为什么我不能在 android 的 webview 中注入这个 javascript？

Question

在我的应用程序中，我正在加载一个 webview。 我在这个 webview 中加载的网站有一个菜单按钮，但我不想显示它。 所以我写了下面的代码。 但是，这不起作用，我不知道为什么......

{
    @Override
    public void onPageFinished(WebView view, String url)
    {
        // when a page has finished loading dismiss any progress dialog
        if (progressDialog != null && progressDialog.isShowing())
        {
            progressDialog.dismiss();
            String javascript="javascript: document.getElementById('menu-toggle').css('display','none');";
            myWebView.loadUrl(javascript);
        }
    }
});

更新：这是仍然无法正常工作的完整 java 文件，我似乎无法找到问题所在：

package test.firstapp;

import android.app.Activity;
import android.app.ProgressDialog;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBar;
import android.support.v7.app.ActionBarActivity;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.webkit.WebChromeClient;
import android.webkit.WebView;
import android.webkit.WebViewClient;


public class login
    extends ActionBarActivity
    implements NavigationDrawerFragment.NavigationDrawerCallbacks
{

/**
 * Fragment managing the behaviors, interactions and presentation of the
 * navigation drawer.
 */
private NavigationDrawerFragment mNavigationDrawerFragment;

/**
 * Used to store the last screen title. For use in
 * {@link #restoreActionBar()}.
 */
private CharSequence mTitle;

// we need a class level references to some objects to be able to modify the
//   target address outside of onCreate()
private WebView myWebView;
private ActionBar actionBar;
private ProgressDialog progressDialog;

// keep the pair of String arrays of site names and addresses
private String[] siteNames;
private String[] siteAddresses;

private static final String TAG = "MainActivity";

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

    // grab the needed website arrays
    siteNames = getResources().getStringArray(R.array.site_names);
    siteAddresses = getResources().getStringArray(R.array.site_addresses);

    // set up WebView. initial page load comes from NavDrawerFragment attach
    myWebView = (WebView) findViewById(R.id.main_webview);
    myWebView.getSettings().setJavaScriptEnabled(true);
    myWebView.setWebChromeClient(new WebChromeClient());
    myWebView.setWebViewClient(new WebViewClient()
    {

        @Override
        public void onPageFinished(WebView view, String url)
        {
            // when a page has finished loading dismiss any progress dialog
            if (progressDialog != null && progressDialog.isShowing())
            {
                progressDialog.dismiss();
            }
            String javascript="javascript:"+
                                        "document.getElementById('menu-toggle').css('display','none');";
            myWebView.evaluateJavascript(javascript, null);
        }
    });

    // Set up the drawer.
    mNavigationDrawerFragment = (NavigationDrawerFragment) getSupportFragmentManager()
            .findFragmentById(R.id.navigation_drawer);
    mNavigationDrawerFragment.setUp(R.id.navigation_drawer,
            (DrawerLayout) findViewById(R.id.drawer_layout));
}

@Override
public void onNavigationDrawerItemSelected(int siteIndex)
{
    // user selected page load
    Log.d(TAG, "(onNavSelect) received index: " + siteIndex);
    loadWebPage(siteIndex);
}

public void onSectionAttached(int siteIndex)
{
    // initial page load. not user selected.
    loadWebPage(siteIndex);
}

public void restoreActionBar()
{
    actionBar = getSupportActionBar();
    actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_STANDARD);
    actionBar.setDisplayShowTitleEnabled(true);
    actionBar.setTitle(mTitle);
}

private void loadWebPage(int siteIndex)
{
    // lets show a progress indicator instead of a blank screen
    if (progressDialog == null)
    {
        initProgressDialog();
    }
    progressDialog.show();

    // load the page
    Log.d(TAG, "(loadWebPage) Loading page: " + siteNames[siteIndex] + "("
            + siteAddresses[siteIndex] + ")");
    mTitle = siteNames[siteIndex];
    if (actionBar == null)
    {
        restoreActionBar();
    }
    else
    {
        actionBar.setTitle(mTitle);
    }
    myWebView.getSettings().setJavaScriptEnabled(true);
    myWebView.loadUrl(siteAddresses[siteIndex]);
    myWebView.loadUrl(siteAddresses[siteIndex]);

    // progressDialog gets dismissed above in WebViewclient declaration
}

private void initProgressDialog()
{
    progressDialog = new ProgressDialog(this, ProgressDialog.STYLE_SPINNER);
    progressDialog.setIndeterminate(true);
    progressDialog.setMessage(getString(R.string.page_load_progress_message));
}


@Override
public boolean onCreateOptionsMenu(Menu menu)
{
    if (!mNavigationDrawerFragment.isDrawerOpen())
    {
        // Only show items in the action bar relevant to this screen
        // if the drawer is not showing. Otherwise, let the drawer
        // decide what to show in the action bar.
        getMenuInflater().inflate(R.menu.global, menu);
        restoreActionBar();
        return true;
    }
    return super.onCreateOptionsMenu(menu);
}

@Override
public boolean onOptionsItemSelected(MenuItem item)
{
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    if (actionBar == null)
    {
        restoreActionBar();
    }
    else
    {

    }
    int id = item.getItemId();
    if (id == R.id.action_settings)
    {
        myWebView.loadUrl("settings");
        myWebView.loadUrl("settings");
        actionBar.setTitle("Settings");
        return true;
    }
    return super.onOptionsItemSelected(item);
}

/**
 * A placeholder fragment containing a simple view.
 */
public static class PlaceholderFragment
        extends Fragment
{

    /**
     * The fragment argument representing the section number for this
     * fragment.
     */
    private static final String ARG_SELECTED_SITE_INDEX = "selected_site_index";

    /**
     * Returns a new instance of this fragment for the given section
     * number.
     */
    public static PlaceholderFragment newInstance(int siteIndex)
    {
        PlaceholderFragment fragment = new PlaceholderFragment();
        Bundle args = new Bundle();
        args.putInt(ARG_SELECTED_SITE_INDEX, siteIndex);
        fragment.setArguments(args);
        return fragment;
    }

    public PlaceholderFragment()
    {}

    @Override
    public View onCreateView(LayoutInflater inflater,
                             ViewGroup container,
                             Bundle savedInstanceState)
    {
        View rootView = inflater.inflate(R.layout.fragment_login, container, false);
        return rootView;
    }

    @Override
    public void onAttach(Activity activity)
    {
        super.onAttach(activity);
        // Here is where you can define the default page you want loaded
        //  or if you want to save/restore the last page viewed etc.
        ((login) activity)
                .onSectionAttached(getArguments().getInt(ARG_SELECTED_SITE_INDEX));
    }
}

}

Answer 1

在 Android 4.4+ 上，您需要使用evaluateJavascript()而不是loadUrl("javascript:...")作为在WebView中执行 JavaScript 的方式。

Answer 2

您调用的方法称为loadURL ，它不是 JavaScript。 要使其正确加载，请将 JS 包裹在一个虚拟页面中，如下所示：

<html>
    <head>
        <script type="text/javascript">YourJavascripthere</script>
    </head>
    <body />
</html>

并调用webView.loadData(textData, "text/html", null); .

有关更多信息，请参阅： http : //developer.android.com/reference/android/webkit/WebView.html

Answer 3

使用以下代码加载 javascript。

String javascript="javascript: document.getElementById('menu-toggle').css('display','none');";
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
     myWebView.evaluateJavascript(javascript, null);
}else{
    myWebView.loadUrl(javascript);
}