Web视图中的上传文件无效

Question

老实说我只是想创建一个应用程序来查看网站我不是android developer.inside这个网站有一个上传文件图像文件的选项，它不起作用任何人请告诉我什么继续这是我的java类

package com.example.median1.psalmsmarket;

import android.net.Uri;
import android.os.Build;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.webkit.CookieManager;
import android.webkit.ValueCallback;
import android.webkit.WebSettings;
import android.webkit.WebView;
import android.webkit.WebViewClient;
import android.app.ProgressDialog;

import com.google.android.gms.ads.AdRequest;
import com.google.android.gms.ads.AdSize;
import com.google.android.gms.ads.AdView;
import com.google.android.gms.ads.MobileAds;
import com.onesignal.OneSignal;

public class Psalms extends AppCompatActivity {
    AdView mAdview;

    WebView webview;

    private ValueCallback<Uri> mUploadMessage;
    private final static int FILECHOOSER_RESULTCODE = 1;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        OneSignal.startInit(this)
                .inFocusDisplaying(OneSignal.OSInFocusDisplayOption.Notification)
                .unsubscribeWhenNotificationsAreDisabled(true)
                .init();
        setContentView(R.layout.activity_psalms);


        AdView mAdView = (AdView) findViewById(R.id.adView);
        AdRequest adRequest = new AdRequest.Builder().build();
        mAdView.loadAd(adRequest);
        MobileAds.initialize(this, "ca-app-pub-8815429757385123~7800940961");



webview=(WebView)findViewById(R.id.Pslams);
        WebSettings webSettings=webview.getSettings();
        webSettings.setJavaScriptEnabled(true);
        webview.setWebViewClient(new WebViewClient());
        webview.loadUrl("http://www.google.org/");



        if (android.os.Build.VERSION.SDK_INT >= 21) {
            CookieManager.getInstance().setAcceptThirdPartyCookies(webview, true);
        }else {
            CookieManager.getInstance().setAcceptCookie(true);
        }




    }




}

这些是我应该给我的项目的权限

<uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"></uses-permission>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<uses-permission android:name="android.permission.CAMERA"/>
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>