public class

RowHeaderPresenter

extends Presenter

 java.lang.Object

androidx.leanback.widget.Presenter

↳androidx.leanback.widget.RowHeaderPresenter

Gradle dependencies

compile group: 'androidx.leanback', name: 'leanback', version: '1.2.0-alpha02'

  • groupId: androidx.leanback
  • artifactId: leanback
  • version: 1.2.0-alpha02

Artifact androidx.leanback:leanback:1.2.0-alpha02 it located at Google repository (https://maven.google.com/)

Androidx artifact mapping:

androidx.leanback:leanback com.android.support:leanback-v17

Androidx class mapping:

androidx.leanback.widget.RowHeaderPresenter android.support.v17.leanback.widget.RowHeaderPresenter

Overview

RowHeaderPresenter provides a default presentation for HeaderItem using a RowHeaderView and optionally a TextView for description. If a subclass creates its own view, the subclass must also override RowHeaderPresenter.onCreateViewHolder(ViewGroup), RowHeaderPresenter.onSelectLevelChanged(RowHeaderPresenter.ViewHolder).

Summary

Constructors
publicRowHeaderPresenter()

Creates default RowHeaderPresenter using a title view and a description view.

publicRowHeaderPresenter(int layoutResourceId)

publicRowHeaderPresenter(int layoutResourceId, boolean animateSelect)

Methods
protected static floatgetFontDescent(TextView textView, Paint fontMeasurePaint)

public intgetSpaceUnderBaseline(RowHeaderPresenter.ViewHolder holder)

Returns the space (distance in pixels) below the baseline of the text view, if one exists; otherwise, returns 0.

public booleanisNullItemVisibilityGone()

Returns true if the view visibility is set to View when bound to null.

public abstract voidonBindViewHolder(Presenter.ViewHolder viewHolder, java.lang.Object item)

Binds a View to an item.

public abstract Presenter.ViewHolderonCreateViewHolder(ViewGroup parent)

Creates a new View.

protected voidonSelectLevelChanged(RowHeaderPresenter.ViewHolder holder)

Called when the select level changes.

public abstract voidonUnbindViewHolder(Presenter.ViewHolder viewHolder)

Unbinds a View from an item.

public voidsetNullItemVisibilityGone(boolean nullItemVisibilityGone)

Optionally sets the view visibility to View when bound to null.

public final voidsetSelectLevel(RowHeaderPresenter.ViewHolder holder, float selectLevel)

Sets the select level.

from PresentercancelAnimationsRecursive, getFacet, onBindViewHolder, onViewAttachedToWindow, onViewDetachedFromWindow, setFacet, setOnClickListener
from java.lang.Objectclone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructors

public RowHeaderPresenter()

Creates default RowHeaderPresenter using a title view and a description view.

See also: RowHeaderPresenter.ViewHolder

public RowHeaderPresenter(int layoutResourceId)

public RowHeaderPresenter(int layoutResourceId, boolean animateSelect)

Methods

public void setNullItemVisibilityGone(boolean nullItemVisibilityGone)

Optionally sets the view visibility to View when bound to null.

public boolean isNullItemVisibilityGone()

Returns true if the view visibility is set to View when bound to null.

public abstract Presenter.ViewHolder onCreateViewHolder(ViewGroup parent)

Creates a new View.

public abstract void onBindViewHolder(Presenter.ViewHolder viewHolder, java.lang.Object item)

Binds a View to an item.

public abstract void onUnbindViewHolder(Presenter.ViewHolder viewHolder)

Unbinds a View from an item. Any expensive references may be released here, and any fields that are not bound for every item should be cleared here.

public final void setSelectLevel(RowHeaderPresenter.ViewHolder holder, float selectLevel)

Sets the select level.

protected void onSelectLevelChanged(RowHeaderPresenter.ViewHolder holder)

Called when the select level changes. The default implementation sets the alpha on the view.

public int getSpaceUnderBaseline(RowHeaderPresenter.ViewHolder holder)

Returns the space (distance in pixels) below the baseline of the text view, if one exists; otherwise, returns 0.

protected static float getFontDescent(TextView textView, Paint fontMeasurePaint)

Source

/*
 * Copyright (C) 2014 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */
package androidx.leanback.widget;

import static androidx.annotation.RestrictTo.Scope.LIBRARY_GROUP_PREFIX;

import android.graphics.Paint;
import android.text.TextUtils;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

import androidx.annotation.RestrictTo;
import androidx.leanback.R;

/**
 * RowHeaderPresenter provides a default presentation for {@link HeaderItem} using a
 * {@link RowHeaderView} and optionally a TextView for description. If a subclass creates its own
 * view, the subclass must also override {@link #onCreateViewHolder(ViewGroup)},
 * {@link #onSelectLevelChanged(ViewHolder)}.
 */
public class RowHeaderPresenter extends Presenter {

    private final int mLayoutResourceId;
    private final Paint mFontMeasurePaint = new Paint(Paint.ANTI_ALIAS_FLAG);
    private boolean mNullItemVisibilityGone;
    private final boolean mAnimateSelect;

    /**
     * Creates default RowHeaderPresenter using a title view and a description view.
     * @see ViewHolder#ViewHolder(View)
     */
    public RowHeaderPresenter() {
        this(R.layout.lb_row_header);
    }

    /**
     * @hide
     */
    @RestrictTo(LIBRARY_GROUP_PREFIX)
    public RowHeaderPresenter(int layoutResourceId) {
        this(layoutResourceId, true);
    }

