Java &&显示为意外标记

我在if-else条件下使用&&遇到“意外令牌”错误。没有任何其他错误

keyCode==KeyEvent.KEYCODE_BACK) && webViewsupport.canGoBack

我无法理解为什么它会在这里显示意外的令牌来使用&&

import android.graphics.Bitmap;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v7.app.AppCompatActivity;
import android.view.KeyEvent;
import android.view.View;
import android.webkit.WebView;
import android.webkit.WebViewClient;
import android.widget.ProgressBar; 



public class Support extends AppCompatActivity {
    WebView webViewsupport;
    ProgressBar progressBar;

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

        webViewsupport = (WebView) findViewById(R.id.webView);
        progressBar = (ProgressBar)findViewById(R.id.progressBar2);

        webViewsupport.setWebViewClient(new myWebClient());
        webViewsupport.getSettings().setJavaScriptEnabled(true);
        webViewsupport.loadUrl("https://example.com");

    }
    public class myWebClient extends WebViewClient{
        @Override
        public void onPageFinished(WebView view, String url) {
            super.onPageFinished(view, url);
            progressBar.setVisibility(View.GONE);
        }

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

        @Override
        public boolean shouldOverrideUrlLoading(WebView view, String url) {
            view.loadUrl(url);
            return super.shouldOverrideUrlLoading(view, url);

        }
    }

    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        if(keyCode==KeyEvent.KEYCODE_BACK) && webViewsupport.canGoBack(){
            webViewsupport.goBack();
        }
        return super.onKeyDown(keyCode, event);
    }
}

---

您需要将整个条件添加到：

public boolean onKeyDown(int keyCode, KeyEvent event) {
    if (keyCode==KeyEvent.KEYCODE_BACK && webViewsupport.canGoBack()){
        webViewsupport.goBack();
    }
    return super.onKeyDown(keyCode, event);
}

---

您的代码中有一个输入错误，您的结尾括号放错了位置：

if (keyCode == KeyEvent.KEYCODE_BACK) && webViewsupport.canGoBack(){
    webViewsupport.goBack();
}

应该是：

if (keyCode == KeyEvent.KEYCODE_BACK && webViewsupport.canGoBack()) {
    webViewsupport.goBack();
}

---

因此投票关闭。

将关闭括号移到canGoBack后。