Question

我有一个自定义的吐司，它在java活动中有效，但在kotlin中不起作用，在kotlin活动中，它引发以下错误：

kotlin.TypeCastException: null cannot be cast to non-null type android.view.ViewGroup

在此行

val layout = inflater.inflate(R.layout.custom_toast,
      findViewById<View>(R.id.custom_toast_container) as ViewGroup)

这是烤面包：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/custom_toast_container"
android:orientation="horizontal"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:padding="8dp"
android:background="@color/colorPrimary"
>
<ImageView android:src="@drawable/ic_done_black_24dp"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginRight="8dp"
    android:tint="@color/colorBackground"
    />
<TextView android:id="@+id/text"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:textColor="#FFF"
    />

我如何在Java中称呼它

LayoutInflater inflater = getLayoutInflater();
View layout = inflater.inflate(R.layout.custom_toast,
(ViewGroup) findViewById(R.id.custom_toast_container));
TextView text = (TextView) layout.findViewById(R.id.text);
text.setText("Already reported");
Toast toast = new Toast(getApplicationContext());
toast.setGravity(Gravity.BOTTOM, 0, 145);
toast.setDuration(Toast.LENGTH_LONG);
toast.setView(layout);
toast.show();

android studio如何将其转换为kotlin：

 val inflater = layoutInflater
 val layout = inflater.inflate(R.layout.custom_toast,
 findViewById<View>(R.id.custom_toast_container) as ViewGroup)

 val text = layout.findViewById<View>(R.id.text) as TextView
 text.text = "Already reported"
 val toast = Toast(context)
 toast.setGravity(Gravity.BOTTOM, 0, 145)
 toast.duration = Toast.LENGTH_LONG
 toast.view = layout
 toast.show()

我在这里做什么错了？

Answer 1

我认为是因为findViewById返回了可为空的值，但您还是想将其强制转换为非null类型。在这里，我对您的代码做了一些修改：

 val inflater = layoutInflater
 val layout = inflater.inflate(R.layout.custom_toast,
 findViewById<View>(R.id.custom_toast_container) as ViewGroup?)

 val text = layout?.findViewById<View>(R.id.text) as TextView?
 text?.text = "Already reported"
 val toast = Toast(context)
 toast.setGravity(Gravity.BOTTOM, 0, 145)
 toast.duration = Toast.LENGTH_LONG
 toast.view = layout
 toast.show()

希望这会对您有所帮助。

Answer 2

Toast.makeText(applicationContext,"this is toast message",Toast.LENGTH_SHORT).show()  

        val toast = Toast.makeText(applicationContext, "Hello Javatpoint", Toast.LENGTH_SHORT)  
        toast.show()  

        val myToast = Toast.makeText(applicationContext,"toast message with gravity",Toast.LENGTH_SHORT)  
        myToast.setGravity(Gravity.LEFT,200,200)  
        myToast.show()

Answer 3

避免findViewById的简便方法

在build.gradle（app）文件中，添加以下行。

apply plugin: 'kotlin-android-extensions'

现在，您可以在.kt文件中编写以下代码。

 val inflater = layoutInflater
        var inflatedFrame = inflater.inflate(R.layout.demo, null)

        inflatedFrame.text.text = "Already reported"

        val toast = Toast(context)
        toast.setGravity(Gravity.BOTTOM, 0, 145)
        toast.duration = Toast.LENGTH_LONG
        toast.view = inflatedFrame
        toast.show()

Toast在Java活动中有效，但在Kotlin中无效

3 个答案: