java - 如何从菜单外部访问选项菜单项

Question

如何从菜单本身之外的对象访问选项菜单项？我正在尝试为选项菜单项之一设置 alpha 值，但由于某种原因它不起作用。注释行是我尝试过的。

我以前看过以下代码，但不清楚应该在哪里以及如何使用它：

    Drawable drawable = item.getIcon();
    if (drawable != null) {
        drawable.mutate();
        drawable.setAlpha(1);
    }

活动课

public class WebviewActivity extends AppCompatActivity {
    private static final String TAG = WebviewActivity.class.getSimpleName();

    WebView myWebView;
    ProgressBar myProgressBar;

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

    @Override
    protected void onStart() {
        super.onStart();
        setContentView(R.layout.fragment_webview);

        String url = getIntent().getStringExtra("url");
        myWebView = findViewById(R.id.web_view);
        myWebView.setWebViewClient(new WebViewClient());
        WebSettings webSettings = myWebView.getSettings();
        webSettings.setJavaScriptEnabled(true);
        myWebView.loadUrl(url);

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

    private class WebViewClient extends android.webkit.WebViewClient {
        @Override
        public boolean shouldOverrideUrlLoading(WebView view, WebResourceRequest request){
            String url=request.getUrl().toString();
            view.loadUrl(url);
            return true;
        }

        @Override
        public void onPageFinished(WebView view, String url) {
            super.onPageFinished(view, url);
        }
    }

    public void onBtnBackPressed() {
        if (myWebView.canGoBack()){
            myWebView.goBack();
        } else {
            onBackPressed();
        }
    }

    public void onBtnForwardPressed() {
        if (myWebView.canGoForward()){
            myWebView.goForward();
        } else {
//            menu.getItem(R.id.action_webbrowser_forward).setEnabled(false);
//            menu.getItem(R.id.action_webbrowser_forward).mutate();
//            menu.getItem(R.id.action_webbrowser_forward).setAlpha(1);
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        MenuInflater inflater = getMenuInflater();
        inflater.inflate(R.menu.web_browser, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        else if (item.getItemId() == R.id.action_webbrowser_back) {
            onBtnBackPressed();
        } else if (item.getItemId() == R.id.action_webbrowser_forward) {
            onBtnForwardPressed();
        }
        return super.onOptionsItemSelected(item);
    }
}

标签： javaandroidandroid-webviewandroid-optionsmenu

Answer 1

尝试在您的函数参数上传递MenuItem引用：onBtnForwardPressed

@Override
    public boolean onOptionsItemSelected(MenuItem item) {
        else if (item.getItemId() == R.id.action_webbrowser_back) {
            onBtnBackPressed();
        } else if (item.getItemId() == R.id.action_webbrowser_forward) {
            onBtnForwardPressed(item);
        }
        return super.onOptionsItemSelected(item);
    }

和 ：

public void onBtnForwardPressed(MenuItem menuItem) {
        if (myWebView.canGoForward()){
            myWebView.goForward();
        } else {
            menuItem.setEnabled(false);
            menuItem.getIcon().setAlpha(50);

        }
    }

希望这可以帮助