Avoid churning NumberFormat instances in ProgressBar

Don't construct a new locale-specific NumberFormat every time a progress
bar's state is refreshed or updated.  We now do this only when necessary
due to a locale change.

Bug: 161264248
Test: atest ProgressBarTest
Change-Id: I349ec28268a3471184e5746b164f81428ad80cc8

1 files changed, 13 insertions, 2 deletions

diff --git a/core/java/android/widget/ProgressBar.java b/core/java/android/widget/ProgressBar.java
index 4b32e10d083b..35605c4c6f6e 100644
--- a/core/java/android/widget/ProgressBar.java
+++ b/core/java/android/widget/ProgressBar.java
@@ -69,6 +69,7 @@ import com.android.internal.R;
 
 import java.text.NumberFormat;
 import java.util.ArrayList;
+import java.util.Locale;
 
 /**
  * <p>
@@ -249,6 +250,9 @@ public class ProgressBar extends View {
 
     private ObjectAnimator mLastProgressAnimator;
 
+    private NumberFormat mPercentFormat;
+    private Locale mCachedLocale;
+
     /**
      * Create a new progress bar with range 0...100 and initial progress of 0.
      * @param context the application environment
@@ -1591,8 +1595,15 @@ public class ProgressBar extends View {
      * @return state description based on progress
      */
     private CharSequence formatStateDescription(int progress) {
-        return NumberFormat.getPercentInstance(mContext.getResources().getConfiguration().locale)
-                .format(getPercent(progress));
+        // Cache the locale-appropriate NumberFormat.  Configuration locale is guaranteed
+        // non-null, so the first time this is called we will always get the appropriate
+        // NumberFormat, then never regenerate it unless the locale changes on the fly.
+        final Locale curLocale = mContext.getResources().getConfiguration().getLocales().get(0);
+        if (!curLocale.equals(mCachedLocale)) {
+            mCachedLocale = curLocale;
+            mPercentFormat = NumberFormat.getPercentInstance(curLocale);
+        }
+        return mPercentFormat.format(getPercent(progress));
     }
 
     /**