java.lang.NullPointerException .in files.length i think

Question

please help me.i write this code :

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        File dir=Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS);
        File[] files=dir.listFiles();
        Toast.makeText(this,files.length+"",Toast.LENGTH_LONG).show();

    }
}

and it has this error :

Caused by: java.lang.NullPointerException
    at ir.itpro.videosample.MainActivity.onCreate(MainActivity.java:20)

i put 3 files in directory downloads .

how to fix it now??

`File.listFiles()` can return null, and you aren't checking for it. — user207421, Jul 24 '18 at 22:49

score 0 · Answer 1 · answered Jul 24 '18 at 20:38

0

Make sure you have added the following permission:

READ_EXTERNAL_STORAGE

Also, how are you putting the files in that directory? Through download manager or programmatically?

answered Jul 24 '18 at 20:38

Christian Navarro

380
3
7

score 0 · Answer 2 · answered Jul 24 '18 at 20:48

0

Have you added read external storage permission to your manifest? If not, please add

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

line to it.

If the app don't have the permission, then

dir.listFiles()

returns null, so you call length on a null array.

If your targetSdkVersion is greater than 22, then you need to handle permissions runtime. Further description about runtime permissions can be found here.

answered Jul 24 '18 at 20:48

David Hajas

36
2

Thank u for your help.done – soheil shah Jul 25 '18 at 05:16
I'm glad you could do it. Don't forget to upvote and mark as solution :) – David Hajas Jul 25 '18 at 05:45

java.lang.NullPointerException .in files.length i think

2 Answers2