某些设备上的android应用程序启动错误

Question

06/14 10:51:04: Launching 'app' on Pixel 2 API 27.
$ adb shell am start -n "com.wordsforfun.wordsforplay/com.wordsforfun.words.MainActivity" -a android.intent.action.MAIN -c android.intent.category.LAUNCHER
Error while executing: am start -n "com.wordsforfun.wordsforplay/com.wordsforfun.words.MainActivity" -a android.intent.action.MAIN -c android.intent.category.LAUNCHER
Starting: Intent { act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] cmp=com.wordsforfun.wordsforplay/com.wordsforfun.words.MainActivity }
Error type 3
Error: Activity class {com.wordsforfun.wordsforplay/com.wordsforfun.words.MainActivity} does not exist.

Error while Launching activity

1) 我的 android 应用程序在版本 9 上运行，它在版本 6 中滞后，但在 android 版本 7,8 中崩溃。 2）请任何人都可以帮助我，我是 android studio 的新手 3）现在做很多实验，我已经将我的起始活动更改为其他活动，然后它正在工作我将在这里提供主要活动内容

main activity

package com.wordsforfun.words


import android.content.Intent
import android.media.MediaPlayer
import android.os.Bundle
import android.view.Menu
import android.view.MenuItem
import android.widget.Button
import android.widget.Switch
import androidx.appcompat.app.AppCompatActivity

class MainActivity : AppCompatActivity() {
    lateinit var mp:MediaPlayer
    lateinit var mp2:MediaPlayer
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        var btn = findViewById<Button>(R.id.start)
        var btn2=findViewById<Button>(R.id.btn2)
        val mySwitch=findViewById<Switch>(R.id.switch1)
        mySwitch.setOnCheckedChangeListener { buttonView, isChecked ->
            if(isChecked) {
                mp = MediaPlayer.create(this@MainActivity, resources.getIdentifier(btn.tag as String, "raw", packageName))
                if(mp.isPlaying)
                {
                    return@setOnCheckedChangeListener
                }
                else {
                    mp = MediaPlayer.create(this@MainActivity, resources.getIdentifier(btn.tag as String, "raw", packageName))
                    mp.start()
                }
            }
            else{
                mp.stop()
            }
        }
        btn.setOnClickListener {
            mp2= MediaPlayer.create(this@MainActivity,resources.getIdentifier(btn2.tag as String,"raw",packageName))
            mp2.start()

            var intent = Intent(this@MainActivity,actual_file::class.java)
            startActivity(intent)
        }

    }


    override fun onCreateOptionsMenu(menu: Menu?): Boolean {
        val inflater2=menuInflater
        inflater2.inflate(R.menu.customfile2,menu)
        return true
    }
    override fun onOptionsItemSelected(item: MenuItem): Boolean {
        when (item?.itemId) {
            R.id.instructions -> {
                val intent10= Intent(this@MainActivity,instructions::class.java)
                startActivity(intent10)
                return true
            }
            R.id.moreinfo -> {
                val intent11= Intent(this@MainActivity,more_info::class.java)
                startActivity(intent11)
                return true
            }

        }
        return true
    }

}

this is my xml of main activity




<?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="com.wordsforfun.words.MainActivity">

    <Button
        android:id="@+id/btn2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:tag="click"
        android:text="Button"
        android:visibility="invisible" />

    <ImageView
        android:id="@+id/imageView4"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"
        android:scaleType="centerCrop"
        app:srcCompat="@drawable/p11" />

    <Switch
        android:id="@+id/switch1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_centerHorizontal="true"
        android:text="Music"
        android:textColor="#43034E"
        android:textSize="24sp" />

    <ImageView
        android:layout_width="wrap_content"
        android:layout_height="150dp"
        android:layout_marginTop="30dp"
        android:background="@drawable/p11"
        android:src="@drawable/r" />

    <androidx.cardview.widget.CardView
        android:id="@+id/a"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"
        app:cardCornerRadius="50dp"
        app:cardElevation="50dp"
        app:cardMaxElevation="50dp">

        <Button
            android:id="@+id/start"
            android:layout_width="200sp"
            android:layout_height="60sp"
            android:background="@drawable/y1"
            android:tag="start"
            android:text="Play"
            android:textSize="36sp"
            android:textStyle="italic" />

        <ImageView
            android:id="@+id/imageView6"
            android:layout_width="200sp"
            android:layout_height="60sp"
            app:srcCompat="@drawable/y1" />
    </androidx.cardview.widget.CardView>

</RelativeLayout>

Answer 1

尝试从 manifest.xml 文件中更改活动的名称

如果它看起来像这样：

<activity android:name="MainActivity">

在 Activity 名称的开头添加句点：

<activity android:name=".MainActivity">

或

将包名添加到Activity名称的开头：

<activity android:name="com.wordsforfun.words.MainActivity">

Answer 2

我真的知道了，我在第一次活动中使用了 2 张 0f 800kb 的图像，所以它崩溃了