Question

我是Android的初学者。我正在开发一个应用程序。我收到了这个问题，我不知道该怎么办。

这是我在logcat中收到的：

12-01 11:53:32.485 1509-1509/? D/dalvikvm: Not late-enabling CheckJNI (already on)
12-01 11:53:32.495 1509-1509/? E/Trace: error opening trace file: No such  file or directory (2)
12-01 11:53:32.509 1509-1509/? W/dalvikvm: VFY: unable to find class    referenced in signature (Landroid/view/SearchEvent;)
12-01 11:53:32.509 1509-1509/? I/dalvikvm: Could not find method android.view.Window$Callback.onSearchRequested, referenced from method android.support.v7.view.WindowCallbackWrapper.onSearchRequested
12-01 11:53:32.509 1509-1509/? W/dalvikvm: VFY: unable to resolve interface method 17962: Landroid/view/Window$Callback;.onSearchRequested (Landroid/view/SearchEvent;)Z
12-01 11:53:32.509 1509-1509/? D/dalvikvm: VFY: replacing opcode 0x72 at 0x0002
12-01 11:53:32.509 1509-1509/? I/dalvikvm: Could not find method android.view.Window$Callback.onWindowStartingActionMode, referenced from method android.support.v7.view.WindowCallbackWrapper.onWindowStartingActionMode
12-01 11:53:32.509 1509-1509/? W/dalvikvm: VFY: unable to resolve interface method 17966: Landroid/view/Window$Callback;.onWindowStartingActionMode (Landroid/view/ActionMode$Callback;I)Landroid/view/ActionMode;
12-01 11:53:32.509 1509-1509/? D/dalvikvm: VFY: replacing opcode 0x72 at 0x0002
12-01 11:53:32.515 1509-1509/? I/dalvikvm: Could not find method android.content.res.Resources.getDrawable, referenced from method android.support.v7.widget.ResourcesWrapper.getDrawable
12-01 11:53:32.515 1509-1509/? W/dalvikvm: VFY: unable to resolve virtual method 385: Landroid/content/res/Resources;.getDrawable (ILandroid/content/res/Resources$Theme;)Landroid/graphics/drawable/Drawable;
12-01 11:53:32.515 1509-1509/? D/dalvikvm: VFY: replacing opcode 0x6e at 0x0002
12-01 11:53:32.515 1509-1509/? I/dalvikvm: Could not find method android.content.res.Resources.getDrawableForDensity, referenced from method android.support.v7.widget.ResourcesWrapper.getDrawableForDensity
12-01 11:53:32.515 1509-1509/? W/dalvikvm: VFY: unable to resolve virtual method 387: Landroid/content/res/Resources;.getDrawableForDensity (IILandroid/content/res/Resources$Theme;)Landroid/graphics/drawable/Drawable;
12-01 11:53:32.515 1509-1509/? D/dalvikvm: VFY: replacing opcode 0x6e at 0x0002
12-01 11:53:32.526 1509-1509/? D/AndroidRuntime: Shutting down VM
12-01 11:53:32.526 1509-1509/? W/dalvikvm: threadid=1: thread exiting with uncaught exception (group=0xb4f5a288)
12-01 11:53:32.526 1509-1509/? E/AndroidRuntime: FATAL EXCEPTION: main
                                             java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.mouna.androidproject/com.example.mouna.androidproject.MainActivity}: java.lang.NullPointerException
                                                 at     android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2059)
                                                 at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
                                                 at android.app.ActivityThread.access$600(ActivityThread.java:130)
                                                 at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
                                                 at android.os.Handler.dispatchMessage(Handler.java:99)
                                                 at android.os.Looper.loop(Looper.java:137)
                                                 at android.app.ActivityThread.main(ActivityThread.java:4745)
                                                 at java.lang.reflect.Method.invokeNative(Native Method)
                                                 at java.lang.reflect.Method.invoke(Method.java:511)
                                                 at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
                                                 at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
                                                 at dalvik.system.NativeStart.main(Native Method)
                                              Caused by:  java.lang.NullPointerException
                                                 at com.example.mouna.androidproject.MainActivity.onCreate(MainActivity.java:25)
                                                 at android.app.Activity.performCreate(Activity.java:5008)
                                                 at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079)
                                                 at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2023)
                                                 at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084) 
                                                 at android.app.ActivityThread.access$600(ActivityThread.java:130) 
                                                 at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195) 
                                                 at android.os.Handler.dispatchMessage(Handler.java:99) 
                                                 at android.os.Looper.loop(Looper.java:137) 
                                                 at android.app.ActivityThread.main(ActivityThread.java:4745) 
                                                 at java.lang.reflect.Method.invokeNative(Native Method) 
                                                 at java.lang.reflect.Method.invoke(Method.java:511) 
                                                 at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786) 
                                                 at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553) 
                                                 at dalvik.system.NativeStart.main(Native Method) 
12-01 11:53:53.896 1509-1509/? I/Process: Sending signal. PID: 1509 SIG: 9

