JellyBeanSpanFixTextView.java

// Copyright 2012 Pierre-Yves Ricau
// 
// 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 info.piwai.android;

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

import android.content.Context;
import android.text.SpannableStringBuilder;
import android.text.Spanned;
import android.util.AttributeSet;
import android.util.Log;
import android.widget.TextView;

/**
 * <p>
 * A {@link TextView} that insert spaces around its text spans where needed to
 * prevent {@link IndexOutOfBoundsException} in {@link #onMeasure(int, int)} on
 * Jelly Bean.
 * <p>
 * When {@link #onMeasure(int, int)} throws an exception, we try to fix the text
 * by adding spaces around spans, until it works again. We then try removing
 * some of the added spans, to minimize the insertions.
 * <p>
 * The fix is time consuming (a few ms, it depends on the size of your text),
 * but it should only happen once per text change.
 * <p>
 * See http://code.google.com/p/android/issues/detail?id=35466
 * 
 * @author "Pierre-Yves Ricau" <[email protected]>
 * 
 */
public class JellyBeanSpanFixTextView extends TextView {

	private static class FixingResult {
		public final boolean fixed;
		public final List<Object> spansWithSpacesBefore;
		public final List<Object> spansWithSpacesAfter;

		public static FixingResult fixed(List<Object> spansWithSpacesBefore, List<Object> spansWithSpacesAfter) {
			return new FixingResult(true, spansWithSpacesBefore, spansWithSpacesAfter);
		}

		public static FixingResult notFixed() {
			return new FixingResult(false, null, null);
		}

		private FixingResult(boolean fixed, List<Object> spansWithSpacesBefore, List<Object> spansWithSpacesAfter) {
			this.fixed = fixed;
			this.spansWithSpacesBefore = spansWithSpacesBefore;
			this.spansWithSpacesAfter = spansWithSpacesAfter;
		}
	}

	private static final String TAG = JellyBeanSpanFixTextView.class.getSimpleName();

	public JellyBeanSpanFixTextView(Context context, AttributeSet attrs, int defStyle) {
		super(context, attrs, defStyle);
	}

	public JellyBeanSpanFixTextView(Context context, AttributeSet attrs) {
		super(context, attrs);
	}

	public JellyBeanSpanFixTextView(Context context) {
		super(context);
	}

	@Override
	protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
		try {
			super.onMeasure(widthMeasureSpec, heightMeasureSpec);
		} catch (IndexOutOfBoundsException e) {
			fixOnMeasure(widthMeasureSpec, heightMeasureSpec);
		}
	}

	/**
	 * If possible, fixes the Spanned text by adding spaces around spans when
	 * needed.
	 */
	private void fixOnMeasure(int widthMeasureSpec, int heightMeasureSpec) {
		CharSequence text = getText();
		if (text instanceof Spanned) {
			SpannableStringBuilder builder = new SpannableStringBuilder(text);
			fixSpannedWithSpaces(builder, widthMeasureSpec, heightMeasureSpec);
		} else {
			if (BuildConfig.DEBUG) {
				Log.d(TAG, "The text isn't a Spanned");
			}
			fallbackToString(widthMeasureSpec, heightMeasureSpec);
		}
	}

	/**
	 * Add spaces around spans until the text is fixed, and then removes the
	 * unneeded spaces
	 */
	private void fixSpannedWithSpaces(SpannableStringBuilder builder, int widthMeasureSpec, int heightMeasureSpec) {
		long startFix = System.currentTimeMillis();

		FixingResult result = addSpacesAroundSpansUntilFixed(builder, widthMeasureSpec, heightMeasureSpec);

		if (result.fixed) {
			removeUnneededSpaces(widthMeasureSpec, heightMeasureSpec, builder, result);
		} else {
			fallbackToString(widthMeasureSpec, heightMeasureSpec);
		}

		if (BuildConfig.DEBUG) {
			long fixDuration = System.currentTimeMillis() - startFix;
			Log.d(TAG, "fixSpannedWithSpaces() duration in ms: " + fixDuration);
		}
	}

	private FixingResult addSpacesAroundSpansUntilFixed(SpannableStringBuilder builder, int widthMeasureSpec, int heightMeasureSpec) {

		Object[] spans = builder.getSpans(0, builder.length(), Object.class);
		List<Object> spansWithSpacesBefore = new ArrayList<Object>(spans.length);
		List<Object> spansWithSpacesAfter = new ArrayList<Object>(spans.length);

		for (Object span : spans) {
			int spanStart = builder.getSpanStart(span);
			if (isNotSpace(builder, spanStart - 1)) {
				builder.insert(spanStart, " ");
				spansWithSpacesBefore.add(span);
			}

			int spanEnd = builder.getSpanEnd(span);
			if (isNotSpace(builder, spanEnd)) {
				builder.insert(spanEnd, " ");
				spansWithSpacesAfter.add(span);
			}

			try {
				setTextAndMeasure(builder, widthMeasureSpec, heightMeasureSpec);
				return FixingResult.fixed(spansWithSpacesBefore, spansWithSpacesAfter);
			} catch (IndexOutOfBoundsException notFixed) {
			}
		}
		if (BuildConfig.DEBUG) {
			Log.d(TAG, "Could not fix the Spanned by adding spaces around spans");
		}
		return FixingResult.notFixed();
	}

	private boolean isNotSpace(CharSequence text, int where) {
		return text.charAt(where) != ' ';
	}

	private void setTextAndMeasure(CharSequence text, int widthMeasureSpec, int heightMeasureSpec) {
		setText(text);
		super.onMeasure(widthMeasureSpec, heightMeasureSpec);
	}

	private void removeUnneededSpaces(int widthMeasureSpec, int heightMeasureSpec, SpannableStringBuilder builder, FixingResult result) {

		for (Object span : result.spansWithSpacesAfter) {
			int spanEnd = builder.getSpanEnd(span);
			builder.delete(spanEnd, spanEnd + 1);
			try {
				setTextAndMeasure(builder, widthMeasureSpec, heightMeasureSpec);
			} catch (IndexOutOfBoundsException ignored) {
				builder.insert(spanEnd, " ");
			}
		}

		boolean needReset = true;
		for (Object span : result.spansWithSpacesBefore) {
			int spanStart = builder.getSpanStart(span);
			builder.delete(spanStart - 1, spanStart);
			try {
				setTextAndMeasure(builder, widthMeasureSpec, heightMeasureSpec);
				needReset = false;
			} catch (IndexOutOfBoundsException ignored) {
				needReset = true;
				int newSpanStart = spanStart - 1;
				builder.insert(newSpanStart, " ");
			}
		}

		if (needReset) {
			setText(builder);
			super.onMeasure(widthMeasureSpec, heightMeasureSpec);
		}
	}

	private void fallbackToString(int widthMeasureSpec, int heightMeasureSpec) {
		if (BuildConfig.DEBUG) {
			Log.d(TAG, "Fallback to unspanned text");
		}
		String fallbackText = getText().toString();
		setTextAndMeasure(fallbackText, widthMeasureSpec, heightMeasureSpec);
	}

}