按back导航键时Android Webview应用程序强制关闭

import android.webkit.WebView;
import android.webkit.WebViewClient;
import android.app.Activity;
import android.os.Bundle;
import android.view.KeyEvent;

public class MainActivity extends Activity {
    private WebView webView;

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

        webView = findViewById(R.id.webview);
        webView.setWebViewClient(new WebViewClient());
        webView.loadUrl("https://www.example.com");
    }

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