将消息（loadUrl）从GestureDetector传递到Android上的WebView

GestureDetector

Activity

WebView

loadUrl()

onFling

package com.szuhanchang.friar;

import java.io.IOException;
import java.net.URI;
import java.net.URISyntaxException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.os.Bundle;
import android.view.GestureDetector;
import android.view.KeyEvent;
import android.view.MotionEvent;
import android.webkit.WebSettings;
import android.webkit.WebView;
import android.webkit.WebViewClient;
import android.widget.Toast;

public class Friar extends Activity {
    final String BASE_URL = \"file:///android_asset/book/\";
    final String MIME_TYPE = \"text/html\";
    final String ENCODING = \"utf-8\";

    FriarWebView webView;
    List<String> htmlFiles;
    int currentPage = 0;
    int totalPages = 0;

    GestureDetector gestureDetector;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        System.out.println(\"onCreate!\");
        super.onCreate(savedInstanceState);

        htmlFiles = loadBook();
        totalPages = htmlFiles.size();

        webView = new FriarWebView(this);
        setContentView(webView);

        webView.setWebViewClient(new FriarWebViewClient());
        final WebSettings settings = webView.getSettings();
        settings.setJavaScriptEnabled(false);

        webView.loadUrl(BASE_URL + htmlFiles.get(currentPage));
        System.out.println(BASE_URL + htmlFiles.get(currentPage));
    }

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

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        return super.onTouchEvent(event);
    }

    private List<String> loadBook() {
        List<String> htmlFiles = new ArrayList<String>();
        try {
            String[] files = getAssets().list(\"book\");
            for (String file : files) {
                if (file.endsWith(\".html\")) {
                    htmlFiles.add(file);
                }
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
        Collections.sort(htmlFiles, new AlphanumComparator());
        return htmlFiles;
    }

    public WebView getWebView() {
        return webView;
    }

    class FriarWebView extends WebView {
        Context context;
        GestureDetector gd;

        public FriarWebView(Context context) {
            super(context);
            this.context = context;
            FriarGestureDetector fgd = new FriarGestureDetector();
            gd = new GestureDetector(context, fgd);
        }

        @Override
        public boolean onTouchEvent(MotionEvent event) {
            return gd.onTouchEvent(event) || super.onTouchEvent(event);
        }

        class FriarGestureDetector extends GestureDetector.SimpleOnGestureListener {
            private int swipe_Min_Distance = 100;
            private int swipe_Max_Distance = 350;
            private int swipe_Min_Velocity = 100;

            private void show_toast(final String text) {
                Toast t = Toast.makeText(context, text, Toast.LENGTH_SHORT);
                t.show();
                System.out.println(text);
            }

            private void showUrl(int pageNum) {
                assert pageNum >= 0 && pageNum < totalPages;

                String filename = htmlFiles.get(pageNum);
                String url = BASE_URL + filename;
                getWebView().loadUrl(url);
                getWebView().reload();
                show_toast(url + \", \" + currentPage);
            }

            @Override
            public boolean onDown(MotionEvent event) {
                return false;
            }

            @Override
            public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
                final float xDistance = Math.abs(e1.getX() - e2.getX());
                final float yDistance = Math.abs(e1.getY() - e2.getY());

                if (xDistance > this.swipe_Max_Distance || yDistance > this.swipe_Max_Distance) {
                    return false;
                }

                velocityX = Math.abs(velocityX);
                velocityY = Math.abs(velocityY);

                if (velocityX > this.swipe_Min_Velocity && xDistance > this.swipe_Min_Distance) {
                    if (e1.getX() > e2.getX()) { // right to left
                        show_toast(\"Swipe Left\");
                        if (currentPage + 1 > totalPages) {
                            show_toast(\"This is the last page of the book.\");
                        }
                        else {
                            showUrl(++currentPage);
                        }
                    }
                    else {
                        show_toast(\"Swipe Right\");
                        if (currentPage - 1 < 0) {
                            show_toast(\"This is the first page of the book.\");
                        }
                        else {
                            showUrl(--currentPage);
                        }
                    }
                    setContentView(webView);
                    return true;
                }

                return false;
            }
        }
    }

    class FriarWebViewClient extends WebViewClient {
        @Override
        public void onPageStarted(WebView view, String url, Bitmap favicon) {
            try {
                URI uri = new URI(url);
                String[] segments = uri.getPath().split(\"/\");
                String filename = segments[segments.length - 1];
                if (filename.contains(\"-\")) {
                    currentPage = Integer.parseInt(filename.substring(0, filename.indexOf(\"-\")));
                } else {
                    currentPage = Integer.parseInt(filename.substring(0, filename.indexOf(\".\")));
                }
            } catch (URISyntaxException e) {
                e.printStackTrace();
            }
            System.out.println(currentPage + \" \" + url);
        }
    }
}