응용 프로그램을 다시 시작할 때 NullPointerException 나열

나는 현재 SMS 응용 프로그램을 개발하려고 시도하고 있으며 실행되고 메시지를 검색 할 수 있지만 응용 프로그램을 닫고 다시 시작하면 강제로 닫히고 NullPointerException이 있다고 말합니다. 다음은 오류 로그입니다. 목록이 이유 일 수 있지만 이유를 모르겠습니다. StackOverflow는 추가 정보를 추가하지 않고 게시 할 수 없습니다.

08-08 16:08:17.317 9977-9977/backdev.messages E/AndroidRuntime: FATAL EXCEPTION: main
                                                            Process: backdev.messages, PID: 9977
                                                            java.lang.RuntimeException: Unable to start activity ComponentInfo{backdev.messages/backdev.messages.MessageActivity}: java.lang.NullPointerException: Attempt to invoke interface method 'boolean java.util.List.add(java.lang.Object)' on a null object reference
                                                                at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2434)
                                                                at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2494)
                                                                at android.app.ActivityThread.access$900(ActivityThread.java:153)
                                                                at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1347)
                                                                at android.os.Handler.dispatchMessage(Handler.java:102)
                                                                at android.os.Looper.loop(Looper.java:148)
                                                                at android.app.ActivityThread.main(ActivityThread.java:5451)
                                                                at java.lang.reflect.Method.invoke(Native Method)
                                                                at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
                                                                at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
                                                             Caused by: java.lang.NullPointerException: Attempt to invoke interface method 'boolean java.util.List.add(java.lang.Object)' on a null object reference
                                                                at backdev.messages.MessageActivity.refreshSMSInbox(MessageActivity.java:136)
                                                                at backdev.messages.MessageActivity.getPermissionToReadSMS(MessageActivity.java:118)
                                                                at backdev.messages.MessageActivity.onCreate(MessageActivity.java:78)
                                                                at android.app.Activity.performCreate(Activity.java:6323)
                                                                at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1108)
                                                                at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2387)
                                                                at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2494) 
                                                                at android.app.ActivityThread.access$900(ActivityThread.java:153) 
                                                                at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1347) 
                                                                at android.os.Handler.dispatchMessage(Handler.java:102) 
                                                                at android.os.Looper.loop(Looper.java:148) 
                                                                at android.app.ActivityThread.main(ActivityThread.java:5451) 
                                                                at java.lang.reflect.Method.invoke(Native Method) 
                                                                at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
                                                                at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 

내 코드는 다음과 같습니다.

private static final int READ_SMS_PERMISSIONS_REQUEST =1;
private Context mContext = MessageActivity.this;
private static final String TAG = "MessageActivity";

private List<PreviewMessage> mPreviewMessages;
private RecyclerView rvMessages;
private static MessageActivity inst;
private RecyclerView.Adapter mMessagesAdapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_message);

    rvMessages = (RecyclerView) findViewById(R.id.rvMessages);
    rvMessages.setHasFixedSize(true);
    rvMessages.setLayoutManager(new LinearLayoutManager(mContext));

    getPermissionToReadSMS();
    mPreviewMessages = new ArrayList<>();
    if (ContextCompat.checkSelfPermission(this, Manifest.permission.READ_SMS)
            != PackageManager.PERMISSION_GRANTED) {
        getPermissionToReadSMS();
    } else {
        refreshSMSInbox();
    }

}

public void getPermissionToReadSMS(){
    Log.d(TAG, "getPermissionToReadSMS: getting permission");
    if(ContextCompat.checkSelfPermission(mContext, Manifest.permission.READ_SMS)!= PackageManager.PERMISSION_GRANTED){
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            // Should we show an explanation?
            if (shouldShowRequestPermissionRationale(Manifest.permission.READ_SMS)){
                Log.d(TAG, "getPermissionToReadSMS: requesting Permission again");
                // Show an explanation to the user *asynchronously* -- don't block
                // this thread waiting for the user's response! After the user
                // sees the explanation, try again to request the permission.
                Toast.makeText(mContext,"Application will not work without this permission", Toast.LENGTH_SHORT).show();

                requestPermissions(new String[]{Manifest.permission.READ_SMS},READ_SMS_PERMISSIONS_REQUEST);
            }
            // No explanation needed, we can request the permission.
            //display explanation first --- not yet done
            Log.d(TAG, "getPermissionToReadSMS: requestPermission");
            requestPermissions(new String[]{Manifest.permission.READ_SMS},READ_SMS_PERMISSIONS_REQUEST);
        }
    }else{
            refreshSMSInbox();

    }

}

private void refreshSMSInbox() {
    ContentResolver contentResolver = getContentResolver();
    Cursor smsInboxCursor = contentResolver.query(Uri.parse("content://sms/inbox"),null,null,null,null);
    int indexBody = smsInboxCursor.getColumnIndex("body");
    int indexAddress = smsInboxCursor.getColumnIndex("address");
    while (smsInboxCursor.moveToNext()) {

        PreviewMessage previewMessage = new PreviewMessage(smsInboxCursor.getString(indexAddress),smsInboxCursor.getString(indexBody),  1);

        /*
        ERROR HERE
         */
        mPreviewMessages.add(previewMessage);

    }

    mMessagesAdapter = new MessagesAdapter(mPreviewMessages,mContext);

    rvMessages.setAdapter(mMessagesAdapter);
}
@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
    super.onRequestPermissionsResult(requestCode, permissions, grantResults);
    switch (requestCode){
        case 1:
            // If request is cancelled, the result arrays are empty.
            if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED){
                //granted do things here
                //read sms
                refreshSMSInbox();

            }else {

            }
    }
}