带有后退按钮打开对话框的 Web 视图

Question

我正在创建一个在 Web 视图中打开 url 的应用程序。然后，当按下后退按钮时，这将打开一个对话框，询问用户是否确定是否要退出。虽然对话框工作正常，但应用程序不会加载网站，现在我有错误，所以我在放入 HelloWebViewClient 时甚至无法编译。你有什么建议吗？谢谢！

这是我的代码：

package de.vogella.android.alertdialog;


import android.app.Activity;
import android.app.AlertDialog;
import android.app.AlertDialog.Builder;
import android.app.Dialog;
import android.content.DialogInterface;
import android.os.Bundle;
import android.view.KeyEvent;
import android.view.View;
import android.widget.Toast;
import android.webkit.WebView;
import android.webkit.WebViewClient;
public class ShowMyDialog extends Activity {
    private WebView webview;
    /** Called when the activity is first created. */
    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        if ((keyCode == KeyEvent.KEYCODE_BACK)) {
            openMyDialog(null);
            return true;
        }
        return super.onKeyDown(keyCode, event);
    }


    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        webview = (WebView) findViewById(R.id.webview);
        webview.setWebViewClient(new HelloWebViewClient());
        webview.getSettings().setJavaScriptEnabled(true);
        webview.setInitialScale(50); 
        webview.getSettings().setUseWideViewPort(true); 
        webview.loadUrl("http://mdsitest2.com/");
    }
    private class HelloWebViewClient extends WebViewClient {
        public boolean shouldOverrideUrlLoading(WebView view, String url) {
            view.loadUrl(url);
            return true;

            }



    public void openMyDialog(View view) {
        showDialog(10);
    }
    @Override
    protected Dialog onCreateDialog(int id) {
        switch (id) {
        case 10:
            // Create our AlertDialog
            Builder builder = new AlertDialog.Builder(this);
            builder.setMessage("Are you sure you want to exit?")
                    .setCancelable(true)
                    .setPositiveButton("Yes",
                            new DialogInterface.OnClickListener() {
                                @Override
                                public void onClick(DialogInterface dialog,
                                        int which) {
                                    // Ends the activity
                                    ShowMyDialog.this.finish();
                                }
                            })
                    .setNegativeButton("Keep Guessing!",
                            new DialogInterface.OnClickListener() {
                                @Override
                                public void onClick(DialogInterface dialog,
                                        int which) {
                                    Toast.makeText(getApplicationContext(),
                                            "Good Luck!",
                                            Toast.LENGTH_SHORT).show();
                                }
                            });

            AlertDialog dialog = builder.create();
            dialog.show();
        }
        return super.onCreateDialog(id);
    }
}

.XML：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent" android:layout_height="fill_parent">

<WebView  xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/webview"
    android:layout_height="fill_parent" android:layout_width="fill_parent" android:scrollbarAlwaysDrawVerticalTrack="false"/>


</LinearLayout>

Answer 1

尝试覆盖 onBackPressed 按钮，而不是通过 onKeyDown 执行此操作。 还要实现小精灵的评论...