标签: kotlin

有没有办法在kotlin中为多个可变变量链接多个let？

fun example(first: String?, second: String?) {
    first?.let {
        second?.let {
            // Do something just if both are != null
        }
    }
}

我的意思是,像这样:

fun example(first: String?, second: String?) {
    first?.let && second?.let { 
        // Do something just if both are != null
    }
}

我刚开始使用Android Studio 3.0.0,但每次尝试构建我的项目时都会收到此错误:

Error:Circular dependency between the following tasks:
:app:compileDebugKotlin
+--- :app:dataBindingExportBuildInfoDebug
|    \--- :app:compileDebugKotlin (*)
\--- :app:kaptDebugKotlin
     \--- :app:dataBindingExportBuildInfoDebug (*)
(*) - details omitted (listed previously)

我在用

kapt "com.android.databinding:compiler:2.2.0"

在我使用之前

androidProcessor "com.android.databinding:compiler:2.2.0"

它工作得很好......我做错了什么？

谢谢!

我正在尝试使用Room Persistence Library的示例.我创建了一个实体:

@Entity
public class Agent {
    @PrimaryKey
    public String guid;
    public String name;
    public String email;
    public String password;
    public String phone;
    public String licence;
}

创建了一个DAO类:

@Dao
public interface AgentDao {
    @Query("SELECT COUNT(*) FROM Agent where email = :email OR phone = :phone OR licence = :licence")
    int agentsCount(String email, String phone, String licence);

    @Insert
    void insertAgent(Agent agent);
}

创建了Database类:

@Database(entities = {Agent.class}, version = 1)
public abstract class AppDatabase extends RoomDatabase {
    public abstract …

我正在尝试使用Kotlin在我的Android应用程序中复制以下ListView:https://github.com/bidrohi/KotlinListView.

不幸的是我收到了一个错误,我无法解决自己.这是我的代码:

MainActivity.kt:

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_main)

    val listView = findViewById(R.id.list) as ListView
    listView.adapter = ListExampleAdapter(this)
}

private class ListExampleAdapter(context: Context) : BaseAdapter() {
    internal var sList = arrayOf("Eins", "Zwei", "Drei")
    private  val mInflator: LayoutInflater

    init {
        this.mInflator = LayoutInflater.from(context)
    }

    override fun getCount(): Int {
        return sList.size
    }

    override fun getItem(position: Int): Any {
        return sList[position]
    }

    override fun getItemId(position: Int): Long {
        return position.toLong()
    }

    override fun getView(position: Int, convertView: View?, …

我在 Flutter 的 Android 部分得到了这个。

Unsupported Java. 
Your build is currently configured to use Java 17.0.2 and Gradle 7.0.2.

Possible solution:
 - Open Gradle wrapper settings, change `distributionUrl` property to use compatible Gradle version and reload the project

请告知解决方案。我真的很感激你的回答。

假设这KeyAdapter是一个抽象类,有几个可以覆盖的方法.

在java中我可以做到:

KeyListener keyListener = new KeyAdapter() {
    @Override public void keyPressed(KeyEvent keyEvent) {
        // ...
    }
};

如何在Kotlin做同样的事情？

如何将我的Kotlin转换Array为varargs Java String[]？

val angularRoutings = 
    arrayOf<String>("/language", "/home")

// this doesn't work        
web.ignoring().antMatchers(angularRoutings)

如何将ArrayList传递给varargs方法参数？

如何在Kotlin中声明辅助构造函数？

有没有关于这方面的文件？

以下不编译......

class C(a : Int) {
  // Secondary constructor
  this(s : String) : this(s.length) { ... }
}

什么区别RequiresApi和TargetApi？

kotlin中的样本:

@RequiresApi(api = Build.VERSION_CODES.M)
@TargetApi(Build.VERSION_CODES.M)
class FingerprintHandlerM() : FingerprintManager.AuthenticationCallback()

注意:FingerprintManager.AuthenticationCallback需要apiM

注2:如果我不使用TargetApi lint失败并出错 class requires api level 23...

我无法从自定义类(Turns)获取泛型类型列表:

val turnsType = TypeToken<List<Turns>>() {}.type
val turns = Gson().fromJson(pref.turns, turnsType)

它说:

cannot access '<init>' it is 'public /*package*/' in 'TypeToken'