Android：NullPointerException 错误

Question

我知道询问 NullPointerException 的答案很无聊，而且还有类似的问题。但是，我只是无法从其他问题中找到解决问题的方法。

我有 2 节课：

1. CreateContactActivityl.java：

将文本输出的意图传递给 RegexOCR1.java

1. 正则表达式OCR1.java：

接收文本输出，将文本输出传递给该类中的方法

如logcat所述，RegexOCR1.java中出现错误：

Fatal Exception: java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.l33902.contactmanagment1512/com.example.l33902.contactmanagment.RegexOCR1}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.os.Bundle.getString(java.lang.String)' on a null object reference
       at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3155)
       at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3263)
       at android.app.ActivityThread.access$1000(ActivityThread.java:197)
       at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1687)
       at android.os.Handler.dispatchMessage(Handler.java:102)
       at android.os.Looper.loop(Looper.java:145)
       at android.app.ActivityThread.main(ActivityThread.java:6897)
       at java.lang.reflect.Method.invoke(Method.java)
       at java.lang.reflect.Method.invoke(Method.java:372)
       at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1404)
       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1199)
Caused by java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.os.Bundle.getString(java.lang.String)' on a null object reference
       at com.example.l33902.contactmanagment.RegexOCR1.onCreate(RegexOCR1.java:32)
       at android.app.Activity.performCreate(Activity.java:6550)
       at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1120)
       at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3108)
       at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3263)
       at android.app.ActivityThread.access$1000(ActivityThread.java:197)
       at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1687)
       at android.os.Handler.dispatchMessage(Handler.java:102)
       at android.os.Looper.loop(Looper.java:145)
       at android.app.ActivityThread.main(ActivityThread.java:6897)
       at java.lang.reflect.Method.invoke(Method.java)
       at java.lang.reflect.Method.invoke(Method.java:372)
       at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1404)
       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1199)

我还实现了用于调试的 Crashlytics，如下面的链接所示：

Crashlytics Results

在CreateContactActivityOCR.java：

以下是将文本输出意图传递给 RegexOCR1.java 的代码

private void passText(){
        //Log.i(TAG, "PassText");
        Intent intent = new Intent(this, RegexOCR1.class);
        startActivity(intent);
    }

在 RegexOCR1.java 中：

下面是我用来接收文本输出然后传入方法EmailValidator()的代码：

public class RegexOCR1 extends Activity {

    private Pattern pattern;
    private Matcher matcher;

    private String recognizedText, textToUse;
    private String mFromLang, mCurrentLang;

    private static final String EMAIL_PATTERN =
            "^[_A-Za-z0-9-\\+]+(\\.[_A-Za-z0-9-]+)*@"
                    + "[A-Za-z0-9-]+(\\.[A-Za-z0-9]+)*(\\.[A-Za-z]{2,})$";

    private static final String PHONE_PATTERN =
            "^[89]\\d{7}$";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);

        // Getting the path of the image from another class
        Bundle extras = this.getIntent().getExtras();
        recognizedText = extras.getString("TEXT");
        textToUse = recognizedText;

        // Getting the language used for text recognition
        mFromLang = extras.getString("LANG");
        mCurrentLang = mFromLang;
        //Log.i(TAG, mFromLang);

        EmailValidator();
    }


    public String EmailValidator() {

        Pattern pattern = Pattern.compile(EMAIL_PATTERN);
        Matcher matcher = pattern.matcher(textToUse);
        if (matcher.find()) {
            String email = textToUse.substring(matcher.start(), matcher.end());

        } else {
            // TODO handle condition when input doesn't have an email address
        }

        return textToUse;
    }

    public boolean validate(final String hex) {

        matcher = pattern.matcher(hex);
        return matcher.matches();

    }

    private void showText(){
        //Log.i(TAG, "ShowText");
        Intent intent = new Intent(this, CreateContactActivityOCR.class);
        startActivity(intent);
    }
} 

我不知道 RegexOCR1.java 中的哪个进程发生了错误。

根据 Crashlytics，它是第 32 行：recognizedText = extras.getString("TEXT");

但是，我在 CreateContactActivityOCR.java 中使用了这一行来收集另一个类的文本输出，没有错误。

Answer 1

private void passText(){
    //Log.i(TAG, "PassText");
    Intent intent = new Intent(this, RegexOCR1.class);
    intent.putExtra("TEXT", "your text here");
    startActivity(intent);
}

Answer 2

尝试以下代码并再次运行

    private void passText(){
    //Log.i(TAG, "PassText");
    Intent intent = new Intent(this, RegexOCR1.class);
    intent.putExtra("TEXT","YOUR STRING DATA");
    intent.putExtra("LANG","YOUR STRING DATA");
    startActivity(intent);
}