小编Ely*_*lye的帖子

在Java中,我们可以执行以下操作

public class TempClass {
    List<Integer> myList = null;
    void doSomething() {
        myList = new ArrayList<>();
        myList.add(10);
        myList.remove(10);
    }
}

但如果我们直接将其重写为Kotlin,如下所示

class TempClass {
    var myList: List<Int>? = null
    fun doSomething() {
        myList = ArrayList<Int>()
        myList!!.add(10)
        myList!!.remove(10)
    }
}

我从我的列表中得到了没有找到add并remove运行的错误

我努力将它转换为ArrayList,但这需要投射它是奇怪的,而在Java中不需要.这就违背了抽象类List的目的

class TempClass {
    var myList: List<Int>? = null
    fun doSomething() {
        myList = ArrayList<Int>()
        (myList!! as ArrayList).add(10)
        (myList!! as ArrayList).remove(10)
    }
}

有没有办法让我使用List但不需要投射它,就像在Java中可以做到的那样？

我在其Manifest中使用了具有以下内容的库.

<application android:allowBackup="true"
    android:label="@string/app_name"
    android:supportsRtl="true"/>

但是,作为我用来包含库的应用程序的反向设置

<application android:allowBackup="false"
    android:label="@string/app_name"
    android:supportsRtl="false"/>

因此它会出现合并错误,如库`Manifest中的`android:supportsRtl ="true"`必不可少？它有时会导致错误

要解决它,我们只需要将以下内容添加到我们的Manifest应用程序中.

tools:replace="android:supportsRtl"

和

tools:replace="android:allowBackup"

但是,添加两个tools:replace将在编译时出错.我怎么能把两者结合起来tools:replace？

我尝试了以下,它不起作用.

tools:replace="android:supportsRtl|android:allowBackup"

当我编译时,我得到了上述错误.我的gradle文件如下: -

apply plugin: 'com.android.application'
apply plugin: 'kotlin-android'
apply plugin: 'kotlin-android-extensions'

android {
    compileSdkVersion 23
    buildToolsVersion "24.0.0 rc2"

    defaultConfig {
        applicationId "package.name"
        minSdkVersion 16
        targetSdkVersion 23
        versionCode 6
        versionName "2.0"
    }

    buildTypes {
        debug {
            minifyEnabled false
            signingConfig signingConfigs.debug
        }
        release {
            minifyEnabled true
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
            signingConfig signingConfigs.release
        }
    }
    sourceSets {
        main.java.srcDirs += 'src/main/kotlin'
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    testCompile 'junit:junit:4.12'
    compile "com.android.support:appcompat-v7:$support_version"
    compile "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version"
    compile "org.jetbrains.anko:anko-sdk15:$anko_version"
    compile "org.jetbrains.anko:anko-support-v4:$anko_version"
    compile "com.android.support:recyclerview-v7:$support_version"
}

buildscript { …

当我运行时pod init，出现以下错误。

RuntimeError - [Xcodeproj] Unknown object version.
/Library/Ruby/Gems/2.6.0/gems/xcodeproj-1.19.0/lib/xcodeproj/project.rb:227:in `initialize_from_file'
/Library/Ruby/Gems/2.6.0/gems/xcodeproj-1.19.0/lib/xcodeproj/project.rb:112:in `open'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.10.1/lib/cocoapods/command/init.rb:41:in `validate!'
/Library/Ruby/Gems/2.6.0/gems/claide-1.0.3/lib/claide/command.rb:333:in `run'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.10.1/lib/cocoapods/command.rb:52:in `run'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.10.1/bin/pod:55:in `<top (required)>'
/usr/local/bin/pod:23:in `load'
/usr/local/bin/pod:23:in `<main>'

从Android Studio 3.0(Canary 5)迁移到Android Studio 3.0(Beta 1)后,移动到最新的gradle,即 'com.android.tools.build:gradle:3.0.0-beta1'

当我尝试gradle sync时,它会在下面显示错误.

Failed to resolve: com.android.support:multidex:1.0.2 
Failed to resolve: com.android.support:multidex-instrumentation:1.0.2 

我检查Android Studio 3.0 Canary 9 - 无法解析包,它不能解决我的问题,因为我已经有了这个

    maven {
        url 'https://maven.google.com'
    }

我很惊讶它甚至要求multidex 1.0.2,因为我只在build.gradle中

compile 'com.android.support:multidex:1.0.1'

我检查使用./gradlew app:dependencies | grep multidex,它显示如下的故障(各种口味等)

+--- com.android.support:multidex-instrumentation:1.0.2 FAILED
+--- com.android.support:multidex:1.0.1
+--- com.android.support:multidex:1.0.2 FAILED
+--- com.android.support:multidex:1.0.1 -> 1.0.2 FAILED

哪儿来的依赖multidex:1.0.2,并multidex-instrumentation:1.0.2从何而来？我怎么能解决这个问题？

我将我的一个Java类转换为Kotlin和类,如下所示.

class MainApplication : Application() {
    companion object {
        operator fun get(context: Context): MainApplication {
            return context.applicationContext as MainApplication
        }
    }
}

它具有静态功能get.

