Scroll to the last known position in the MessageView when rotating the screen.

src/com/fsck/k9/activity/MessageView.java

@@ -38,6 +38,7 @@ public class MessageView extends K9Activity implements OnClickListener {
     private static final String EXTRA_MESSAGE_REFERENCES = "com.fsck.k9.MessageView_messageReferences";
     private static final String EXTRA_ORIGINATING_INTENT = "com.fsck.k9.MessageView_originatingIntent";
     private static final String EXTRA_NEXT = "com.fsck.k9.MessageView_next";
+    private static final String EXTRA_SCROLL_PERCENTAGE = "com.fsck.k9.MessageView_scrollPercentage";
     private static final String SHOW_PICTURES = "showPictures";
     private static final String STATE_PGP_DATA = "pgpData";
     private static final int ACTIVITY_CHOOSE_FOLDER_MOVE = 1;
@@ -96,6 +97,7 @@ public class MessageView extends K9Activity implements OnClickListener {
     private Listener mListener = new Listener();
     private MessageViewHandler mHandler = new MessageViewHandler();
     private StorageManager.StorageListener mStorageListener = new StorageListenerImplementation();
+    private MessagingListener mLoadCompleteListener = new ScrollToLastLocationListener();
 
     /** this variable is used to save the calling AttachmentView
      *  until the onActivityResult is called.
@@ -109,6 +111,11 @@ public class MessageView extends K9Activity implements OnClickListener {
      */
     private String mDstFolder;
 
+    /**
+     * Used after restore/rotation to scroll our message to the last known location.
+     */
+    private double mScrollPercentage;
+
     private final class StorageListenerImplementation implements StorageManager.StorageListener {
         @Override
         public void onUnmount(String providerId) {
@@ -408,8 +415,14 @@ public class MessageView extends K9Activity implements OnClickListener {
                 }
             };
         });
+
         mMessageView.initialize(this);
 
+        // Add listener for message load completion.  We'll use this to scroll the page to user's last known
+        // location.
+        mController.addListener(mLoadCompleteListener);
+        mMessageView.setListeners(mController.getListeners());
+
         setTitle("");
         final Intent intent = getIntent();
 
@@ -530,6 +543,9 @@ public class MessageView extends K9Activity implements OnClickListener {
         outState.putParcelableArrayList(EXTRA_MESSAGE_REFERENCES, mMessageReferences);
         outState.putSerializable(STATE_PGP_DATA, mPgpData);
         outState.putBoolean(SHOW_PICTURES, mMessageView.showPictures());
+        if(mTopView != null) {
+            outState.putDouble(EXTRA_SCROLL_PERCENTAGE, mTopView.getScrollPercentage());
+        }
     }
 
     @Override
@@ -538,6 +554,7 @@ public class MessageView extends K9Activity implements OnClickListener {
         mPgpData = (PgpData) savedInstanceState.getSerializable(STATE_PGP_DATA);
         mMessageView.updateCryptoLayout(mAccount.getCryptoProvider(), mPgpData, mMessage);
         mMessageView.setLoadPictures(savedInstanceState.getBoolean(SHOW_PICTURES));
+        mScrollPercentage = savedInstanceState.getDouble(EXTRA_SCROLL_PERCENTAGE);
     }
 
     private void displayMessage(MessageReference ref) {
@@ -657,11 +674,13 @@ public class MessageView extends K9Activity implements OnClickListener {
             onAccountUnavailable();
             return;
         }
+        mController.addListener(mLoadCompleteListener);
         StorageManager.getInstance(getApplication()).addListener(mStorageListener);
     }
 
     @Override
     protected void onPause() {
+        mController.removeListener(mLoadCompleteListener);
         StorageManager.getInstance(getApplication()).removeListener(mStorageListener);
         super.onPause();
     }
@@ -873,6 +892,8 @@ public class MessageView extends K9Activity implements OnClickListener {
 
     @Override
     protected void onNext() {
+        // Reset scroll percentage when we change messages
+        mScrollPercentage = 0;
         if (mNextMessage == null) {
             Toast.makeText(this, getString(R.string.end_of_folder), Toast.LENGTH_SHORT).show();
             return;
@@ -888,6 +909,8 @@ public class MessageView extends K9Activity implements OnClickListener {
 
