Null Pointer Ausnahme beim Schreiben in die Datei

Question

hey, wenn ich eine Datei erstellen die Protokolle zeigen, dass die Datei erstellt wird, aber es nicht im System existiert, und beim Schreiben in diese Datei sagt Null Zeiger Ausnahme ist da kann mir jemand bitte helfen

try { 
    File root = android.os.Environment.getExternalStorageDirectory(); 
    File dir = new File (root.getAbsolutePath()+ "/Sniffiing"); 
    dir.mkdirs(); 
    File file1 = new File(dir,"dump1.txt"); 
    file1.createNewFile(); 
    System.out.println(file1); 
System.out.println("Hello Buddy what are upto.....##########################"); 
    OutputStreamWriter os = new OutputStreamWriter(
             new FileOutputStream(file1)); 
    bw = new BufferedWriter(os); 
    Process process = Runtime.getRuntime().exec(
             "logcat -v threadtime -s ServiceMode"); 
    int length = process.toString().length(); 

    System.out.println("Length" + length); 

    BufferedReader reader = new BufferedReader(
             new InputStreamReader(process.getInputStream())); 

    StringBuffer output1 = new StringBuffer(); 

    while ((line = reader.readLine()) != null) { 
    bw.write(line); 
    bw.newLine(); 
    } 

} catch (IOException e) { 
} 

hier ist Logcat

D/action: 0 
D/ACTION:: BOTH 
D/Log3GState:: Accessing file 
D/Create file: /data/user/0/com.services.snifspoof.snifspoof/C_packetCapture 
D/Log3GState:: Write executable file 
D/EGL_emulation: eglMakeCurrent: 0x9ef850c0: ver 2 0 (tinfo 0x9ef831f0) 
D/EGL_emulation: eglMakeCurrent: 0x9ef850c0: ver 2 0 (tinfo 0x9ef831f0) 
D/CLOSING: BOTH 
I/System.out: *********############# 
I/System.out: *********############# File Created :- /storage/emulated/0/Sniffing/dump1.txt 
I/System.out: Length34 

      --------- beginning of crash 
E/AndroidRuntime: FATAL EXCEPTION: Thread-2 
Process: com.services.snifspoof.snifspoof, PID: 2389 
java.lang.NullPointerException: Attempt to invoke a virtual method on a null object reference 
at com.services.snifspoof.snifspoof.MainActivity$3$1.run(MainActivity.java:167) 
at java.lang.Thread.run(Thread.java:761) 

Answer 1

Hope this für Sie nützlich sein könnten.

Stellen Sie sicher, dass Sie die Berechtigung zum Lesen von externem Speicher in Ihrer Manifestdatei hinzugefügt haben.

<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" /> 
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" /> 

Datei schreiben:

private void writeToFile(String data,Context context) { 
    try { 
     OutputStreamWriter outputStreamWriter = new OutputStreamWriter(context.openFileOutput("dump1.txt", Context.MODE_PRIVATE)); 
     outputStreamWriter.write(data); 
     outputStreamWriter.close(); 
    } 
    catch (IOException e) { 
     Log.e("Exception", "File write failed: " + e.toString()); 
    } 
} 

Datei lesen:

private String readFromFile(Context context) { 

    String ret = ""; 

    try { 
     InputStream inputStream = context.openFileInput("dump1.txt"); 

     if (inputStream != null) { 
      InputStreamReader inputStreamReader = new InputStreamReader(inputStream); 
      BufferedReader bufferedReader = new BufferedReader(inputStreamReader); 
      String receiveString = ""; 
      StringBuilder stringBuilder = new StringBuilder(); 

      while ((receiveString = bufferedReader.readLine()) != null) { 
       stringBuilder.append(receiveString); 
      } 

      inputStream.close(); 
      ret = stringBuilder.toString(); 
     } 
    } 
    catch (FileNotFoundException e) { 
     Log.e("login activity", "File not found: " + e.toString()); 
    } catch (IOException e) { 
     Log.e("login activity", "Can not read file: " + e.toString()); 
    } 

    return ret; 
}