Android studio的MainActivity类文件报错不知道怎么弄得，哪位大佬帮帮忙？

Posted 2023-04-05

参考技术A MainActivity继承的父类AppCompatActivity是有版本android限制的，低于多少版本不支持，具体你去查一下，这边没有找到支持的依赖包。看报错信息也是没有版本支持，可能你的项目配置信息没弄好，重新梳理一下，把sdk的版本和支持依赖包版本统一适配起来。 参考技术B 你的SDK版本设置有问题，找不到API v28，建议升级一下你的sdk；
还有你这图太模糊，建议看一下build.gradle文件，里面引用的libraries版本应该不兼容 参考技术C 下面贴上代码：
package com.example.urien.secondapp;
import android.content.Intent;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
public class MainActivity extends AppCompatActivity
//1.声明控件
private Button bt_Lesson1;
private Button bt_lesson2;
private Button bt_lesson3;
private Button bt_lesson4;
@Override
protected void onCreate(Bundle savedInstanceState) //onCreate用来创建一个activity
super.onCreate(savedInstanceState);
//setContentView方法是在MainActiviy中显示activity_main中所定义的内容
setContentView(R.layout.activity_main);
//2.找到控件
bt_Lesson1 = findViewById(R.id.bt_lesson1);
bt_lesson2 = findViewById(R.id.bt_lesson2);
bt_lesson3 = findViewById(R.id.bt_lesson3);
bt_lesson4 = findViewById(R.id.bt_lesson4);
//4.生成监听器对象

Android Navigation 过渡动画

之前写过一篇。但是没有从很基础开始。。

这有点不太对。那么今天就来一个从很基础开始的教程

效果如下

依赖

    implementation 'androidx.navigation:navigation-fragment-ktx:2.5.1'
    implementation 'androidx.navigation:navigation-ui:2.5.1'

第一个页面

MainActivity

package com.example.shardelement

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.widget.Toast
import androidx.navigation.findNavController
import androidx.navigation.ui.setupActionBarWithNavController

class MainActivity : AppCompatActivity() 
    override fun onCreate(savedInstanceState: Bundle?) 
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        setupActionBarWithNavController(findNavController(R.id.fcv))


    

    override fun onSupportNavigateUp(): Boolean 
        val navController = findNavController(R.id.fcv)
        return navController.navigateUp() || super.onSupportNavigateUp()
    

的布局  

activity_main

<?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">

    <fragment
        android:id="@+id/fcv"
        android:name="androidx.navigation.fragment.NavHostFragment"
        android:layout_width="0dp"
        app:defaultNavHost="true"
        app:navGraph="@navigation/my_nav"
        android:layout_height="0dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

里面很简单 一个Fragment但是里面用到了my_nav。这个会在创建三个fragment后再给大家贴出来 先不要着急

HomeFragment
-》可以跳转FirstFragment 用的是从左边向右边滑动的动画。

-》可以跳转SecondedFragment用的是从右边边向右边滑动的动画。

代码

package com.example.shardelement

import android.os.Bundle
import androidx.fragment.app.Fragment
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.Button
import androidx.navigation.fragment.findNavController


class HomeFragment : Fragment() 

    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? 
        // Inflate the layout for this fragment
        val view = inflater.inflate(R.layout.fragment_home, container, false)
        view.findViewById<Button>(R.id.navToFirst_btn).setOnClickListener 
            findNavController().navigate(R.id.action_homeFragment_to_firstFragment)
        
        view.findViewById<Button>(R.id.navToSecond_btn).setOnClickListener 
            findNavController().navigate(R.id.action_homeFragment_to_seconedFragment)
        
        return view
    

 布局

<?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=".HomeFragment">

    <TextView
        android:id="@+id/homeFragment_txt"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Home Fragment"
        android:textSize="40sp"
        android:textStyle="bold"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/navToFirst_btn"
        android:layout_width="120dp"
        android:layout_height="wrap_content"
        android:layout_marginTop="50dp"
        android:drawableStart="@drawable/ic_baseline_keyboard_arrow_left"
        android:drawableLeft="@drawable/ic_baseline_keyboard_arrow_left"
        android:text="First"
        app:layout_constraintStart_toStartOf="@+id/homeFragment_txt"
        app:layout_constraintTop_toBottomOf="@+id/homeFragment_txt" />

    <Button
        android:id="@+id/navToSecond_btn"
        android:layout_width="120dp"
        android:layout_height="wrap_content"
        android:layout_marginTop="50dp"
        android:drawableEnd="@drawable/ic_baseline_keyboard_arrow_right"
        android:drawableRight="@drawable/ic_baseline_keyboard_arrow_right"
        android:text="Second"
        app:layout_constraintEnd_toEndOf="@+id/homeFragment_txt"
        app:layout_constraintTop_toBottomOf="@+id/homeFragment_txt" />

