blocks|key|970594|text|我也有同样的问题，这个解决方案对我来说是有效的。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|970595|使用Java版本从android/app/src/main/kotlin+android/app/src/main/java|970596|Replace++MainActivity.kt+(任意名称)移动文件夹com.example.test_app，或在此复制|unordered-list-item|970597|970598|包com.example.test_app；导入androidx.annotation.NonNull；导入io.flutter.embedding.android.FlutterActivity；导入io.flutter.embedding.engine.FlutterEngine；导入io.flutter.plugins.GeneratedPluginRegistrant；公共类MainActivity扩展FlutterActivity+{@覆盖公共空configureFlutterEngine(@NonNull+flutterEngine)+{非空FlutterEngine+flutterEngine}|970599|删除以下代码:+android/app/build.grandle|970600|970601|..。应用插件：'kotlin-android‘.sourceSets+{+main.java.srcDirs+%2B=+'src/main/kotlin‘}|970602|替换如下：|970603|970604|依赖性{实现"org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version“testImplementation+'junit:junit:4.12‘androidTestImplementation+'androidx.test:runner:1.1.0’androidTestImplementation+'androidx.test.espresso:espresso-core:3.1.0‘}|970605|至|970606|依赖关系{+testImplementation+'junit:junit:4.12‘androidTestImplementation+'com.android.support.test:runner:1.0.2’androidTestImplementation+}|970607|entityMap^0|0|0|0|0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Z|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|10|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|11|8|@]|9|@]|A|$]]|$1|G|3|-4|5|6|7|12|8|@]|9|@]|A|$]]|$1|H|3|I|5|6|7|13|8|@]|9|@]|A|$]]|$1|J|3|K|5|F|7|14|8|@]|9|@]|A|$]]|$1|L|3|-4|5|6|7|15|8|@]|9|@]|A|$]]|$1|M|3|N|5|6|7|16|8|@]|9|@]|A|$]]|$1|O|3|P|5|F|7|17|8|@]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|18|8|@]|9|@]|A|$]]|$1|R|3|S|5|6|7|19|8|@]|9|@]|A|$]]|$1|T|3|U|5|6|7|1A|8|@]|9|@]|A|$]]|$1|V|3|W|5|6|7|1B|8|@]|9|@]|A|$]]|$1|X|3|-4|5|6|7|1C|8|@]|9|@]|A|$]]]|Y|$]]

I had the same problem, for me this solution works. 

<ol>
<li>Move folder com.example.test_app (any name you have) from android/app/src/main/kotlin -> android/app/src/main/java</li>
<li>Replace MainActivity.kt with Java version, or copy down here

<pre><code>package com.example.test_app;

import androidx.annotation.NonNull;
import io.flutter.embedding.android.FlutterActivity;
import io.flutter.embedding.engine.FlutterEngine;
import io.flutter.plugins.GeneratedPluginRegistrant;

public class MainActivity extends FlutterActivity {
 @Override
 public void configureFlutterEngine(@NonNull FlutterEngine flutterEngine) {
 GeneratedPluginRegistrant.registerWith(flutterEngine);
 }
}
</code></pre></li>
<li>Remove following code android/app/build.grandle

<pre><code>...
apply plugin: 'kotlin-android'
...
sourceSets {
 main.java.srcDirs += 'src/main/kotlin'
}
</code></pre></li>
<li>In the same place replace following:

<pre><code>dependencies {
 implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
 testImplementation 'junit:junit:4.12'
 androidTestImplementation 'androidx.test:runner:1.1.0'
 androidTestImplementation 'androidx.test.espresso:espresso-core:3.1.0'
}
</code></pre>

to

<pre><code>dependencies {
 testImplementation 'junit:junit:4.12'
 androidTestImplementation 'com.android.support.test:runner:1.0.2'
 androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
}
</code></pre></li>
</ol>

blocks|key|1904493|text|默认情况下，flutter模板支持使用Kotlin编写Android代码，或者使用Swift编写iOS代码。要使用Java或Objective，请使用-i和/或-a标志：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1904494|在终端运行：flutter+create+-i+objc+-a+java+your_project_name。|offset|length|style|CODE|1904495|如果你想改变你现有的应用程序平台语言选择，作为一种解决办法，你可以删除android/目录并运行来重新创建目录，以便为新的语言选择重新创建目录(+ios/和Swift也一样)。不过，您需要重新应用自定义更改。|BOLD|1904496|entityMap^0|0|6|1C|0|E|6|X|C|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|N|8|@$D|O|E|P|F|G]]|9|@]|A|$]]|$1|H|3|I|5|6|7|Q|8|@$D|R|E|S|F|J]|$D|T|E|U|F|J]]|9|@]|A|$]]|$1|K|3|-4|5|6|7|V|8|@]|9|@]|A|$]]]|L|$]]

By default flutter template supports writing Android code using Kotlin, or iOS code using Swift. To use Java or Objective-C, use the -i and/or -a flags:

In a terminal run: <code>flutter create -i objc -a java your_project_name</code>.

