How to attach multiple touch actions to a single l

问题:

I am using the following list layout for items that have associated comments. The number of comments are indicated by the box on the right side.

Currently, I am using the onListItemClick handler to launch another details view.

public class CustomListFragment extends ListFragment
                                implements LoaderCallbacks<Cursor> {

    private Activity mActivity;
    private CursorAdapter mAdapter;
    private QueryParameters mQueryParameters;

    @Override
    public void onActivityCreated(Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        setEmptyText("No data to display");

        mActivity = getActivity();
        if (mActivity == null)  {
            Log.e(getClass().getName(), "Activity is null");
            return;
        }
        // Prepare query.
        mQueryParameters = QueryHelper.getQueryParameters(mActivity);
        if (mQueryParameters == null || !mQueryParameters.isPreparedForLoader()) {
            Log.d(getClass().getName(), "One or more query parameters are null.");
            return;
        }
        mAdapter = new CustomCursorAdapter(mActivity, null, 0);
        setListAdapter(mAdapter);
        getLoaderManager().initLoader(0, null, this);
    }

    @Override
    public Loader<Cursor> onCreateLoader(int id, Bundle extras) {
        return new CursorLoader(mActivity,
                mQueryParameters.uri,
                mQueryParameters.fromColumnsLoader,
                mQueryParameters.selection,
                mQueryParameters.selectionArgs,
                mQueryParameters.sortOrder);
    }

    @Override
    public void onLoadFinished(Loader<Cursor> loader, Cursor cursor) {
        mAdapter.swapCursor(cursor);
    }

    @Override
    public void onLoaderReset(Loader<Cursor> loader) {
        mAdapter.swapCursor(null);
    }

    @Override
    public void onListItemClick(ListView l, View v, int position, long id) {
        Intent intent = new Intent(mActivity, ItemDetailsActivity.class);
        intent.putExtra("ITEM_URI", mItemUri);
        mActivity.startActivity(intent);
    }
}

I would like to implement that the user can touch the box element on the right. This action should then start the associated CommentsActivity. When the user touches the left side, however, it should still launch the ItemDetailsActivity.
In both cases, I need to pass the itemUri with the intent so that either the details view or the comments list for the particular item can be loaded.
The ListFragment uses a CursorAdapter to bind the TextViews to the properties of an item.

Question:

• How can I attach a second touch action to a single list item?

回答1:

You hadn't posted any code relating to the adapter itself, but I found your previous question and you are most of the way there.

The Quick and Dirty Answer

In bindView(), let's modify your comments_count TextView to save the index of the current row in the tag (for your itemUri) and add a simple OnClickListener:

public void bindView(View view, Context context, Cursor cursor) {
    ViewHolder holder = (ViewHolder)view.getTag();
    if (holder == null) {
        ...
        holder.comments_count.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                // Get the position from the ViewHolder
                long id = (Long) v.getTag();
                Toast.makeText(v.getContext(), "Comment Click: " + id, Toast.LENGTH_SHORT).show();
            }
        });
    }
    ...
    holder.comments_count.setTag(cursor.getLong(0));
}

When the user clicks on the row it will still call onListItemClick(), except if they click on the comments box. The comments box fires the OnClickListener above where you can direct the user to your CommentsActivity. You didn't mention where you fetch the different values for itemUri but I assumed you need the row's id to get it.

---

Superior Answer

In your previous question, I noticed that you are making some repetitive calls and that Thiago Moreira Rocha's layout was extremely complex to be used repeatedly (for every ListView row.) So I propose a different approach. I've divided my answer into parts relating to the adapter, row layout, and colors for comments_count:

The Adapter
I'll post the code in full and then explain at the bottom:

public class CustomCursorAdapter extends CursorAdapter {
    private LayoutInflater mInflater;
    private int[] mFrom;

    private OnClickListener commentClick = new OnClickListener() {
        @Override
        public void onClick(View v) {
            // Get the position saved in bindView()
            long id = (Long) v.getTag();
            Toast.makeText(v.getContext(), "Comment Click: " + id, Toast.LENGTH_SHORT).show();
        }
    };

    public CustomCursorAdapter(Context context, Cursor cursor, int flags) {
        super(context, cursor, flags);
        mInflater = LayoutInflater.from(context);
    }

    private void applyColorFilter(Drawable drawable, int count) {
        drawable.clearColorFilter();
        if (count > 0) {
            float saturation = (count * 15) / 100f;
            // The value gets pinned if out of range.
            int color = Color.HSVToColor(new float[] {110f, saturation, 1f});
            drawable.setColorFilter(color, Mode.SRC);
        }
    }

