MessageWebView.java

package com.fsck.k9.view;


import android.content.Context;
import android.content.pm.PackageManager;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.util.AttributeSet;
import timber.log.Timber;
import android.view.KeyEvent;
import android.webkit.WebSettings;
import android.webkit.WebSettings.LayoutAlgorithm;
import android.webkit.WebSettings.RenderPriority;
import android.webkit.WebView;
import android.widget.Toast;

import com.fsck.k9.K9;
import com.fsck.k9.K9.Theme;
import com.fsck.k9.R;
import com.fsck.k9.mailstore.AttachmentResolver;


public class MessageWebView extends RigidWebView {

    public MessageWebView(Context context) {
        super(context);
    }

    public MessageWebView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public MessageWebView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
    }

    /**
     * Configure a web view to load or not load network data. A <b>true</b> setting here means that
     * network data will be blocked.
     * @param shouldBlockNetworkData True if network data should be blocked, false to allow network data.
     */
    public void blockNetworkData(final boolean shouldBlockNetworkData) {
        /*
         * Block network loads.
         *
         * Images with content: URIs will not be blocked, nor
         * will network images that are already in the WebView cache.
         *
         */
        getSettings().setBlockNetworkLoads(shouldBlockNetworkData);
    }


    /**
     * Configure a {@link WebView} to display a Message. This method takes into account a user's
     * preferences when configuring the view. This message is used to view a message and to display a message being
     * replied to.
     */
    public void configure() {
        this.setVerticalScrollBarEnabled(true);
        this.setVerticalScrollbarOverlay(true);
        this.setScrollBarStyle(SCROLLBARS_INSIDE_OVERLAY);
        this.setLongClickable(true);

        if (K9.getK9MessageViewTheme() == Theme.DARK) {
            // Black theme should get a black webview background
            // we'll set the background of the messages on load
            this.setBackgroundColor(0xff000000);
        }

        final WebSettings webSettings = this.getSettings();

        webSettings.setCacheMode(WebSettings.LOAD_NO_CACHE);

        /* TODO this might improve rendering smoothness when webview is animated into view
        if (VERSION.SDK_INT >= VERSION_CODES.M) {
            webSettings.setOffscreenPreRaster(true);
        }
        */

        webSettings.setSupportZoom(true);
        webSettings.setBuiltInZoomControls(true);
        webSettings.setUseWideViewPort(true);
        if (K9.autofitWidth()) {
            webSettings.setLoadWithOverviewMode(true);
        }

        disableDisplayZoomControls();

        webSettings.setJavaScriptEnabled(false);
        webSettings.setLoadsImagesAutomatically(true);
        webSettings.setRenderPriority(RenderPriority.HIGH);

        // TODO:  Review alternatives.  NARROW_COLUMNS is deprecated on KITKAT
        webSettings.setLayoutAlgorithm(LayoutAlgorithm.NARROW_COLUMNS);

        setOverScrollMode(OVER_SCROLL_NEVER);

        webSettings.setTextZoom(K9.getFontSizes().getMessageViewContentAsPercent());

        // Disable network images by default.  This is overridden by preferences.
        blockNetworkData(true);
    }

    /**
     * Disable on-screen zoom controls on devices that support zooming via pinch-to-zoom.
     */
    private void disableDisplayZoomControls() {
        PackageManager pm = getContext().getPackageManager();
        boolean supportsMultiTouch =
                pm.hasSystemFeature(PackageManager.FEATURE_TOUCHSCREEN_MULTITOUCH) ||
                pm.hasSystemFeature(PackageManager.FEATURE_FAKETOUCH_MULTITOUCH_DISTINCT);

        getSettings().setDisplayZoomControls(!supportsMultiTouch);
    }

    public void displayHtmlContentWithInlineAttachments(@NonNull String htmlText,
            @Nullable AttachmentResolver attachmentResolver, @Nullable OnPageFinishedListener onPageFinishedListener) {
        setWebViewClient(attachmentResolver, onPageFinishedListener);
        setHtmlContent(htmlText);
    }

    private void setWebViewClient(@Nullable AttachmentResolver attachmentResolver,
            @Nullable OnPageFinishedListener onPageFinishedListener) {
        K9WebViewClient webViewClient = K9WebViewClient.newInstance(attachmentResolver);
        if (onPageFinishedListener != null) {
            webViewClient.setOnPageFinishedListener(onPageFinishedListener);
        }
        setWebViewClient(webViewClient);
    }

    private void setHtmlContent(@NonNull String htmlText) {
        loadDataWithBaseURL("about:blank", htmlText, "text/html", "utf-8", null);
        resumeTimers();
    }

    /*
     * Emulate the shift key being pressed to trigger the text selection mode
     * of a WebView.
     */
    public void emulateShiftHeld() {
        try {

            KeyEvent shiftPressEvent = new KeyEvent(0, 0, KeyEvent.ACTION_DOWN,
                                                    KeyEvent.KEYCODE_SHIFT_LEFT, 0, 0);
            shiftPressEvent.dispatch(this, null, null);
            Toast.makeText(getContext() , R.string.select_text_now, Toast.LENGTH_SHORT).show();
        } catch (Exception e) {
            Timber.e(e, "Exception in emulateShiftHeld()");
        }
    }

    public interface OnPageFinishedListener {
        void onPageFinished();
    }
}