light"
app:np_value="1"
app:np_wheelItemCount="10"
app:np_width="74dp"
app:np_wrapSelectorWheel="true" />
<com.shawnlin.numberpicker.NumberPicker
android:id="@+id/numPickerAM2"
android:layout_width="wrap_content"
android:layout_height="0dp"
android:layout_centerInParent="true"
android:layout_marginStart="56dp"
android:layout_marginEnd="55dp"
android:gravity="center"
android:theme="@style/AppTheme.Picker"
app:layout_constraintBottom_toBottomOf="@+id/numPickerSec2"
app:layout_constraintEnd_toEndOf="@+id/imageView2"
app:layout_constraintStart_toStartOf="@+id/guideline2"
app:layout_constraintTop_toTopOf="@+id/numPickerSec2"
app:np_dividerColor="@color/black"
app:np_dividerDistance="55dp"
app:np_dividerLength="100dp"
app:np_dividerThickness="3dp"
app:np_formatter=""
app:np_height="180dp"
app:np_max="1"
app:np_min="0"
app:np_selectedTextColor="@color/selected"
app:np_selectedTextSize="60sp"
app:np_textAlign="textAlignCenter"
app:np_textColor="@color/black"
app:np_textSize="40sp"
app:np_typeface="@string/roboto_light"
app:np_value="1"
app:np_wheelItemCount="10"
app:np_width="74dp"
app:np_wrapSelectorWheel="true" />
<Button
android:id="@+id/btGetValue2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:layout_marginBottom="78dp"
android:backgroundTint="@color/selected"
android:baselineAligned="false"
android:text="Get Time"
android:textSize="15sp"
app:layout_constraintBottom_toTopOf="@+id/reminderTime2"
app:layout_constraintEnd_toStartOf="@+id/guideline2"
app:layout_constraintStart_toStartOf="@+id/guideline2" />
<TextView
android:id="@+id/reminderTime2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal"
android:layout_marginBottom="63dp"
android:text="Time"
android:textSize="40sp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toStartOf="@+id/guideline2"
app:layout_constraintStart_toStartOf="@+id/guideline2" />
<ImageView
android:id="@+id/imageView2"
android:layout_width="351dp"
android:layout_height="103dp"
android:layout_marginTop="16dp"
android:layout_weight="1"
android:scaleX="1.5"
android:scaleY="1.5"
app:layout_constraintEnd_toStartOf="@+id/guideline2"
app:layout_constraintStart_toStartOf="@+id/guideline2"
app:layout_constraintTop_toTopOf="parent"
app:srcCompat="@drawable/helloday_logo" />
<androidx.constraintlayout.widget.Guideline
android:id="@+id/guideline2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical"
app:layout_constraintGuide_percent="0.5"
/>
<androidx.constraintlayout.widget.Guideline
android:id="@+id/guideline3"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="horizontal"
app:layout_constraintGuide_percent="0.5" />

</androidx.constraintlayout.widget.ConstraintLayout>

Answer 1

与其创建第二个活动，我建议您创建另一个片段。以与您当前应用程序中的其他片段相同的方式使用它。