如果我添加片段,我可以删除片段。但是我没有片段时单击了“删除片段”按钮,崩溃了。但这应该给我吐司信息。 我在Logcat中收到此错误消息:
019-08-23 16:38:14.239 3951-3951/com.example.fragment E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.fragment, PID: 3951
java.lang.IllegalStateException: Could not execute method for android:onClick
at androidx.appcompat.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:390)
at android.view.View.performClick(View.java:6597)
at android.view.View.performClickInternal(View.java:6574)
at android.view.View.access$3100(View.java:778)
at android.view.View$PerformClick.run(View.java:25885)
at android.os.Handler.handleCallback(Handler.java:873)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:193)
at android.app.ActivityThread.main(ActivityThread.java:6680)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)
Caused by: java.lang.reflect.InvocationTargetException
at java.lang.reflect.Method.invoke(Native Method)
at androidx.appcompat.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:385)
at android.view.View.performClick(View.java:6597)
at android.view.View.performClickInternal(View.java:6574)
at android.view.View.access$3100(View.java:778)
at android.view.View$PerformClick.run(View.java:25885)
at android.os.Handler.handleCallback(Handler.java:873)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:193)
at android.app.ActivityThread.main(ActivityThread.java:6680)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)
Caused by: kotlin.TypeCastException: null cannot be cast to non-null type com.example.fragment.FragmentA
at com.example.fragment.MainActivity.removeFragmentA(MainActivity.kt:47)
at java.lang.reflect.Method.invoke(Native Method)
at androidx.appcompat.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:385)
at android.view.View.performClick(View.java:6597)
at android.view.View.performClickInternal(View.java:6574)
at android.view.View.access$3100(View.java:778)
at android.view.View$PerformClick.run(View.java:25885)
at android.os.Handler.handleCallback(Handler.java:873)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:193)
at android.app.ActivityThread.main(ActivityThread.java:6680)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)
fun removeFragmentA(v: View) {
val fragmentA = manager.findFragmentByTag("FragA") as FragmentA
val transaction = manager.beginTransaction()
if (fragmentA != null) {
transaction.remove(fragmentA)
transaction.commit()
} else {
Toast.makeText(this, "Fragment A bulunamadı", Toast.LENGTH_LONG).show()
}
}
这是我的删除片段功能:
fun removeFragmentA(v: View) {
val fragmentA = manager.findFragmentByTag("FragA") as FragmentA
val transaction = manager.beginTransaction()
if (fragmentA != null) {
transaction.remove(fragmentA)
transaction.commit()
} else {
Toast.makeText(this, "Fragment A bulunamadı", Toast.LENGTH_LONG).show()
}
}
这是我的xml:
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="ÇIKAR A"
android:onClick="removeFragmentA"/>
我认为问题是那个错误:
由以下原因引起:
kotlin.TypeCastException
:不能将null强制转换为非null类型com.example.fragment.FragmentA
但是我找不到任何解决方案。
答案 0 :(得分:2)
好的,我解决了这个问题。 :)
应该是:
val fragmentA = manager.findFragmentByTag("FragA") as FragmentA?
代替
val fragmentA = manager.findFragmentByTag("FragA") as FragmentA