RowHeaderPresenter.java revision ad9af35ec6a808136478daf7bd57d564ac517e0e 
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    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    public static class ViewHolder extends Presenter.ViewHolder {
60        float mSelectLevel;
61        int mOriginalTextColor;
62        float mUnselectAlpha;
63
64        public ViewHolder(View view) {
65            super(view);
66        }
67        public final float getSelectLevel() {
68            return mSelectLevel;
69        }
70    }
71
72    @Override
73    public Presenter.ViewHolder onCreateViewHolder(ViewGroup parent) {
74        RowHeaderView headerView = (RowHeaderView) LayoutInflater.from(parent.getContext())
75                .inflate(mLayoutResourceId, parent, false);
76
77        ViewHolder viewHolder = new ViewHolder(headerView);
78        viewHolder.mOriginalTextColor = headerView.getCurrentTextColor();
79        viewHolder.mUnselectAlpha = parent.getResources().getFraction(
80                R.fraction.lb_browse_header_unselect_alpha, 1, 1);
81        return viewHolder;
82    }
83
84    @Override
85    public void onBindViewHolder(Presenter.ViewHolder viewHolder, Object item) {
86        setSelectLevel((ViewHolder) viewHolder, 0);
87        HeaderItem headerItem = item == null ? null : ((Row) item).getHeaderItem();
88        if (headerItem == null) {
89            ((RowHeaderView) viewHolder.view).setText(null);
90            if (mNullItemVisibilityGone) {
91                viewHolder.view.setVisibility(View.GONE);
92            }
93        } else {
94            viewHolder.view.setVisibility(View.VISIBLE);
95            ((RowHeaderView) viewHolder.view).setText(headerItem.getName());
96        }
97    }
98
99    @Override
100    public void onUnbindViewHolder(Presenter.ViewHolder viewHolder) {
101        ((RowHeaderView) viewHolder.view).setText(null);
102    }
103
104    public final void setSelectLevel(ViewHolder holder, float selectLevel) {
105        holder.mSelectLevel = selectLevel;
106        onSelectLevelChanged(holder);
107    }
108
109    protected void onSelectLevelChanged(ViewHolder holder) {
110        holder.view.setAlpha(holder.mUnselectAlpha + holder.mSelectLevel *
111                (1f - holder.mUnselectAlpha));
112    }
113
114    /**
115     * Returns the space (distance in pixels) below the baseline of the
116     * text view, if one exists; otherwise, returns 0.
117     */
118    public int getSpaceUnderBaseline(ViewHolder holder) {
119        int space = holder.view.getPaddingBottom();
120        if (holder.view instanceof TextView) {
121            space += (int) getFontDescent((TextView) holder.view, mFontMeasurePaint);
122        }
123        return space;
124    }
125
126    protected static float getFontDescent(TextView textView, Paint fontMeasurePaint) {
127        if (fontMeasurePaint.getTextSize() != textView.getTextSize()) {
128            fontMeasurePaint.setTextSize(textView.getTextSize());
129        }
130        if (fontMeasurePaint.getTypeface() != textView.getTypeface()) {
131            fontMeasurePaint.setTypeface(textView.getTypeface());
132        }
133        return fontMeasurePaint.descent();
134    }
135}
136