If you wanna change your existing app platform language choice, as a workaround you can delete the android/ directory and run <code>flutter create -a java</code> to get the directory re-created for the new language choice (same for ios/ and Swift).
You need to re-apply custom changes though.

blocks|key|2049938|text|在项目目录中运行flutter+create+-a+java+.|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2049939|2049940|颤振创建:如果在已经存在的项目上运行，这将修复项目，重新创建任何丢失的文件。|blockquote|2049941|2049942|2049943|如果仅由生成的示例代码组成，则删除android/src/main中的android/src/main目录|2049944|entityMap^0|8|O|0|0|0|0|0|H|G|Z|G|0^^$0|@$1|2|3|4|5|6|7|P|8|@$9|Q|A|R|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|S|8|@]|D|@]|E|$]]|$1|G|3|H|5|I|7|T|8|@]|D|@]|E|$]]|$1|J|3|-4|5|6|7|U|8|@]|D|@]|E|$]]|$1|K|3|-4|5|6|7|V|8|@]|D|@]|E|$]]|$1|L|3|M|5|6|7|W|8|@$9|X|A|Y|B|C]|$9|Z|A|10|B|C]]|D|@]|E|$]]|$1|N|3|-4|5|6|7|11|8|@]|D|@]|E|$]]]|O|$]]

run <code>flutter create -a java .</code> inside your project directory 

<blockquote>
 flutter create: If run on a project that already exists, this will
 repair the project, recreating any files that are missing.
</blockquote>

delete the <code>kotlin</code> directory in <code>android/src/main</code> if it only consists of the generated example code

blocks|key|1904575|text|我只想继续这样做，因为今天我不得不将颤音项目中的默认语言从Kotlin更改为Java，并遇到了一点痛苦，在这里，我发现在我的项目目录中运行flutter+create+-i+swift+-a+java+.是有效的，但是会导致我的项目名称根据它所在的任何目录更改，如果目录名是我的“包名”(即:+com.flutter.app和目录是"app")的最后一个值，那么编译时会抛出一个D8:+Program+type+already+present:错误。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1904576|这要归功于原来Kotlin+src的MainActivity。我发现我必须(将源代码签入我想要在包名中使用的"app“文件夹中)，首先删除这个现有的android/app/src/main/kotlin文件夹，然后运行flutter+create+-i+swift+-a+java+.命令。|1904577|注意，我没有将任何唯一的代码添加到Kotlin文件夹中，因此删除该文件夹并不重要。|1904578|希望这能帮助其他遇到类似问题的人。|1904579|entityMap^0|1X|X|59|X|0|22|R|31|X|0|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@$9|O|A|P|B|C]|$9|Q|A|R|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|S|8|@$9|T|A|U|B|C]|$9|V|A|W|B|C]]|D|@]|E|$]]|$1|H|3|I|5|6|7|X|8|@]|D|@]|E|$]]|$1|J|3|K|5|6|7|Y|8|@]|D|@]|E|$]]|$1|L|3|-4|5|6|7|Z|8|@]|D|@]|E|$]]]|M|$]]

Just wanted to follow up with this, as I had to change the default language in my Flutter project from Kotlin to Java today, and ran into a little pain point, where I found that running <code>flutter create -i swift -a java .</code> in my project directory worked, but was causing my project name to change based on whatever directory it was in, and if that directory name was the last value of my "package name" (ie: com.flutter.app and the directory was "app"), this was then throwing a <code>D8: Program type already present:</code> error when compiling.

This is due to the MainActivity of the original Kotlin src. What I discovered is that I had to (after checking out my source code into this "app" folder that I wanted to use in the package name), first delete this existing <code>android/app/src/main/kotlin</code> folder AND THEN run the <code>flutter create -i swift -a java .</code> command.

Note that I didn't have any unique code added to the Kotlin folder, so removal of this folder wasn't a concern.

Hope this helps anyone else experiencing a similar issue.

blocks|key|1904606|text|如果您要从cmd创建一个新项目：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1904607|flutter+create+-i+objc+-a+java+project_name|offset|length|style|CODE|1904608|注意：-a表示android标志，-i表示ios标志。如果您只想使用java，可以删除-i+objc。|1904609|如果要转换现有项目：|1904610|flutter+create+-a+java+.|1904611|在转换现有的项目时，在上面一行的末尾有一个点|BOLD|1904612|entityMap^0|0|0|17|0|17|7|0|0|0|O|0|0|8|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|T|8|@$D|U|E|V|F|G]]|9|@]|A|$]]|$1|H|3|I|5|6|7|W|8|@$D|X|E|Y|F|G]]|9|@]|A|$]]|$1|J|3|K|5|6|7|Z|8|@]|9|@]|A|$]]|$1|L|3|M|5|6|7|10|8|@$D|11|E|12|F|G]]|9|@]|A|$]]|$1|N|3|O|5|6|7|13|8|@$D|14|E|15|F|P]]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|16|8|@]|9|@]|A|$]]]|R|$]]