</androidx.constraintlayout.widget.ConstraintLayout>

 预览

用到了俩左边按钮和右边按钮的icon。。其实。。也可以不放。核心不在此就不贴了

FirstFragment

package com.example.shardelement

import android.os.Bundle
import androidx.fragment.app.Fragment
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.Button
import androidx.navigation.fragment.findNavController


class FirstFragment : Fragment() 

    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? 
        // Inflate the layout for this fragment
        val view = inflater.inflate(R.layout.fragment_first, container, false)
        view.findViewById<Button>(R.id.view_back).setOnClickListener 
            findNavController().navigate(R.id.action_firstFragment_to_homeFragment)
        
        return view
    

布局

<?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"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TextView
        android:id="@+id/tv_tag"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="First Fragment"
        android:textSize="28sp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/view_back"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="20dp"
        android:text="BACK"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/tv_tag" />

</androidx.constraintlayout.widget.ConstraintLayout>

 其实第二个Fragment和他一样。。

真不是为了凑字数。就是为了完整教程来吧

SecondedFragment

package com.example.shardelement

import android.os.Bundle
import androidx.fragment.app.Fragment
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.Button
import androidx.navigation.fragment.findNavController


class SecondedFragment : Fragment() 

    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? 
        // Inflate the layout for this fragment
        val view = inflater.inflate(R.layout.fragment_seconed, container, false)
        view.findViewById<Button>(R.id.view_back).setOnClickListener 
            findNavController().navigate(R.id.action_seconedFragment_to_homeFragment)
        
        return view
    

代码

<?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"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TextView
        android:id="@+id/tv_tag"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Seconded Fragment"
        android:textSize="28sp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/view_back"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="20dp"
        android:text="BACK"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/tv_tag" />

</androidx.constraintlayout.widget.ConstraintLayout>

那么预览我就给一个咯

好

下面是核心。重点 敲黑板

资源文件新建

 my_nav.xml

剩下的我用哔哩哔哩展示把。。为了给大家一个更为骚而快的操作效果。。更详细的效果

下面先贴上去代码。后续看下如何操作的朋友可以看下哔哩哔哩的教学视频哦

<?xml version="1.0" encoding="utf-8"?>
<navigation 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:id="@+id/my_nav.xml"
    app:startDestination="@id/homeFragment">

    <fragment
        android:id="@+id/homeFragment"
        android:name="com.example.shardelement.HomeFragment"
        android:label="fragment_home"
        tools:layout="@layout/fragment_home">

        <action
            android:id="@+id/action_homeFragment_to_firstFragment"
            app:destination="@id/firstFragment"
            app:enterAnim="@anim/from_left"
            app:exitAnim="@anim/to_right"
            app:popEnterAnim="@anim/from_right"
            app:popExitAnim="@anim/to_left" />
        <action
            android:id="@+id/action_homeFragment_to_seconedFragment"

            app:destination="@id/seconedFragment"
            app:enterAnim="@anim/from_right"
            app:exitAnim="@anim/to_left"
            app:popEnterAnim="@anim/from_left"
            app:popExitAnim="@anim/to_right" />
    </fragment>
    <fragment
        android:id="@+id/firstFragment"

        android:name="com.example.shardelement.FirstFragment"
        android:label="FirstFragment">
        <action
            android:id="@+id/action_firstFragment_to_homeFragment"
            app:destination="@id/homeFragment"
            app:enterAnim="@anim/from_right"
            app:exitAnim="@anim/to_left" />
    </fragment>
    <fragment
        android:id="@+id/seconedFragment"
        android:name="com.example.shardelement.SecondedFragment"
        android:label="SeconedFragment">
        <action
            android:id="@+id/action_seconedFragment_to_homeFragment"
            app:destination="@id/homeFragment"
            app:enterAnim="@anim/from_left"
            app:exitAnim="@anim/to_right" />
    </fragment>
</navigation>

from_left.xml

<?xml version="1.0" encoding="utf-8"?>
<set
    android:duration="800"
    xmlns:android="http://schemas.android.com/apk/res/android">
    <translate
        android:fromXDelta="-100%"
        android:toXDelta="0%"
        />
</set>

from_right.xml

<?xml version="1.0" encoding="utf-8"?>
<set
    android:duration="800"
    xmlns:android="http://schemas.android.com/apk/res/android">
    <translate
        android:fromXDelta="100%"
        android:toXDelta="0%"
        />
</set>

to_left.xml

<?xml version="1.0" encoding="utf-8"?>
<set
    android:duration="800"
    xmlns:android="http://schemas.android.com/apk/res/android">
    <translate
        android:fromXDelta="0%"
        android:toXDelta="-100%"
        />
</set>

to_right.xml

<?xml version="1.0" encoding="utf-8"?>
<set
    android:duration="800"
    xmlns:android="http://schemas.android.com/apk/res/android">
    <translate
        android:fromXDelta="0%"
        android:toXDelta="100%"
        />
</set>

哔哩哔哩地址

哔哩哔哩上面有更啰嗦的讲解

视频去哪了呢？_哔哩哔哩_bilibili