我不确定为什么我的代码在这里崩溃,我最初认为这是因为我有空的编辑文本,但在实现了一种方法来检查它仍然崩溃。如果将信息放入EditText
,它们就能正常运行。任何想法?
这应该是一个登录页面,如果信息有效,则转到BackgroundWorker
类以确认数据库。我对应用程序开发场景很陌生,所以非常感谢任何帮助。
public class Login extends AppCompatActivity {
EditText emailText, passText, bookIDText;
public static String email;
AlertDialog alertDialog;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_login);
emailText = (EditText) findViewById(R.id.emailTxt);
passText = (EditText) findViewById(R.id.passTxt);
bookIDText = (EditText) findViewById(R.id.bookIDTxt);
Button loginBtn = (Button) findViewById(R.id.LoginBtn);
TextView welcomeText = (TextView) findViewById(R.id.WelcomeToLibrary);
TextView signIn = (TextView) findViewById(R.id.SignInBelow);
TextView clickRegister = (TextView) findViewById(R.id.clickToRegister);
Typeface openSans = Typeface.createFromAsset(getAssets(), "fonts/OpenSans-CondLight.ttf");
welcomeText.setTypeface(openSans);
signIn.setTypeface(openSans);
clickRegister.setTypeface(openSans);
loginBtn.setTypeface(openSans);
}
public void onLogin(View view) {
if (isEmpty(emailText) || isEmpty(passText)) {
alertDialog.setMessage("Please enter all required fields!");
alertDialog.show();
} else {
email = emailText.getText().toString();
String password = passText.getText().toString();
String type = "login";
BackgroundWorker backgroundWorker = new BackgroundWorker(this);
backgroundWorker.execute(type, email, password);
}
}
public void openRegister(View view) {
startActivity(new Intent(this, Register.class));
}
private boolean isEmpty(EditText etText) {
if (etText.getText().toString().trim().length() > 0) {
return false;
} else {
return true;
}
}
}
这是布局
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.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"
android:background="@drawable/blue_background"
tools:context="com.example.hall.pchsmobilelibrary20.Login">
<android.support.constraint.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginBottom="32dp"
android:layout_marginEnd="8dp"
android:layout_marginStart="8dp"
android:background="@drawable/white_rounded_corners"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="0.31">
<TextView
android:id="@+id/WelcomeToLibrary"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginEnd="8dp"
android:layout_marginStart="8dp"
android:layout_marginTop="8dp"
android:text="Welcome to the PCHS Mobile Library!"
android:textAlignment="center"
android:textColor="@android:color/black"
android:textSize="24sp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<EditText
android:id="@+id/emailTxt"
android:layout_width="215dp"
android:layout_height="wrap_content"
android:layout_marginTop="24dp"
android:ems="10"
android:hint="Student/Staff Email"
android:inputType="textWebEmailAddress"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.502"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/SignInBelow" />
<EditText
android:id="@+id/passTxt"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="25dp"
android:ems="10"
android:hint="Password"
android:inputType="textPassword"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/emailTxt" />
<TextView
android:id="@+id/clickToRegister"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginBottom="8dp"
android:layout_marginEnd="8dp"
android:layout_marginStart="8dp"
android:layout_marginTop="8dp"
android:clickable="true"
android:onClick="openRegister"
android:text="Haven't already registered? Click here!"
android:textAlignment="center"
android:textColor="@android:color/black"
android:textSize="18sp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/LoginBtn" />
<Button
android:id="@+id/LoginBtn"
android:layout_width="0dp"
android:layout_height="37dp"
android:layout_marginTop="10dp"
android:background="@drawable/blue_rounded_corners"
android:onClick="onLogin"
android:text="Login"
app:layout_constraintEnd_toEndOf="@+id/passTxt"
app:layout_constraintStart_toStartOf="@+id/passTxt"
app:layout_constraintTop_toBottomOf="@+id/passTxt" />
<TextView
android:id="@+id/SignInBelow"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginEnd="8dp"
android:layout_marginStart="8dp"
android:layout_marginTop="8dp"
android:text="Please Sign In"
android:textAlignment="center"
android:textColor="@android:color/black"
android:textSize="18sp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/WelcomeToLibrary" />
</android.support.constraint.ConstraintLayout>
</android.support.constraint.ConstraintLayout>
错误消息
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.hall.pchsmobilelibrary20, PID: 5172
java.lang.IllegalStateException: Could not execute method for android:onClick
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:293)
at android.view.View.performClick(View.java:6256)
at android.view.View$PerformClick.run(View.java:24701)
at android.os.Handler.handleCallback(Handler.java:789)
at android.os.Handler.dispatchMessage(Handler.java:98)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6541)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)
Caused by: java.lang.reflect.InvocationTargetException
at java.lang.reflect.Method.invoke(Native Method)
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288)
at android.view.View.performClick(View.java:6256)
at android.view.View$PerformClick.run(View.java:24701)
at android.os.Handler.handleCallback(Handler.java:789)
at android.os.Handler.dispatchMessage(Handler.java:98)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6541)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.app.AlertDialog.setMessage(java.lang.CharSequence)' on a null object reference
at com.example.hall.pchsmobilelibrary20.Login.onLogin(Login.java:45)
at java.lang.reflect.Method.invoke(Native Method)
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288)
at android.view.View.performClick(View.java:6256)
at android.view.View$PerformClick.run(View.java:24701)
at android.os.Handler.handleCallback(Handler.java:789)
at android.os.Handler.dispatchMessage(Handler.java:98)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6541)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)
申请已终止。
答案 0 :(得分:0)
请在onCreate()方法
中添加此行alertDialog = new AlertDialog.Builder(this).create();
答案 1 :(得分:0)
bookIDText = (EditText) findViewById(R.id.bookIDTxt);
我认为上面的代码会导致错误,因为您的布局中没有EditText
个名称bookIDTxt
。