1/*
2 * Copyright (C) 2014 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
5 * in compliance with the License. You may obtain a copy of the License at
6 *
7 * http://www.apache.org/licenses/LICENSE-2.0
8 *
9 * Unless required by applicable law or agreed to in writing, software distributed under the License
10 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
11 * or implied. See the License for the specific language governing permissions and limitations under
12 * the License.
13 */
14package android.support.v17.leanback.widget;
15
16import android.graphics.Paint;
17import android.support.v17.leanback.R;
18import android.view.LayoutInflater;
19import android.view.View;
20import android.view.ViewGroup;
21import android.widget.TextView;
22
23/**
24 * RowHeaderPresenter provides a default implementation for header using TextView.
25 * If subclass override and creates its own view, subclass must also override
26 * {@link #onSelectLevelChanged(ViewHolder)}.
27 */
28public class RowHeaderPresenter extends Presenter {
29
30    private final int mLayoutResourceId;
31    private final Paint mFontMeasurePaint = new Paint(Paint.ANTI_ALIAS_FLAG);
32
33    public RowHeaderPresenter() {
34        this(R.layout.lb_row_header);
35    }
36
37    /**
38     * @hide
39     */
40    public RowHeaderPresenter(int layoutResourceId) {
41        mLayoutResourceId = layoutResourceId;
42    }
43
44    public static class ViewHolder extends Presenter.ViewHolder {
45        float mSelectLevel;
46        int mOriginalTextColor;
47        float mUnselectAlpha;
48
49        public ViewHolder(View view) {
50            super(view);
51        }
52        public final float getSelectLevel() {
53            return mSelectLevel;
54        }
55    }
56
57    @Override
58    public Presenter.ViewHolder onCreateViewHolder(ViewGroup parent) {
59        RowHeaderView headerView = (RowHeaderView) LayoutInflater.from(parent.getContext())
60                .inflate(mLayoutResourceId, parent, false);
61
62        ViewHolder viewHolder = new ViewHolder(headerView);
63        viewHolder.mOriginalTextColor = headerView.getCurrentTextColor();
64        viewHolder.mUnselectAlpha = parent.getResources().getFraction(
65                R.fraction.lb_browse_header_unselect_alpha, 1, 1);
66        return viewHolder;
67    }
68
69    @Override
70    public void onBindViewHolder(Presenter.ViewHolder viewHolder, Object item) {
71        setSelectLevel((ViewHolder) viewHolder, 0);
72        Row rowItem = (Row) item;
73        if (rowItem != null) {
74            HeaderItem headerItem = rowItem.getHeaderItem();
75            if (headerItem != null) {
76                String text = headerItem.getName();
77                ((RowHeaderView) viewHolder.view).setText(text);
78            }
79        }
80    }
81
82    @Override
83    public void onUnbindViewHolder(Presenter.ViewHolder viewHolder) {
84    }
85
86    public final void setSelectLevel(ViewHolder holder, float selectLevel) {
87        holder.mSelectLevel = selectLevel;
88        onSelectLevelChanged(holder);
89    }
90
91    protected void onSelectLevelChanged(ViewHolder holder) {
92        holder.view.setAlpha(holder.mUnselectAlpha + holder.mSelectLevel *
93                (1f - holder.mUnselectAlpha));
94    }
95
96    /**
97     * Returns the space (distance in pixels) below the baseline of the
98     * text view, if one exists; otherwise, returns 0.
99     */
100    public int getSpaceUnderBaseline(ViewHolder holder) {
101        int space = holder.view.getPaddingBottom();
102        if (holder.view instanceof TextView) {
103            space += (int) getFontDescent((TextView) holder.view, mFontMeasurePaint);
104        }
105        return space;
106    }
107
108    protected static float getFontDescent(TextView textView, Paint fontMeasurePaint) {
109        if (fontMeasurePaint.getTextSize() != textView.getTextSize()) {
110            fontMeasurePaint.setTextSize(textView.getTextSize());
111        }
112        if (fontMeasurePaint.getTypeface() != textView.getTypeface()) {
113            fontMeasurePaint.setTypeface(textView.getTypeface());
114        }
115        return fontMeasurePaint.descent();
116    }
117}
118