Android 按钮 onClick 崩溃

Question

我正在使用 android studios，我只是想通过单击一个简单的按钮来转到另一个活动，但是当我这样做时，我的应用程序每次都会崩溃，我不知道为什么。

这是我在 First_Activity.java 中的代码

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

public class First_Activity  extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.first_activity);

    Button button1 = (Button)findViewById(R.id.button_login);

    button1.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            startActivity(new Intent(First_Activity.this, Second_Activity.class));
        }
    });}

}

这是我在first_activity.xml中的代码

<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".First_Activity">


    <!-- Top image for register page-->
    <!-- Welcome banner for login page-->
    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="69dp"
        android:layout_marginTop="82dp"
        android:layout_marginEnd="67dp"
        android:layout_marginBottom="619dp"
        android:text="@string/login_welcome"
        android:textColor="@color/purple_2"
        android:textSize="22sp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />
    <!-- Prompt to let user know what to do-->
    <TextView
        android:id="@+id/feedbackTextView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="8dp"
        android:text="@string/login_prompt"
        android:textSize="15sp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.498"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView1" />
    <!-- Username bar-->
    <EditText
        android:id="@+id/editTextUsername"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="84dp"
        android:ems="10"
        android:hint="Enter username"
        android:inputType="textPersonName"
        android:textAlignment="center"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.497"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView1" />
    <!-- Password bar with hidden text-->
    <EditText
        android:id="@+id/editTextPassword"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="8dp"
        android:ems="10"
        android:hint="Enter password"
        android:inputType="textPassword"
        android:textAlignment="center"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.497"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/editTextUsername" />
    <!-- Login button-->
    <Button
        android:id="@+id/button_login"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="60dp"
        android:backgroundTint="#2196F3"
        android:onClick="onLoginClick"
        android:text="@string/login_button"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/editTextPassword" />
    <!-- Register button+-->
    <Button
        android:id="@+id/button_create_account"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="4dp"
        android:backgroundTint="#2196F3"
        android:onClick="onCreateAccountClick"
        android:text="@string/create_button"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/button_login" />

</androidx.constraintlayout.widget.ConstraintLayout>

我的代码中也没有看到任何错误，所以我很困惑。

这是我在 Logcat 中的日志（感谢 HovercraftFullOfEels 为我指出了这些崩溃日志）

FATAL EXCEPTION: main
    Process: com.LongDongSilvers.testbed, PID: 17530
    java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.LongDongSilvers.testbed/com.LongDongSilvers.testbed.Second_Activity}: java.lang.ClassCastException: com.LongSongSilvers.testbed.Second_Activity cannot be cast to android.app.Activity
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3551)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3782)
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:101)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2307)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loopOnce(Looper.java:201)
        at android.os.Looper.loop(Looper.java:288)
        at android.app.ActivityThread.main(ActivityThread.java:7872)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:548)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:936)
    Caused by: java.lang.ClassCastException: com.LongDongSilvers.testbed.Second_Activity cannot be cast to android.app.Activity
        at android.app.AppComponentFactory.instantiateActivity(AppComponentFactory.java:95)
        at androidx.core.app.CoreComponentFactory.instantiateActivity(CoreComponentFactory.java:45)
        at android.app.Instrumentation.newActivity(Instrumentation.java:1339)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3538)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3782) 
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:101) 
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135) 
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2307) 
        at android.os.Handler.dispatchMessage(Handler.java:106) 
        at android.os.Looper.loopOnce(Looper.java:201) 
        at android.os.Looper.loop(Looper.java:288) 
        at android.app.ActivityThread.main(ActivityThread.java:7872) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:548) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:936) 

我尝试了多种不同的使用 onClick 的方法，到目前为止，这是最有意义的一种，但还没有骰子。

Answer 1

我可以查看您的错误消息吗？你在Androidmaifest.xml中注册了secondActivity吗？