RowHeaderPresenter.java revision a00bada00bff4a58436a39472ab14ccb7a8f619d 
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 presentation for {@link HeaderItem} using a
25 * {@link RowHeaderView}. If a subclass creates its own view, the 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    private boolean mNullItemVisibilityGone;
33
34    public RowHeaderPresenter() {
35        this(R.layout.lb_row_header);
36    }
37
38    /**
39     * @hide
40     */
41    public RowHeaderPresenter(int layoutResourceId) {
42        mLayoutResourceId = layoutResourceId;
43    }
44
45    /**
46     * Optionally sets the view visibility to {@link View#GONE} when bound to null.
47     */
48    public void setNullItemVisibilityGone(boolean nullItemVisibilityGone) {
49        mNullItemVisibilityGone = nullItemVisibilityGone;
50    }
51
52    /**
53     * Returns true if the view visibility is set to {@link View#GONE} when bound to null.
54     */
55    public boolean isNullItemVisibilityGone() {
56        return mNullItemVisibilityGone;
57    }
58
59    /**
60     * A ViewHolder for the RowHeaderPresenter.
61     */
62    public static class ViewHolder extends Presenter.ViewHolder {
63        float mSelectLevel;
64        int mOriginalTextColor;
65        float mUnselectAlpha;
66
67        public ViewHolder(View view) {
68            super(view);
69        }
70        public final float getSelectLevel() {
71            return mSelectLevel;
72        }
73    }
74
75    @Override
76    public Presenter.ViewHolder onCreateViewHolder(ViewGroup parent) {
77        RowHeaderView headerView = (RowHeaderView) LayoutInflater.from(parent.getContext())
78                .inflate(mLayoutResourceId, parent, false);
79
80        ViewHolder viewHolder = new ViewHolder(headerView);
81        viewHolder.mOriginalTextColor = headerView.getCurrentTextColor();
82        viewHolder.mUnselectAlpha = parent.getResources().getFraction(
83                R.fraction.lb_browse_header_unselect_alpha, 1, 1);
84        return viewHolder;
85    }
86
87    @Override
88    public void onBindViewHolder(Presenter.ViewHolder viewHolder, Object item) {
89        setSelectLevel((ViewHolder) viewHolder, 0);
90        HeaderItem headerItem = item == null ? null : ((Row) item).getHeaderItem();
91        if (headerItem == null) {
92            ((RowHeaderView) viewHolder.view).setText(null);
93            if (mNullItemVisibilityGone) {
94                viewHolder.view.setVisibility(View.GONE);
95            }
96        } else {
97            viewHolder.view.setVisibility(View.VISIBLE);
98            ((RowHeaderView) viewHolder.view).setText(headerItem.getName());
99        }
100    }
101
102    @Override
103    public void onUnbindViewHolder(Presenter.ViewHolder viewHolder) {
104        ((RowHeaderView) viewHolder.view).setText(null);
105    }
106
107    /**
108     * Sets the select level.
109     */
110    public final void setSelectLevel(ViewHolder holder, float selectLevel) {
111        holder.mSelectLevel = selectLevel;
112        onSelectLevelChanged(holder);
113    }
114
115    /**
116     * Called when the select level changes.  The default implementation sets the alpha on the view.
117     */
118    protected void onSelectLevelChanged(ViewHolder holder) {
119        holder.view.setAlpha(holder.mUnselectAlpha + holder.mSelectLevel *
120                (1f - holder.mUnselectAlpha));
121    }
122
123    /**
124     * Returns the space (distance in pixels) below the baseline of the
125     * text view, if one exists; otherwise, returns 0.
126     */
127    public int getSpaceUnderBaseline(ViewHolder holder) {
128        int space = holder.view.getPaddingBottom();
129        if (holder.view instanceof TextView) {
130            space += (int) getFontDescent((TextView) holder.view, mFontMeasurePaint);
131        }
132        return space;
133    }
134
135    protected static float getFontDescent(TextView textView, Paint fontMeasurePaint) {
136        if (fontMeasurePaint.getTextSize() != textView.getTextSize()) {
137            fontMeasurePaint.setTextSize(textView.getTextSize());
138        }
139        if (fontMeasurePaint.getTypeface() != textView.getTypeface()) {
140            fontMeasurePaint.setTypeface(textView.getTypeface());
141        }
142        return fontMeasurePaint.descent();
143    }
144}
145