这是

这是MainActivity.java：包com.example.mouna.androidproject;

import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.Button;
import android.widget.EditText;

public class MainActivity extends AppCompatActivity implements       View.OnClickListener {
Button bLogout;
EditText etUsername, etAge,etName;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    etUsername = (EditText)findViewById(R.id.etUsername);
    etName = (EditText)findViewById(R.id.etUsername);
    etAge = (EditText)findViewById(R.id.etUsername);
    bLogout=(Button)findViewById(R.id.bLogin);
    bLogout.setOnClickListener(this);}



    @Override
public void onClick(View v) {
    switch(v.getId()){

        case R.id.bLogin:
            break;

    }}}
 and this `<?xml version="1.0" encoding="utf-8"?>
  <manifest xmlns:android="http://schemas.android.com/apk/res/android"
  package="com.example.mouna.androidproject">

<application
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:supportsRtl="true"
    android:theme="@style/AppTheme">
    <activity
        android:name=".MainActivity"
        android:label="@string/app_name"
        android:theme="@style/AppTheme.NoActionBar">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
    <activity
        android:name=".Login"
        android:label="@string/title_activity_login"
        android:theme="@style/AppTheme.NoActionBar" />
    <activity
        android:name=".Register"
        android:label="@string/title_activity_register"
        android:theme="@style/AppTheme.NoActionBar"></activity>
</application>

</manifest>

` 这是Register.java：

 package com.example.mouna.androidproject;

 import android.os.Bundle;
  import android.support.design.widget.FloatingActionButton;
  import android.support.design.widget.Snackbar;
  import android.support.v7.app.AppCompatActivity;
  import android.support.v7.widget.Toolbar;
   import android.view.View;
  import android.widget.Button;
  import android.widget.EditText;

  public class Register extends AppCompatActivity implements  View.OnClickListener {
  Button bRegister;
  EditText etUsername, etName, etPassword, etAge;

  @Override
   protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_register);
    etUsername = (EditText) findViewById(R.id.etUsername);
    etName = (EditText) findViewById(R.id.etUsername);
    etPassword = (EditText) findViewById(R.id.etUsername);
    etAge = (EditText) findViewById(R.id.etUsername);
    bRegister = (Button) findViewById(R.id.bRegister);
    bRegister.setOnClickListener(this);

  }

   @Override
  public void onClick(View v) {
    switch (v.getId()) {

        case R.id.bRegister:
            break;

    }
     }
    }'

Answer 1

看起来您的 MainActivity 无法从您的布局中找到bLogout按钮。检查您的布局文件。必须有 bLogin ID的按钮。

Answer 2

堆栈跟踪的重要部分是：

public class javaapplication24 {

    public static void main(String[] args) {
        int[][] table = new int[10][10];
        int i,j,k;
        for(i=0;i<table.length;i++){
            for(j=0;j<table.length;j++){
                System.out.print(table[i][j]+" ");
            }
            System.out.println();
        }
    }
}

这意味着在MainActivity.java文件的第25行，您可以访问null变量的成员。

AndroidRuntime：FATAL EXCEPTION：主要

2 个答案: