EllipsizedTextView.java

/*
 * Copyright 2016 Gleb Godonoga.
 *
 * 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 com.andrada.sitracker.ui.widget;

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.text.Layout;
import android.text.StaticLayout;
import android.text.TextUtils;
import android.util.AttributeSet;
import android.widget.TextView;

import org.jetbrains.annotations.NotNull;

import java.util.ArrayList;
import java.util.List;

/**
 * A simple {@link android.widget.TextView} subclass that uses {@link android.text.TextUtils#ellipsize(CharSequence,
 * android.text.TextPaint, float, android.text.TextUtils.TruncateAt, boolean,
 * android.text.TextUtils.EllipsizeCallback)} to truncate the displayed text. This is used in
 * {@link com.andrada.sitracker.ui.components.PublicationItemView} when displaying publication description
 * which is converted from HTML to a {@link android.text.SpannableString} and sometimes causes
 * issues for the built-in TextView ellipsize function.
 */
public class EllipsizedTextView extends TextView {

    private static final String ELLIPSIS = "...";
    private final List<EllipsizeListener> ellipsizeListeners = new ArrayList<EllipsizeListener>();
    private boolean isEllipsized;
    private boolean isStale;
    private boolean programmaticChange;
    private String fullText;
    private int maxLines = -1;
    private float lineSpacingMultiplier = 1.0f;
    private float lineAdditionalVerticalPadding = 0.0f;

    public EllipsizedTextView(@NotNull Context context) {
        this(context, null, 0);
    }

    public EllipsizedTextView(@NotNull Context context, @NotNull AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public EllipsizedTextView(@NotNull Context context, @NotNull AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);

        // Attribute initialization
        final TypedArray a = context.obtainStyledAttributes(attrs, new int[]{
                android.R.attr.maxLines
        }, defStyle, 0);
        maxLines = a.getInteger(0, 2);
        a.recycle();
    }

    public void addEllipsizeListener(EllipsizeListener listener) {
        if (listener == null) {
            throw new NullPointerException();
        }
        ellipsizeListeners.add(listener);
    }

    public void removeEllipsizeListener(EllipsizeListener listener) {
        ellipsizeListeners.remove(listener);
    }

    public boolean isEllipsized() {
        return isEllipsized;
    }

    private void resetText() {
        int maxLines = getMaxLines();
        String workingText = fullText;
        boolean ellipsized = false;
        if (maxLines != -1) {
            Layout layout = createWorkingLayout(workingText);
            if (layout.getLineCount() > maxLines) {
                workingText = fullText.substring(0, layout.getLineEnd(maxLines - 1)).trim();
                while (createWorkingLayout(workingText + ELLIPSIS).getLineCount() > maxLines) {
                    int lastSpace = workingText.lastIndexOf(' ');
                    if (lastSpace == -1) {
                        break;
                    }
                    workingText = workingText.substring(0, lastSpace);
                }
                workingText = workingText + ELLIPSIS;
                ellipsized = true;
            }
        }
        if (!workingText.equals(getText())) {
            programmaticChange = true;
            try {
                setText(workingText);
            } finally {
                programmaticChange = false;
            }
        }
        isStale = false;
        if (ellipsized != isEllipsized) {
            isEllipsized = ellipsized;
            for (EllipsizeListener listener : ellipsizeListeners) {
                listener.ellipsizeStateChanged(ellipsized);
            }
        }
    }

    @Override
    protected void onDraw(Canvas canvas) {
        if (isStale) {
            super.setEllipsize(null);
            resetText();
        }
        super.onDraw(canvas);
    }

    private Layout createWorkingLayout(String workingText) {
        return new StaticLayout(workingText, getPaint(), getWidth() - getPaddingLeft() - getPaddingRight(),
                Layout.Alignment.ALIGN_NORMAL, lineSpacingMultiplier, lineAdditionalVerticalPadding, false);
    }

    public interface EllipsizeListener {
        void ellipsizeStateChanged(boolean ellipsized);
    }

    @Override
    public void setMaxLines(int maxLines) {
        super.setMaxLines(maxLines);
        this.maxLines = maxLines;
        isStale = true;
    }


    public int getMaxLines() {
        return maxLines;
    }

    @Override
    public void setEllipsize(TextUtils.TruncateAt where) {
        // Ellipsize settings are not respected
    }

    @Override
    public void setLineSpacing(float add, float mult) {
        this.lineAdditionalVerticalPadding = add;
        this.lineSpacingMultiplier = mult;
        super.setLineSpacing(add, mult);
    }


    @Override
    protected void onTextChanged(CharSequence text, int start, int before, int after) {
        super.onTextChanged(text, start, before, after);
        if (!programmaticChange) {
            fullText = text.toString();
            isStale = true;
        }
    }


}