问是否在其他活动中显示导航抽屉时出现错误？

EN

package com.example.uniapp;

import java.util.ArrayList;

import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.support.v4.app.FragmentTransaction;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;

public class ShowAll extends Description {
MyDatabase MyDataBase;
SQLiteDatabase mydb;
TextView title,content;
ImageView image;


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

    LayoutInflater inflater = (LayoutInflater) this.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    View contentView = inflater.inflate(R.layout.showall, null, false);
    mDrawerLayout.addView(contentView, 0); //null pointer error
  }
}