我仍然有一个访问它的Java函数.

MainApplication application = MainApplication.get(mContext);

当MainApplication在Java中时很好.但是当MainApplication在Kotlin中时,上面的代码错误

Error:(27, 54) error: cannot find symbol method get(Context)

我怎样才能访问get上面的Java代码？

我指的是https://developer.android.com/jetpack/compose/state 中的示例。当我编码时

var expanded by remember { mutableStateOf(false) }

它错误说明

Type 'TypeVariable(T)' has no method 'getValue(Nothing?, KProperty<*>)' and thus it cannot serve as a delegate

下面虽然有效

val expanded = remember { mutableStateOf(false) }

// OR

val (expanded, setExpanded) = remember { mutableStateOf(false) }

在 Dagger Hilt View Model 1.0.0-alpha01 中

    implementation "androidx.hilt:hilt-lifecycle-viewmodel:1.0.0-alpha01"
    implementation 'com.google.dagger:hilt-android:2.28-alpha'
    kapt 'androidx.hilt:hilt-compiler:1.0.0-alpha01'
    kapt 'com.google.dagger:hilt-android-compiler:2.28-alpha'

我可以使用下面的

class MyViewModel @ViewModelInject constructor(
    private val repository: Repository,
    @Assisted private val savedStateHandle: SavedStateHandle
) : ViewModel(), LifecycleObserver {

    // Some codes...
}

但是，当我迁移到 Dagger Hilt View Model 1.0.0-alpha03 时

    implementation "androidx.hilt:hilt-lifecycle-viewmodel:1.0.0-alpha03"
    implementation 'com.google.dagger:hilt-android:2.31.2-alpha'
    kapt 'androidx.hilt:hilt-compiler:1.0.0-alpha03'
    kapt 'com.google.dagger:hilt-android-compiler:2.31.2-alpha'

我收到了警告

'Assisted' is deprecated. Deprecated in Java
'ViewModelInject' is deprecated. Deprecated in Java
'ViewModelInject' is deprecated. Deprecated in Java
'Assisted' is deprecated. Deprecated in Java

有什么新的工作方式？

以https://kotlinlang.org/docs/reference/coroutines/flow.html#flows-are-cold的直接例子为例

fun simple(): Flow<Int> = flow { 
    println("Flow started")
    for (i in 1..3) {
        delay(100)
        emit(i)
    }
}

fun main() = runBlocking<Unit> {
    println("Calling simple function...")
    val flow = simple()
    println("Calling collect...")
    flow.collect { value -> println(value) } 
    println("Calling collect again...")
    flow.collect { value -> println(value) } 
}

我得到了错误collect。

This is an internal kotlinx.coroutines API that should not be used from outside of kotlinx.coroutines. No compatibility guarantees are provided.It is recommended to report your use-case of …

我正在使用ConstraintLayout,我将在下面显示

我想隐藏First(使用已消失),以及我期望的视图如下所示(ElasticBody将延伸以使用原始First视图空间).

但是,当我实际设置First为时gone,我的视图结果如下(所有图像都来自Android Studio Design视图).我Elastic Body也失踪了,高度奇怪地扩大了.

我的布局代码如下

<android.support.constraint.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="wrap_content"
    android:padding="16dp">

    <TextView
        android:id="@+id/txt_first"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:background="#0ff"
        android:text="First"
        android:visibility="gone"
        android:textSize="26sp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toStartOf="@+id/txt_body"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/txt_body"
        android:layout_width="0dp"
        android:background="#f0f"
        android:layout_height="wrap_content"
        android:text="Elastic Body"
        android:textSize="26sp"

        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toStartOf="@+id/txt_tail"
        app:layout_constraintStart_toEndOf="@+id/txt_first"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/txt_tail"
        android:background="#ff0"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Tail"
        android:textSize="26sp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toEndOf="@+id/txt_body"
        app:layout_constraintTop_toTopOf="parent" />

</android.support.constraint.ConstraintLayout>

(注意,如果你删除它gone,你将获得第一个图像视图).为什么会这样？我怎么能解决它在我First离开的地方,我可以Elastic Body伸展正确吗？

p/s:我知道如何在LinearLayout和RelativeLayout中做到这一点......但是想知道这是否是对ConstraintLayout的限制？