     @Override
     protected void onPrevious() {
+        // Reset scroll percentage when we change messages
+        mScrollPercentage = 0;
         if (mPreviousMessage == null) {
             Toast.makeText(this, getString(R.string.end_of_folder), Toast.LENGTH_SHORT).show();
             return;
@@ -1277,4 +1300,17 @@ public class MessageView extends K9Activity implements OnClickListener {
         mMessageView.loadBodyFromText(mAccount.getCryptoProvider(), mPgpData, mMessage, mPgpData.getDecryptedData(), "text/plain");
     }
 
+    /**
+     * This is a {@link MessagingListener} which listens for when the a message has finished being displayed on the
+     * screen.  We'll scroll the message to the user's last known location once it's done.
+     */
+    class ScrollToLastLocationListener extends MessagingListener {
+        public void messageViewFinished() {
+            // Don't scroll if our last position was at the top.
+            if(mTopView != null && mScrollPercentage != 0.0) {
+                Log.d(K9.LOG_TAG, "MessageView has finished loading, scrolling to last known location.");
+                mTopView.setScrollPercentage(mScrollPercentage);
+            }
+        }
+    }
 }

src/com/fsck/k9/controller/MessagingListener.java

@@ -112,6 +112,11 @@ public class MessagingListener {
     public void loadMessageForViewFailed(Account account, String folder, String uid, Throwable t) {
     }
 
+    /**
+     * Called when a message for view has been fully displayed on the screen.
+     */
+    public void messageViewFinished() {}
+
     public void checkMailStarted(Context context, Account account) {
     }
 

src/com/fsck/k9/view/AccessibleWebView.java

@@ -26,11 +26,15 @@ import android.webkit.WebView;
 import android.widget.TextView;
 
 import com.fsck.k9.activity.AccessibleEmailContentActivity;
+import com.fsck.k9.controller.MessagingListener;
+
+import java.util.Set;
 
 public class AccessibleWebView extends TextView {
     private Context mContext;
     private String mHtmlSource;
     private WebView mDummyWebView;
+    private Set<MessagingListener> mListeners = null;
 
     public AccessibleWebView(Context context) {
         super(context);
@@ -68,6 +72,13 @@ public class AccessibleWebView extends TextView {
                                     String historyUrl) {
         mHtmlSource = data;
         this.setText(Html.fromHtml(mHtmlSource, null, null));
+
+        // Let everyone know that loading has finished.
+        if (mListeners != null) {
+            for (MessagingListener l : mListeners) {
+                l.messageViewFinished();
+            }
+        }
     }
 
     public boolean zoomIn() {
@@ -92,4 +103,8 @@ public class AccessibleWebView extends TextView {
         i.putExtra("content", mHtmlSource);
         mContext.startActivity(i);
     }
+
+    public void setListeners(final Set<MessagingListener> listeners) {
+        this.mListeners = listeners;
+    }
 }

src/com/fsck/k9/view/MessageWebView.java

@@ -1,6 +1,7 @@
 package com.fsck.k9.view;
 
 import android.content.Context;
+import android.graphics.Picture;
 import android.os.Build;
 import android.util.AttributeSet;
 import android.util.Log;
@@ -10,10 +11,15 @@ import android.webkit.WebView;
 import android.widget.Toast;
 import com.fsck.k9.K9;
 import com.fsck.k9.R;
+import com.fsck.k9.controller.MessagingListener;
 
 import java.lang.reflect.Method;
+import java.util.Set;
 
 public class MessageWebView extends WebView {
+    // Store a reference to the listeners in MessagingController.  We can't fetch it directly since
+    // we don't know the application name.
+    private Set<MessagingListener> mListeners = null;
 
     /**
      * We use WebSettings.getBlockNetworkLoads() to prevent the WebView that displays email
@@ -97,6 +103,18 @@ public class MessageWebView extends WebView {
 
         // Disable network images by default.  This is overridden by preferences.
         blockNetworkData(true);
+
+        // Listen for when the screen has finished drawing.
+        setPictureListener(new PictureListener() {
+            @Override
+            public void onNewPicture(WebView webView, Picture picture) {
+                if (mListeners != null) {
+                    for (MessagingListener l : mListeners) {
+                        l.messageViewFinished();
+                    }
+                }
+            }
+        });
     }
 
