点击按钮后应用程序停止工作

Question

单击启动屏幕上的"登录"或"注册"按钮后，我的应用程序立即停止工作。

这是我的登录活动：

package com.mypackage.app;
import android.content.Intent;
import android.support.annotation.NonNull;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.Toolbar;
import android.text.TextUtils;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;
import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.Task;
import com.google.firebase.auth.AuthResult;
import com.google.firebase.auth.FirebaseAuth;
import com.rengwuxian.materialedittext.MaterialEditText;
public class LoginActivity extends AppCompatActivity {
MaterialEditText email, password;
Button btn_login;
FirebaseAuth auth;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_login);
Toolbar toolbar = findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
getSupportActionBar().setTitle("Login");
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
auth = FirebaseAuth.getInstance();
email = findViewById(R.id.email);
password = findViewById(R.id.password);
btn_login = findViewById(R.id.btn_login);
btn_login.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
String txt_email = email.getText().toString();
String txt_password = password.getText().toString();
if (TextUtils.isEmpty(txt_email) || TextUtils.isEmpty(txt_password))
{
Toast.makeText(LoginActivity.this, "All fields are required!", Toast.LENGTH_SHORT).show();
}
else
{
auth.signInWithEmailAndPassword(txt_email, txt_password)
.addOnCompleteListener(new OnCompleteListener<AuthResult>() {
@Override
public void onComplete(@NonNull Task<AuthResult> task) {
if (task.isSuccessful())
{
Intent intent = new Intent(LoginActivity.this, MainActivity.class);
intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK | Intent.FLAG_ACTIVITY_NEW_TASK);
startActivity(intent);
finish();
}
else
{
Toast.makeText(LoginActivity.this, "Authentication failed!", Toast.LENGTH_SHORT).show();
}
}
});
}
}
});
}
}

这是开始活动

package com.mypackage.app;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
public class StartActivity extends AppCompatActivity {
Button login, register;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_start);
login = findViewById(R.id.login);
register = findViewById(R.id.register);
login.setOnClickListener(new View.OnClickListener() {
@Override

public void onClick(View view) {
startActivity(new Intent(StartActivity.this, LoginActivity.class));
}
});
register.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
startActivity(new Intent(StartActivity.this, RegisterActivity.class));
}
});
}
}

这是清单文件

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.mypackage.app">
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:roundIcon="@mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="@style/AppTheme">
<activity android:name=".StartActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name=".RegisterActivity"
android:parentActivityName=".StartActivity"/>
<activity android:name=".MainActivity" />
<activity android:name=".LoginActivity"
android:parentActivityName=".StartActivity" />
</application>
</manifest>

我使用的是buildgradle版本3.1.4和谷歌服务版本4.2.0。

依赖项包括：

implementation fileTree(dir: 'libs', include: ['*.jar'])
implementation 'com.android.support:appcompat-v7:28.0.0'
implementation 'com.android.support.constraint:constraint-layout:1.1.3'
implementation 'com.android.support:support-v4:28.0.0'
implementation 'com.android.support:design:28.0.0'
testImplementation 'junit:junit:4.12'
androidTestImplementation 'com.android.support.test:runner:1.0.2'
androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
implementation 'com.google.firebase:firebase-auth:16.0.5'
implementation 'com.google.firebase:firebase-database:16.0.4'
implementation 'com.google.firebase:firebase-storage:16.0.4'
implementation 'com.google.firebase:firebase-core:16.0.4'
implementation 'com.android.support:cardview-v7:28.0.0'
implementation 'com.rengwuxian.materialedittext:library:2.1.4'

当我点击注册按钮时，这是我得到的日志：

11-04 19:38:05.313 2055-2055/com.mypackage.app E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.mypackage.app, PID: 2055
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.mypackage.app/com.mypackage.app.RegisterActivity}: java.lang.ClassCastException: android.widget.Toolbar cannot be cast to android.support.v7.widget.Toolbar
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2779)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2844)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1572)
at android.os.Handler.dispatchMessage(Handler.java:110)
at android.os.Looper.loop(Looper.java:203)
at android.app.ActivityThread.main(ActivityThread.java:6361)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1063)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:924)
Caused by: java.lang.ClassCastException: android.widget.Toolbar cannot be cast to android.support.v7.widget.Toolbar
at com.mypackage.app.RegisterActivity.onCreate(RegisterActivity.java:37)
at android.app.Activity.performCreate(Activity.java:6675)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1119)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2732)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2844) 
at android.app.ActivityThread.-wrap12(ActivityThread.java) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1572) 
at android.os.Handler.dispatchMessage(Handler.java:110) 
at android.os.Looper.loop(Looper.java:203) 
at android.app.ActivityThread.main(ActivityThread.java:6361) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1063) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:924) 

Answer 1

根据您的错误日志，问题与您添加工具栏元素的XML文件有关
从外观上看，你似乎在使用

android.widget.Toolbar

在您的XML中，但在您的java代码中，您正在导入

android.support.v7.widget.Toolbar

这是一种不同的类型。将XML工具栏更改为android.support.v7.widget.toolbar，它应该可以工作了。