BufferedReader导致NPE

Question

我正在尝试在手机上安装我的应用程序，并且在运行时我收到以下错误：

错误：

 java.lang.NullPointerException: lock == null
08-11 13:51:59.106 3380-3380/com.example.com.ecoassistant_03 E/AndroidRuntime:     at java.io.Reader.<init>(Reader.java:64)
08-11 13:51:59.106 3380-3380/com.example.com.ecoassistant_03 E/AndroidRuntime:     at java.io.BufferedReader.<init>(BufferedReader.java:107)
08-11 13:51:59.106 3380-3380/com.example.com.ecoassistant_03 E/AndroidRuntime:     at java.io.BufferedReader.<init>(BufferedReader.java:95)
08-11 13:51:59.106 3380-3380/com.example.com.ecoassistant_03 E/AndroidRuntime:     at com.example.com.ecoassistant_03.Populator.populate(Populator.java:38)
08-11 13:51:59.106 3380-3380/com.example.com.ecoassistant_03 E/AndroidRuntime:     at com.example.com.ecoassistant_03.ActMain.onOptionsItemSelected(ActMain.java:1182)
08-11 13:51:59.106 3380-3380/com.example.com.ecoassistant_03 E/AndroidRuntime:     at android.app.Activity.onMenuItemSelected(Activity.java:3205)

码

Populator populate = new Populator();
populate.populate(this, new File(Environment.getExternalStorageDirectory() + "/database/" + "kaAllNodesNumbered.txt"));


public void populate(Context context, File file) {
    this.mCtx = context;
    this.mSQLiteHelper = new SQLiteHelper(this.mCtx);
    //this.mSQLiteHelper.deleteALLRows();
    //Log.i(TAG, "total rows: " + this.mSQLiteHelper.getTotalRowsInDB());

    try {
        this.mFR = new FileReader(file);
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    }
    this.mBR = new BufferedReader(this.mFR); //LINE 38  <<<<=============
    ...
    ...
    ...
}

注意：所需的权限被添加到清单文件和文件“kaAllNodesNumbered.txt”中，路径也是正确的

请帮助我找出错误来自哪里