If you are creating a new project from cmd:
<code>flutter create -i objc -a java project_name</code>
Note: -a means android flag and -i means ios flag. If you want just for java, you can remove <code>-i objc</code>
If you want to convert an existing project:
<code>flutter create -a java .</code>
There is a dot at the end of the above line, when converting an existing project

blocks|key|1904645|text|在尝试执行this和this之后，您会发现无法生成java类、建议和导航声明，等等。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1904646|右键单击java文件夹，将目录标记为>+Source。然后，通过选择android目录打开新的android+studio窗口来编辑java类。|style|CODE|1904647|参考资料：Why+Android+Studio+doesn't+allow+me+to+create+Java+Classes?|1904648|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/a/63197495/7199821|1|https://stackoverflow.com/a/58602076/7199821|2|https://stackoverflow.com/questions/20588040/why-android-studio-doesnt-allow-me-to-create-java-classes^0|5|4|0|A|4|1|0|Y|7|0|5|1N|2|0^^$0|@$1|2|3|4|5|6|7|V|8|@]|9|@$A|W|B|X|1|Y]|$A|Z|B|10|1|11]]|C|$]]|$1|D|3|E|5|6|7|12|8|@$A|13|B|14|F|G]]|9|@]|C|$]]|$1|H|3|I|5|6|7|15|8|@]|9|@$A|16|B|17|1|18]]|C|$]]|$1|J|3|-4|5|6|7|19|8|@]|9|@]|C|$]]]|K|$L|$5|M|N|O|C|$P|Q]]|R|$5|M|N|O|C|$P|S]]|T|$5|M|N|O|C|$P|U]]]]

Just in case after trying to do <a href="https://stackoverflow.com/a/63197495/7199821">this</a> then <a href="https://stackoverflow.com/a/58602076/7199821">this</a>, you found out that you cannot generate java class, suggestion and navigate declaration doesn't appear, etc.,
right click java folder, Mark Directory as &gt; Source root. Then, edit your java class by open new android studio window by choose <code>android</code> directory
reference : <a href="https://stackoverflow.com/questions/20588040/why-android-studio-doesnt-allow-me-to-create-java-classes">Why Android Studio doesn't allow me to create Java Classes?</a>

blocks|key|970768|text|我也在Kotlin+/Flutter上。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|970769|随着最新的Firebase颤振重写，大多数kt文件不再需要。切换到v2嵌入，这并不重要，你使用Kotlin.|970770|https://firebase.flutter.dev/docs/migration/|offset|length|970771|entityMap|0|LINK|mutability|MUTABLE|url^0|0|0|0|18|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|Q|8|@]|9|@$F|R|G|S|1|T]]|A|$]]|$1|H|3|-4|5|6|7|U|8|@]|9|@]|A|$]]]|I|$J|$5|K|L|M|A|$N|E]]]]

I am on Kotlin /Flutter too.
With the latest Firebase Flutter rewrite, most of the kt files are no longer needed. Switch to v2 embedding, and it wont matter you are using Kotlin...
<a href="https://firebase.flutter.dev/docs/migration/" rel="nofollow noreferrer">https://firebase.flutter.dev/docs/migration/</a>

I created a Flutter project using default values, which are Kotlin for Android and Swift for iOS. Halfway through the project I needed to integrate a 3rd party Android SDK that requires Java. Can I convert a Flutter project to Java for Android after creation?

I know I will need yo use Platform Channels to integrate native code with my Flutter app, this is not my concern.

Convert an existing Flutter Kotlin project to Flutter Java project

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

文章

问答

视频

学习中心

腾讯云实验室

直播

竞赛

腾讯云代码分析专区

腾讯iOA零信任安全管理系统专区

腾讯云架构师技术同盟交流圈

腾讯云数据库专区

腾讯云顾问专区

腾讯云原生专区

腾讯混元专区

腾讯云TCE专区

腾讯云Lighthouse专区

腾讯云HAI专区

腾讯云Edgeone专区

腾讯云存储专区

腾讯云智能专区

腾讯轻联专区 

腾讯云开发专区

TAPD专区

腾讯轻量云游戏服专区

腾讯云最具价值专家

腾讯云架构师技术同盟

腾讯云创作之星

腾讯云开发者先锋

腾讯云代码助手

云原生构建

TAPD 敏捷项目管理

Cloud Studio

SDK中心

API中心

命令行工具

涵盖代码开发、场景应用、自动测试全流程，助你从零构建专属AI助手

一站式MCP教程库，解锁AI应用新玩法

我使用默认值创建了一个颤振项目，这两个值分别是安卓的Kotlin和iOS的Swift。在项目进行到一半时，我需要集成一个需要Java的第三方Android。在创建Android之后，我可以将一个颤振项目转换为Java吗？我知道我将需要你使用平台通道将本地代码与我的颤音应用程序集成，这不是我关心的问题。

问将现有的颤振Kotlin项目转换为颤振Java项目
EN

Stack Overflow用户

社区

活动

圈层

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问将现有的颤振Kotlin项目转换为颤振Java项目EN