Android应用程序中的EULA对话框

这是我的MainActivity.java,我想在其中显示EULA:

package com.application;

import android.annotation.SuppressLint;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.content.Intent;
import android.content.SharedPreferences;
import android.graphics.Bitmap;
import android.net.Uri;
import android.preference.PreferenceManager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.webkit.WebView;
import android.webkit.WebViewClient;
import android.webkit.WebChromeClient;
import android.widget.LinearLayout;
import android.widget.ProgressBar;
import android.widget.Toast;

@SuppressWarnings("deprecation")

public class MainActivity extends AppCompatActivity
{
    final SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this);
    boolean agreed = sharedPreferences.getBoolean("agreed",false);

    if(!agreed)
    {
        new AlertDialog.Builder(this, R.style.AlertDialog)
                .setIcon(R.drawable.ic_assignment_late_black_24dp)
                .setTitle(R.string.eula_title)
                .setMessage(R.string.eula)
                .setPositiveButton(R.string.accept, new DialogInterface.OnClickListener()
                        {
                            @Override
                            public void onClick(DialogInterface dialog, int which)
                            {
                                SharedPreferences.Editor editor = sharedPreferences.edit();
                                editor.putBoolean("agreed", true);
                                editor.apply();
                            }
                        })
                .setNegativeButton(R.string.decline, new DialogInterface.OnClickListener()
                {
                    @Override
                    public void onClick(DialogInterface dialog, int which)
                    {
                        finish();
                    }
                })
                .show();
    }

    private WebView WebView;
    private ProgressBar ProgressBar;
    private LinearLayout LinearLayout;
    private String currentURL;

    @SuppressLint("SetJavaScriptEnabled")


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

        WebView = findViewById(R.id.webView);
        ProgressBar = findViewById(R.id.progressBar);
        LinearLayout = findViewById(R.id.layout);

        ProgressBar.setMax(100);

        WebView.loadUrl("https://www.domain.tld/index.html");
        WebView.getSettings().setJavaScriptEnabled(true);
        WebView.getSettings().setUserAgentString("customUA");
        WebView.setWebViewClient(new WebViewClient()
        {
            @Override
            public void onPageStarted(WebView view, String url, Bitmap favicon)
            {
                LinearLayout.setVisibility(View.VISIBLE);
                super.onPageStarted(view, url, favicon);
            }

            @Override
            public void onPageFinished(WebView view, String url)
            {
                LinearLayout.setVisibility(View.GONE);
                super.onPageFinished(view, url);
                currentURL = url;
            }

            @Override
            public void onReceivedError(WebView webview, int i, String s, String s1)
            {
                WebView.setVisibility(View.GONE);

                Intent intent = new Intent(MainActivity.this, ErrorActivity.class);
                startActivity(intent);
                finish();
            }

            @Override
            public boolean shouldOverrideUrlLoading(WebView view, String url2)
            {
                if (url2.contains("www.domain.tld"))
                {
                    view.loadUrl(url2);
                    return false;
                } else
                {
                    Intent intent = new Intent(Intent.ACTION_VIEW, Uri.parse(url2));
                    startActivity(intent);
                    return true;
                }
            }

        });

        WebView.setWebChromeClient(new WebChromeClient()
        {
            @Override
            public void onProgressChanged(WebView view, int newProgress)
            {
                super.onProgressChanged(view, newProgress);
                ProgressBar.setProgress(newProgress);
            }
        });
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu)
    {
        super.onPrepareOptionsMenu(menu);
        MenuInflater menuInflater = getMenuInflater();
        menuInflater.inflate(R.menu.menu, menu);
        return super.onCreateOptionsMenu(menu);
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item)
    {
        switch (item.getItemId())
        {
            case R.id.backward:
                onBackPressed();
                break;

            case R.id.forward:
                onForwardPressed();
                break;

            case R.id.refresh:
                WebView.reload();
                break;

            case R.id.share:
                Intent shareIntent = new Intent(Intent.ACTION_SEND);
                shareIntent.setType("text/plain");
                shareIntent.putExtra(Intent.EXTRA_TEXT,currentURL);
                startActivity(Intent.createChooser(shareIntent, getResources().getText(R.string.shareWith)));
                break;

            case R.id.update:
                Intent intent = new Intent(MainActivity.this, UpdateActivity.class);
                startActivity(intent);
                finish();
                break;

            case R.id.exit:
                new AlertDialog.Builder(this,R.style.AlertDialog)
                        .setIcon(R.drawable.ic_error_black_24dp)
                        .setTitle(R.string.title)
                        .setMessage(R.string.message)
                        .setPositiveButton(R.string.yes,
                                new DialogInterface.OnClickListener()
                                {
                                    @Override
                                    public void onClick(DialogInterface dialog, int which)
                                    {
                                        finish();
                                    }
                                })
                        .setNegativeButton(R.string.no, null)
                        .show();
                break;
        }
        return super.onOptionsItemSelected(item);
    }

    private void onForwardPressed()
    {
        if (WebView.canGoForward())
        {
            WebView.goForward();
        } else
        {
            Toast.makeText(this, R.string.noFurther, Toast.LENGTH_SHORT).show();
        }
    }

    @Override
    public void onBackPressed ()
    {
        if (WebView.canGoBack())
        {
            WebView.goBack();
        } else
        {
            new AlertDialog.Builder(this,R.style.AlertDialog)
                    .setIcon(R.drawable.ic_error_black_24dp)
                    .setTitle(R.string.title)
                    .setMessage(R.string.message)
                    .setPositiveButton(R.string.yes,
                            new DialogInterface.OnClickListener()
                            {
                                @Override
                                public void onClick(DialogInterface dialog, int which)
                                {
                                    finish();
                                }
                            })
                    .setNegativeButton(R.string.no, null)
                    .show();
        }
    }
}

问题是,Android studio正在标记 if(!agreed) 作为一个意外的象征。我该怎么解决?

另外,这种方法是否正确,以实现我在开头所解释的?