onBackPressed() - 无法解析符号“webView”

Question

我试图在我的 WebView 应用程序中恢复按钮功能，但 onBackPressed() 函数给出错误“无法解析符号 webView”

这是我的代码：

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

    AdView mAdView;
    mAdView = (AdView) findViewById(R.id.adView);
    AdRequest adRequest = new AdRequest.Builder().build();
    mAdView.loadAd(adRequest);

    WebView webView = (WebView) findViewById(R.id.webview);

    WebSettings webSettings = webView.getSettings();
    webSettings.setJavaScriptEnabled(true);

    // To keep browser in width of phone
    webView.getSettings().setUseWideViewPort(true);
    webView.getSettings().setLoadWithOverviewMode(true);

    // Sets default text size
    webSettings.setTextZoom(175);

    MyWebViewClient webViewClient = new MyWebViewClient();
    webView.setWebViewClient(webViewClient);

    webView.loadUrl("http://www.google.com");
}

@Override
public void onBackPressed() {
    if (webView.canGoBack()) {
        webView.goBack();
    } else {
        super.onBackPressed();
    }
}

Answer 1

您可以在 onBackPressed 中执行此操作：

    @Override
public void onBackPressed() {
    WebView webView = (WebView) findViewById(R.id.webview);
    if (webView.canGoBack()) {
        webView.goBack();
    } else {
        super.onBackPressed();
    }
}

编辑： 您可以这样做（使用字段）：

private WebView webView;
@Override
protected void onCreate(Bundle savedInstanceState){
      // ...
      this.webView = (WebView) findViewById(R.id.webView);
      // ...
}

@Override
public void onBackPressed(){
    // now you don't need findViewById because you can access field prepared in onCreate
    if (webView.canGoBack()) {
        webView.goBack();
    } else {
        super.onBackPressed();
    }
}