Android Studio Web视图访问存储的权限？

Question

我正在用android studio开发一个Web应用程序。我需要访问权限才能打开手机中的存储空间，该怎么办？

这是我的 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);
        }
    }

如果需要我提供更多信息，请告诉我。 希望您能帮助我，谢谢。