    @Override
    public void bindView(View view, Context context, Cursor cursor) {
        ViewHolder holder = (ViewHolder) view.getTag();
        holder.title.setText(cursor.getString(mFrom[0]));
        holder.description.setText(cursor.getString(mFrom[1]));

        // Get comments_count and set it as text
        int count = cursor.getInt(mFrom[2]);
        holder.comments_count.setText(count + "");
        holder.comments_count.setTag(cursor.getLong(0));

        // Adjust the color by saturation
        applyColorFilter(holder.comments_color, count);

        // Alternate method, that I explain in the answer
        //   Note: set the solid color in color.xml to #2aff00 
        //holder.comments_color.setAlpha(count * 45);
    }

    @Override
    public View newView(Context context, Cursor cursor, ViewGroup parent) {
        View view = mInflater.inflate(R.layout.list_item, parent, false);

        ViewHolder holder = new ViewHolder();
        holder.title = (TextView)view.findViewById(R.id.title);
        holder.description = (TextView)view.findViewById(R.id.description);
        holder.comments_count = (TextView)view.findViewById(R.id.comments_count);
        holder.comments_count.setOnClickListener(commentClick);
        holder.comments_color = ((LayerDrawable) holder.comments_count.getBackground()).findDrawableByLayerId(R.id.color);

        view.setTag(holder);

        return view;
    }

    @Override
    public Cursor swapCursor(Cursor newCursor) {
        if(mFrom == null && newCursor != null) {
            mFrom = new int[] {newCursor.getColumnIndex(TITLE), newCursor.getColumnIndex(DESCRIPTION), newCursor.getColumnIndex(COMMENTS_COUNT)};
        }
        return super.swapCursor(newCursor);
    }

    private class ViewHolder {
        TextView title;
        TextView description;
        TextView comments_count;
        Drawable comments_color;
    }
}

I made a few changes:

• mFrom holds the indices of the columns that you are using. You only need to get the column index once, it won't change unless you change the Cursor
• commentsClick is one generic OnClickListener that I use for every row and I set it while creating a ViewHolder
• I brought your method for changing the HSV color into the adapter and called it applyColorFilter()
• I moved creating the ViewHolder into newView() rather than checking for a null one in bindView()

---

The Row Layout
You probably noticed that I change the comments' color a little differently, that is because I use a simpler row layout:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:padding="10dp" >

    <TextView
        android:id="@+id/title"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_toLeftOf="@+id/comments_count"
        android:textAppearance="?android:attr/textAppearanceLarge" />

    <TextView
        android:id="@+id/description"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_below="@+id/title"
        android:layout_toLeftOf="@+id/comments_count"
        android:textAppearance="?android:attr/textAppearanceSmall" />

    <TextView
        android:id="@+id/comments_count"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentRight="true"
        android:layout_centerVertical="true"
        android:layout_marginRight="15dp"
        android:background="@drawable/comments_layers"
        android:textAppearance="?android:attr/textAppearanceLarge" />

</RelativeLayout>

(While Thiago Moreira Rocha's layout works, the nested ViewGroups seem like overkill. Anytime you have a ViewGroup with only one child, their is usually an alternative.)

I use a LayerDrawable to replace the two LinearLayouts, that I will explain in in steps. First, the border (border.xml), very similar to the previous one:

<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle" >
    <corners android:radius="10dp" />
    <padding android:bottom="2dp" android:left="2dp" android:right="2dp" android:top="2dp" />
    <solid android:color="#ffffff" />
    <stroke android:width="2dp"
        android:color="#000000" />
</shape>

(Notice the padding is the width of the stroke.)

Second, the adjustable background color (color.xml):

<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle" >
    <corners android:radius="10dp" />
    <padding android:bottom="10dp" android:left="10dp" android:right="10dp" android:top="10dp" />
    <solid android:color="#ffffff" />
</shape>

Last, I created a LayerDrawable to combine the two images (comments_layers.xml):

<layer-list xmlns:android="http://schemas.android.com/apk/res/android" >
    <item 
        android:id="@+id/border"
        android:drawable="@drawable/border" />
    <item 
        android:id="@+id/color"
        android:drawable="@drawable/color" />
</layer-list>

---

(Optional)
You adjust the saturation of your HSV value in applyColorFilter(), but it seems that this is the equivalent to adjusting the alpha of a green background. If this is true, the changing the alpha value is a much simpler task. Find my comments in bindView():

1. Comment out applyColorFilter(holder.comments_color, count);
2. Uncomment holder.comments_color.setAlpha(count * 45);
3. Open my color.xml file and change the color attribute of the solid element from #ffffff to #2aff00

---

In all truth I had never used LayerDrawables like this before, there may be a faster way, but I think this is pretty slick.