当我尝试显示 toast 时添加 onclicklistener 后应用程序崩溃
[英]App crashes as soon as i add onclicklistener when trying to display toast
问题描述
当我尝试添加祝酒词时，我的应用程序崩溃了，我认为我做的一切都是正确的，但也许不是，在长时间休息后试图重新开始编程并遇到像这样的愚蠢问题有什么想法吗？
我在 java 和 kotlin 中编写了相同的代码，但应用程序仍然崩溃
似乎一旦我添加了点击监听器，该应用程序就不再有效
这是代码中的问题还是我的 ide 的问题。
家庭电话 xml：
<?xml version="1.0" encoding="utf-8"?>
<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=".ui.home.HomeFragment">
<TextView
android:id="@+id/text_home"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginStart="8dp"
android:layout_marginTop="8dp"
android:layout_marginEnd="8dp"
android:textAlignment="center"
android:textSize="20sp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintBottom_toBottomOf="parent"/>
<Button
android:text="Button"
android:layout_width="wrap_content"
android:layout_height="wrap_content" android:id="@+id/btnToast"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintBottom_toBottomOf="parent" app:layout_constraintStart_toStartOf="parent"
app:layout_constraintEnd_toEndOf="parent"/>
</androidx.constraintlayout.widget.ConstraintLayout>
主要活动.java：
package com.example.javaapp;
import android.view.View;
import android.widget.Button;
import android.os.Bundle;
import android.widget.Toast;
import com.google.android.material.bottomnavigation.BottomNavigationView;
import androidx.appcompat.app.AppCompatActivity;
import androidx.navigation.NavController;
import androidx.navigation.Navigation;
import androidx.navigation.ui.AppBarConfiguration;
import androidx.navigation.ui.NavigationUI;
import com.example.javaapp.databinding.ActivityMainBinding;
public class MainActivity extends AppCompatActivity {
private ActivityMainBinding binding;
Button btnToast;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
btnToast = findViewById(R.id.btnToast);
btnToast.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Toast.makeText(MainActivity.this,"hello test 123",Toast.LENGTH_LONG).show();
}
});
binding = ActivityMainBinding.inflate(getLayoutInflater());
setContentView(binding.getRoot());
BottomNavigationView navView = findViewById(R.id.nav_view);
// Passing each menu ID as a set of Ids because each
// menu should be considered as top level destinations.
AppBarConfiguration appBarConfiguration = new AppBarConfiguration.Builder(
R.id.navigation_home, R.id.navigation_dashboard, R.id.navigation_notifications)
.build();
NavController navController = Navigation.findNavController(this, R.id.nav_host_fragment_activity_main);
NavigationUI.setupActionBarWithNavController(this, navController, appBarConfiguration);
NavigationUI.setupWithNavController(binding.navView, navController);
}
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2022-12-05 16:36:37.852 18840-18840 Process com.example.javaapp I Sending signal. PID: 18840 SIG: 9
---------------------------- PROCESS ENDED (18840) for package com.example.javaapp ----------------------------
2022-12-05 16:38:07.020 17039-17039 studio.deploy install_server-bde4359e E Could not remove dir '/data/data/com.example.javaapp/code_cache/.ll/': No such file or directory
---------------------------- PROCESS STARTED (19001) for package com.example.javaapp ----------------------------
2022-12-05 16:38:07.581 19001-19001 Compatibil...geReporter com.example.javaapp D Compat change id reported: 171979766; UID 10158; state: ENABLED
2022-12-05 16:38:07.601 19001-19001 ziparchive com.example.javaapp W Unable to open '/data/app/~~FeimdrJdwhN9iQHirqPvHg==/com.example.javaapp-WIltqAi8b9LeodOkfpOG5w==/base.dm': No such file or directory
2022-12-05 16:38:07.601 19001-19001 ziparchive com.example.javaapp W Unable to open '/data/app/~~FeimdrJdwhN9iQHirqPvHg==/com.example.javaapp-WIltqAi8b9LeodOkfpOG5w==/base.dm': No such file or directory
2022-12-05 16:38:07.728 19001-19001 GraphicsEnvironment com.example.javaapp V ANGLE Developer option for 'com.example.javaapp' set to: 'default'
2022-12-05 16:38:07.729 19001-19001 GraphicsEnvironment com.example.javaapp V ANGLE GameManagerService for com.example.javaapp: false
2022-12-05 16:38:07.729 19001-19001 GraphicsEnvironment com.example.javaapp V Neither updatable production driver nor prerelease driver is supported.
2022-12-05 16:38:07.732 19001-19001 NetworkSecurityConfig com.example.javaapp D No Network Security Config specified, using platform default
2022-12-05 16:38:07.733 19001-19001 NetworkSecurityConfig com.example.javaapp D No Network Security Config specified, using platform default
2022-12-05 16:38:07.752 19001-19026 libEGL com.example.javaapp D loaded /vendor/lib64/egl/libEGL_emulation.so
2022-12-05 16:38:07.753 19001-19026 libEGL com.example.javaapp D loaded /vendor/lib64/egl/libGLESv1_CM_emulation.so
2022-12-05 16:38:07.754 19001-19026 libEGL com.example.javaapp D loaded /vendor/lib64/egl/libGLESv2_emulation.so
2022-12-05 16:38:07.806 19001-19001 example.javaapp com.example.javaapp W Accessing hidden method Landroid/view/View;->computeFitSystemWindows(Landroid/graphics/Rect;Landroid/graphics/Rect;)Z (unsupported, reflection, allowed)
2022-12-05 16:38:07.806 19001-19001 example.javaapp com.example.javaapp W Accessing hidden method Landroid/view/ViewGroup;->makeOptionalFitsSystemWindows()V (unsupported, reflection, allowed)
2022-12-05 16:38:07.807 19001-19001 Compatibil...geReporter com.example.javaapp D Compat change id reported: 210923482; UID 10158; state: DISABLED
2022-12-05 16:38:07.807 19001-19001 Compatibil...geReporter com.example.javaapp D Compat change id reported: 37756858; UID 10158; state: ENABLED
2022-12-05 16:38:07.810 19001-19001 AndroidRuntime com.example.javaapp D Shutting down VM
2022-12-05 16:38:07.812 19001-19001 AndroidRuntime com.example.javaapp E FATAL EXCEPTION: main
Process: com.example.javaapp, PID: 19001
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.javaapp/com.example.javaapp.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3676)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3813)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:101)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2308)
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:7898)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:548)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:936)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
at com.example.javaapp.MainActivity.onCreate(MainActivity.java:27)
at android.app.Activity.performCreate(Activity.java:8290)
at android.app.Activity.performCreate(Activity.java:8269)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1384)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3657)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3813)
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$H.handleMessage(ActivityThread.java:2308)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loopOnce(Looper.java:201)
at android.os.Looper.loop(Looper.java:288)
at android.app.ActivityThread.main(ActivityThread.java:7898)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:548)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:936)
2022-12-05 16:38:07.833 19001-19001 Process com.example.javaapp I Sending signal. PID: 19001 SIG: 9
---------------------------- PROCESS ENDED (19001) for package com.example.javaapp ----------------------------
1 个解决方案
解决方案1
0 已采纳 2022-12-05 17:57:27
您在创建布局之前将值分配给 btnToast。
试试这个：
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
binding = ActivityMainBinding.inflate(getLayoutInflater());
setContentView(binding.getRoot());
btnToast = findViewById(R.id.btnToast);
btnToast.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Toast.makeText(MainActivity.this,"hello test 123",Toast.LENGTH_LONG).show();
}
});
将onClickListener添加到ImageView时，应用程序崩溃
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