PrecomputedTextCompat

PrecomputedTextCompat

public PrecomputedTextCompat()

charAt

public char charAt(int index)

create

public static PrecomputedTextCompat create(
    @NonNull CharSequence text,
    @NonNull PrecomputedTextCompat.Params params
)

Create a new PrecomputedText which will pre-compute text measurement and glyph positioning information.

This can be expensive, so computing this on a background thread before your text will be presented can save work on the UI thread.

Note that any android.text.NoCopySpan attached to the text won't be passed to the created PrecomputedText.

getParagraphCount

public @IntRange(from = 0) int getParagraphCount()

Returns the count of paragraphs.

getParagraphEnd

public @IntRange(from = 0) int getParagraphEnd(@IntRange(from = 0) int paraIndex)

Returns the paragraph end offset of the text.

getParagraphStart

public @IntRange(from = 0) int getParagraphStart(@IntRange(from = 0) int paraIndex)

Returns the paragraph start offset of the text.

getParams

public @NonNull PrecomputedTextCompat.Params getParams()

Returns the parameters used to measure this text.

getSpanEnd

public int getSpanEnd(Object tag)

getSpanFlags

public int getSpanFlags(Object tag)

getSpanStart

public int getSpanStart(Object tag)

getSpans

public T[] <T> getSpans(int start, int end, Class<T> type)

getTextFuture

@UiThread
public static Future<PrecomputedTextCompat> getTextFuture(
    @NonNull CharSequence charSequence,
    @NonNull PrecomputedTextCompat.Params params,
    @Nullable Executor executor
)

Helper for PrecomputedText that returns a future to be used with setTextFuture. PrecomputedText is suited to compute on a background thread, but when TextView properties are dynamic, it's common to configure text properties and text at the same time, when binding a View. For example, in a RecyclerView Adapter:

    void onBindViewHolder(ViewHolder vh, int position) {
        ItemData data = getData(position);

        vh.textView.setTextSize(...);
        vh.textView.setFontVariationSettings(...);
        vh.textView.setText(data.text);
    }

In such cases, using PrecomputedText is difficult, since it isn't safe to defer the setText() code arbitrarily - a layout pass may happen before computation finishes, and will be incorrect if the text isn't ready yet.

With getTextFuture(), you can block on the result of the precomputation safely before the result is needed. AppCompatTextView provides setTextFuture for exactly this use case. With the following code, the app's layout work is largely done on a background thread:

    void onBindViewHolder(ViewHolder vh, int position) {
        ItemData data = getData(position);

        vh.textView.setTextSize(...);
        vh.textView.setFontVariationSettings(...);

        // start precompute
        Futurefuture = PrecomputedTextCompat.getTextFuture(
                data.text, vh.textView.getTextMetricsParamsCompat(), myExecutor);

        // and pass future to TextView, which awaits result before measuring
        vh.textView.setTextFuture(future);
    }

Because RecyclerView prefetches bind multiple frames in advance while scrolling, the text work generally has plenty of time to complete before measurement occurs.

Note: all TextView layout properties must be set before creating the Params object. If they are changed during the precomputation, this can cause a IllegalArgumentException when the precomputed value is consumed during measure, and doesn't reflect the TextView's current state.

length

public int length()

nextSpanTransition

public int nextSpanTransition(int start, int limit, Class type)

removeSpan

public void removeSpan(Object what)

setSpan

public void setSpan(Object what, int start, int end, int flags)

subSequence

public CharSequence subSequence(int start, int end)

toString

public @NonNull String toString()