Android Studio Web-view permission to access storage? - android-studio

Question

I am developing a Web App with android studio.. I need to have the access open the storage in mobile phone how can I do that?
Here's my manifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.blogspot.httpsmekomik.appmatkomik">
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.CAMERA"/>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<application
android:allowBackup="true"
android:icon="#mipmap/ic_launcher"
android:label="#string/app_name"
android:supportsRtl="true"
android:theme="#style/AppTheme">
<activity
android:name=".MainActivity"
android:screenOrientation="portrait">
</activity>
<activity android:name=".splash">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
MainActivity.java
public class MainActivity extends AppCompatActivity {
private AdView mAdView;
WebView webview;
#Override
public void onBackPressed() {
if (webview.canGoBack()) {
webview.goBack();
} else {
super.onBackPressed();
}
}
#Override
protected void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
OneSignal.startInit(this)
.inFocusDisplaying(OneSignal.OSInFocusDisplayOption.Notification)
.unsubscribeWhenNotificationsAreDisabled(true)
.init();
requestWindowFeature(Window.FEATURE_NO_TITLE);
getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
WindowManager.LayoutParams.FLAG_FULLSCREEN);
setContentView(R.layout.activity_main);
webview = (WebView) findViewById(R.id.webView);
WebSettings webSettings = webview.getSettings();
webSettings.setJavaScriptEnabled(true);
webview.getSettings().setSupportZoom(true);
webview.setWebViewClient(new WebViewClient());
webview.loadUrl("https://mekomik.blogspot.my");
mAdView = (AdView) findViewById(R.id.adView);
AdRequest adRequest = new AdRequest.Builder().build();
mAdView.loadAd(adRequest);
}
}
If require more information from me, please let me know.
I hope you can help me, thanks.