write permission in Android M

Android M，對於權限管理更要求了，所以要多寫東西才行 :(

zzz

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        /* Request user permissions in runtime */
        ActivityCompat.requestPermissions(MainActivity.this,
            new String[] {
                    Manifest.permission.READ_EXTERNAL_STORAGE,
                    Manifest.permission.WRITE_EXTERNAL_STORAGE
            },
            100);
        /* Request user permissions in runtime */

        String storagePath = Environment.getExternalStorageDirectory().getAbsolutePath();
        String rootPath = storagePath + "/test";
        String fileName = "/test.zip";

        File root = new File(rootPath);
        if(!root.mkdirs()) {
            Log.i("Test", "This path is already exist: " + root.getAbsolutePath());
        }

        File file = new File(rootPath + fileName);
        try {
            int permissionCheck = ContextCompat.checkSelfPermission(MainActivity.this, android.Manifest.permission.WRITE_EXTERNAL_STORAGE);
            if (permissionCheck == PackageManager.PERMISSION_GRANTED) {
                if (!file.createNewFile()) {
                    Log.i("Test", "This file is already exist: " + file.getAbsolutePath());
                }
            }

        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
        switch (requestCode) {
            case 100:
                if (grantResults.length > 0
                        || grantResults[0] == PackageManager.PERMISSION_GRANTED
                        || grantResults[1] == PackageManager.PERMISSION_GRANTED) {
                    /* User checks permission. */

                } else {
                    Toast.makeText(MainActivity.this, "Permission is denied.", Toast.LENGTH_SHORT).show();
                    finish();
                }
                //return; // delete.
        }
    }
}

ref : stackoverflow