执行发送凭据无效时，我不断收到错误消息

时间：2019-03-08 01:57:19

标签： android

运行代码时，执行SendCredentials无效时会出错。

错误是：-

  E/AndroidRuntime: FATAL EXCEPTION: main
 Process: com.example.messager, PID: 16131
 java.lang.IllegalStateException: Could not execute method for android:onClick
     at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:390)
     at android.view.View.performClick(View.java:6614)
     at android.view.View.performClickInternal(View.java:6591)
     at android.view.View.access$3100(View.java:786)
     at android.view.View$PerformClick.run(View.java:25948)
     at android.os.Handler.handleCallback(Handler.java:873)
     at android.os.Handler.dispatchMessage(Handler.java:99)
     at android.os.Looper.loop(Looper.java:201)
     at android.app.ActivityThread.main(ActivityThread.java:6806)
     at java.lang.reflect.Method.invoke(Native Method)
     at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:547)
     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:873)
  Caused by: java.lang.reflect.InvocationTargetException
     at java.lang.reflect.Method.invoke(Native Method)
     at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:385)
     at android.view.View.performClick(View.java:6614) 
     at android.view.View.performClickInternal(View.java:6591) 
     at android.view.View.access$3100(View.java:786) 
     at android.view.View$PerformClick.run(View.java:25948) 
     at android.os.Handler.handleCallback(Handler.java:873) 
     at android.os.Handler.dispatchMessage(Handler.java:99) 
     at android.os.Looper.loop(Looper.java:201) 
     at android.app.ActivityThread.main(ActivityThread.java:6806) 
     at java.lang.reflect.Method.invoke(Native Method) 
     at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:547) 
     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:873) 
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.io.DataInputStream.readLine()'
     on a null object reference
     at com.example.messager.MainActivity.SendCredentials(MainActivity.java:69)
     at com.example.messager.MainActivity.SendMessage(MainActivity.java:26)
     at java.lang.reflect.Method.invoke(Native Method) 
     at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:385) 
     at android.view.View.performClick(View.java:6614) 
     at android.view.View.performClickInternal(View.java:6591) 
     at android.view.View.access$3100(View.java:786) 
     at android.view.View$PerformClick.run(View.java:25948) 
     at android.os.Handler.handleCallback(Handler.java:873) 
     at android.os.Handler.dispatchMessage(Handler.java:99) 
     at android.os.Looper.loop(Looper.java:201) 
     at android.app.ActivityThread.main(ActivityThread.java:6806) 
     at java.lang.reflect.Method.invoke(Native Method) 
     at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:547) 
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:873)

我的代码是 

package com.example.messager;

import android.support.design.widget.TextInputLayout;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
import java.net.*;
import java.io.*;

public class MainActivity extends AppCompatActivity {

    EditText stopPort;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }
    public void SendMessage(View view)throws IOException{
        EditText emailText = (EditText) findViewById(R.id.Email);
        String Username = emailText.getText().toString();
        EditText passwordText = (EditText) findViewById(R.id.Password);
        String Password = passwordText.getText().toString();

        System.out.println("Your username is " + Username + "Your Password is " + Password);
        SendCredentials();
    }
    public void SendCredentials()throws IOException {
        System.out.println("Work");
        Socket socket = new Socket("192.168.0.114", 4321);
        System.out.println("Work");
        DataOutputStream dOut = new DataOutputStream(socket.getOutputStream());

        dOut.writeByte(1);
        dOut.writeUTF("This is a test");
        dOut.flush();
        System.out.println("Work");
    }
    public void Check(){



    }
}

`

3 个答案:

答案 0 :(得分：0)

查看上面的代码和异常跟踪2可能是错误的。

  1. 检查您的代码是否 java.lang.NullPointerException：尝试在

    2. 上的空对象引用上调用虚拟方法'java.lang.String java.io.DataInputStream.readLine（）'。

  2. 在xml布局文件中，您是否在android：onClick上声明了“检查”方法 即android：onClick =“ check”，如果是，则您的检查方法应如下所示

公共无效检查（查看）{ }

您是否也可以共享xml布局文件。

答案 1 :(得分：0)

是的，我的xml代码是' 

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=".MainActivity">

    <TextView
        android:id="@+id/Welcome"
        android:layout_width="198dp"
        android:layout_height="52dp"
        android:layout_marginStart="104dp"
        android:layout_marginTop="68dp"
        android:text="Welcome"
        android:textAlignment="center"
        android:textAllCaps="false"
        android:textColor="@color/colorPrimaryDark"
        android:textSize="36sp"
        android:textStyle="bold"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <android.support.design.widget.TextInputLayout
        android:id="@+id/passwordWrapper"
        android:layout_width="387dp"
        android:layout_height="56dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="444dp"
        android:hint="Password"
        app:hintEnabled="true"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent">

        <EditText
            android:id="@+id/Password"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:hint="Password"
            android:inputType="textPassword"
            android:textSize="18sp"
            tools:text="" />
    </android.support.design.widget.TextInputLayout>

    <android.support.design.widget.TextInputLayout
        android:id="@+id/emailWrapper"
        android:layout_width="397dp"
        android:layout_height="56dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="368dp"
        android:hint="Email"
        app:hintEnabled="true"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent">

        <EditText
            android:id="@+id/Email"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:hint="Email"
            android:inputType="textWebEmailAddress"
            android:textAlignment="textStart"
            android:textSize="18sp"
            tools:text=""/>

    </android.support.design.widget.TextInputLayout>

    <Button
        android:id="@+id/LoginButton"
        android:layout_width="348dp"
        android:layout_height="45dp"
        android:layout_marginStart="28dp"
        android:layout_marginTop="520dp"
        android:text="LOGIN"
        android:onClick="SendMessage"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</android.support.constraint.ConstraintLayout>

'

答案 2 :(得分：-1)

public void SendMessage(View view) throws IOException {
    EditText emailText = (EditText) findViewById(R.id.Email);
    String Username = emailText.getText().toString();
    EditText passwordText = (EditText) findViewById(R.id.Password);
    String Password = passwordText.getText().toString();

    System.out.println("Your username is " + Username + "Your Password is " + Password);
    SendCredentials();
}

public void SendCredentials() throws IOException {
    new MyAsyncTask().execute();
}

public void Check() {
}


private class MyAsyncTask extends AsyncTask<Void, Void, Void> {

    Activity activity;
    IOException ioException;

    MyAsyncTask() {
        super();
    }

    @Override
    protected Void doInBackground(Void... voids) {
        StringBuilder sb = new StringBuilder();
        try {
            System.out.println("Work");
            Socket socket = new Socket("192.168.0.114", 4321);
            System.out.println("Work");
            DataOutputStream dOut = new DataOutputStream(socket.getOutputStream());

            dOut.writeByte(1);
            dOut.writeUTF("This is a test");
            dOut.flush();
            System.out.println("Work");

            socket.close();

        } catch (IOException e) {
            this.ioException = e;

        }

}  }

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