    /**
     * @hide
     */
    @RestrictTo(LIBRARY_GROUP_PREFIX)
    public RowHeaderPresenter(int layoutResourceId, boolean animateSelect) {
        mLayoutResourceId = layoutResourceId;
        mAnimateSelect = animateSelect;
    }

    /**
     * Optionally sets the view visibility to {@link View#GONE} when bound to null.
     */
    public void setNullItemVisibilityGone(boolean nullItemVisibilityGone) {
        mNullItemVisibilityGone = nullItemVisibilityGone;
    }

    /**
     * Returns true if the view visibility is set to {@link View#GONE} when bound to null.
     */
    public boolean isNullItemVisibilityGone() {
        return mNullItemVisibilityGone;
    }

    /**
     * A ViewHolder for the RowHeaderPresenter.
     */
    public static class ViewHolder extends Presenter.ViewHolder {
        float mSelectLevel;
        int mOriginalTextColor;
        float mUnselectAlpha;
        RowHeaderView mTitleView;
        TextView mDescriptionView;

        /**
         * Creating a new ViewHolder that supports title and description.
         * @param view Root of Views.
         */
        public ViewHolder(View view) {
            super(view);
            mTitleView = (RowHeaderView)view.findViewById(R.id.row_header);
            mDescriptionView = (TextView)view.findViewById(R.id.row_header_description);
            initColors();
        }

        /**
         * Uses a single {@link RowHeaderView} for creating a new ViewHolder.
         * @param view The single RowHeaderView.
         * @hide
         */
        @RestrictTo(LIBRARY_GROUP_PREFIX)
        public ViewHolder(RowHeaderView view) {
            super(view);
            mTitleView = view;
            initColors();
        }

        void initColors() {
            if (mTitleView != null) {
                mOriginalTextColor = mTitleView.getCurrentTextColor();
            }

            mUnselectAlpha = view.getResources().getFraction(
                    R.fraction.lb_browse_header_unselect_alpha, 1, 1);
        }

        public final float getSelectLevel() {
            return mSelectLevel;
        }
    }

    @Override
    public Presenter.ViewHolder onCreateViewHolder(ViewGroup parent) {
        View root = LayoutInflater.from(parent.getContext())
                .inflate(mLayoutResourceId, parent, false);

        ViewHolder viewHolder = new ViewHolder(root);
        if (mAnimateSelect) {
            setSelectLevel(viewHolder, 0);
        }
        return viewHolder;
    }

    @Override
    public void onBindViewHolder(Presenter.ViewHolder viewHolder, Object item) {
        HeaderItem headerItem = item == null ? null : ((Row) item).getHeaderItem();
        RowHeaderPresenter.ViewHolder vh = (RowHeaderPresenter.ViewHolder)viewHolder;
        if (headerItem == null) {
            if (vh.mTitleView != null) {
                vh.mTitleView.setText(null);
            }
            if (vh.mDescriptionView != null) {
                vh.mDescriptionView.setText(null);
            }

            viewHolder.view.setContentDescription(null);
            if (mNullItemVisibilityGone) {
                viewHolder.view.setVisibility(View.GONE);
            }
        } else {
            if (vh.mTitleView != null) {
                vh.mTitleView.setText(headerItem.getName());
            }
            if (vh.mDescriptionView != null) {
                if (TextUtils.isEmpty(headerItem.getDescription())) {
                    vh.mDescriptionView.setVisibility(View.GONE);
                } else {
                    vh.mDescriptionView.setVisibility(View.VISIBLE);
                }
                vh.mDescriptionView.setText(headerItem.getDescription());
            }
            viewHolder.view.setContentDescription(headerItem.getContentDescription());
            viewHolder.view.setVisibility(View.VISIBLE);
        }
    }

    @Override
    public void onUnbindViewHolder(Presenter.ViewHolder viewHolder) {
        RowHeaderPresenter.ViewHolder vh = (ViewHolder)viewHolder;
        if (vh.mTitleView != null) {
            vh.mTitleView.setText(null);
        }
        if (vh.mDescriptionView != null) {
            vh.mDescriptionView.setText(null);
        }

        if (mAnimateSelect) {
            setSelectLevel((ViewHolder) viewHolder, 0);
        }
    }

    /**
     * Sets the select level.
     */
    public final void setSelectLevel(ViewHolder holder, float selectLevel) {
        holder.mSelectLevel = selectLevel;
        onSelectLevelChanged(holder);
    }

    /**
     * Called when the select level changes.  The default implementation sets the alpha on the view.
     */
    protected void onSelectLevelChanged(ViewHolder holder) {
        if (mAnimateSelect) {
            holder.view.setAlpha(holder.mUnselectAlpha + holder.mSelectLevel
                    * (1f - holder.mUnselectAlpha));
        }
    }

    /**
     * Returns the space (distance in pixels) below the baseline of the
     * text view, if one exists; otherwise, returns 0.
     */
    public int getSpaceUnderBaseline(ViewHolder holder) {
        int space = holder.view.getPaddingBottom();
        if (holder.view instanceof TextView) {
            space += (int) getFontDescent((TextView) holder.view, mFontMeasurePaint);
        }
        return space;
    }

    @SuppressWarnings("ReferenceEquality")
    protected static float getFontDescent(TextView textView, Paint fontMeasurePaint) {
        if (fontMeasurePaint.getTextSize() != textView.getTextSize()) {
            fontMeasurePaint.setTextSize(textView.getTextSize());
        }
        if (fontMeasurePaint.getTypeface() != textView.getTypeface()) {
            fontMeasurePaint.setTypeface(textView.getTypeface());
        }
        return fontMeasurePaint.descent();
    }
}