     /*
@@ -115,4 +133,8 @@ public class MessageWebView extends WebView {
             Log.e(K9.LOG_TAG, "Exception in emulateShiftHeld()", e);
         }
     }
+
+    public void setListeners(final Set<MessagingListener> listeners) {
+        this.mListeners = listeners;
+    }
 }

src/com/fsck/k9/view/SingleMessageView.java

@@ -29,6 +29,7 @@ import com.fsck.k9.mail.internet.MimeUtility;
 import com.fsck.k9.mail.store.LocalStore;
 
 import java.util.List;
+import java.util.Set;
 
 
 /**
@@ -116,11 +117,10 @@ public class SingleMessageView extends LinearLayout {
         return false;
     }
 
-
-
     public boolean showPictures() {
         return mShowPictures;
     }
+
     public void setShowPictures(Boolean show) {
         mShowPictures = show;
     }
@@ -312,4 +312,21 @@ public class SingleMessageView extends LinearLayout {
         AttachmentView.AttachmentFileDownloadCallback attachmentCallback) {
         this.attachmentCallback = attachmentCallback;
     }
+
+    /**
+     * Save a copy of the {@link com.fsck.k9.controller.MessagingController#getListeners()}.  This method will also
+     * pass along these listeners to the underlying views.
+     * @param listeners Set of listeners.
+     */
+    public void setListeners(final Set<MessagingListener> listeners) {
+        if(!mScreenReaderEnabled) {
+            if(mMessageContentView != null) {
+                mMessageContentView.setListeners(listeners);
+            }
+        } else {
+            if(mAccessibleMessageContentView != null) {
+                mAccessibleMessageContentView.setListeners(listeners);
+            }
+        }
+    }
 }

src/com/fsck/k9/view/ToggleScrollView.java

@@ -2,13 +2,19 @@ package com.fsck.k9.view;
 
 import android.content.Context;
 import android.util.AttributeSet;
+import android.util.Log;
 import android.view.GestureDetector;
 import android.view.MotionEvent;
 import android.widget.ScrollView;
+import com.fsck.k9.K9;
 
+/**
+ * An extension of {@link ScrollView} that allows scrolling to be selectively disabled.
+ */
 public class ToggleScrollView extends ScrollView {
     private GestureDetector mDetector;
     private boolean mScrolling = true;
+    private int currentYPosition;
 
     public ToggleScrollView(Context context, AttributeSet attrs) {
         super(context, attrs);
@@ -59,4 +65,44 @@ public class ToggleScrollView extends ScrollView {
             return false;
         }
     }
+
+    /**
+     * Fetch the current percentage by which this view has been scrolled.
+     * @return Scroll percentage based on the top edge of the screen, from 0 to 100.  This number should never really
+     * be 100, unless the screen is of 0 height...
+     */
+    public double getScrollPercentage() {
+        if(computeVerticalScrollRange() == 0) {
+            return 0;
+        }
+        return (double)currentYPosition / computeVerticalScrollRange();
+    }
+
+    /**
+     * Scroll the screen to a specific percentage of the page.  This is based on the top edge of the page.
+     * @param percentage Percentage of page to scroll to.
+     */
+    public void setScrollPercentage(final double percentage) {
+        final int newY = (int)(percentage * computeVerticalScrollRange());
+        Log.d(K9.LOG_TAG, "ToggleScrollView: requested " + (100 * percentage) + "%, scrolling to " + newY + "/" + computeVerticalScrollRange());
+        scrollTo(0, newY);
+    }
+
+    /**
+     * Override {@link ScrollView#onScrollChanged(int, int, int, int)} to record the current x/y position.  We use this
+     * to save our current position for future scrolling.
+     *
+     * @param x
+     * @param y
+     * @param oldx
+     * @param oldy
+     */
+    @Override
+    protected void onScrollChanged(int x, int y, int oldx, int oldy) {
+        super.onScrollChanged(x, y, oldx, oldy);
+
+        this.currentYPosition = y;
+        // I wish Android has a TRACE log level so I wouldn't have to comment this out.  This one is really noisy.
+        // Log.d(K9.LOG_TAG, "ToggleScrollView: currentYPosition=" + y + " scrollRange=" + computeVerticalScrollRange() + " pct=" + getScrollPercentage());
+    }
 }