[Slider] Fix the validation of the slider step size and values.

Resolves #1587 PiperOrigin-RevId: 327419448 (cherry picked from commit 5004d5a)
material-components · Aug 28, 2020 · 194a0aa · ansman · Sep 2, 2020 · 194a0aa
1 parent 475e63b
commit 194a0aa
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Showing 2 changed files with 59 additions and 2 deletions.
diff --git a/lib/java/com/google/android/material/slider/BaseSlider.java b/lib/java/com/google/android/material/slider/BaseSlider.java
@@ -82,6 +82,8 @@
 import com.google.android.material.tooltip.TooltipDrawable;
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
+import java.math.BigDecimal;
+import java.math.MathContext;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.Iterator;
@@ -456,8 +458,21 @@ private void validateValueTo() {
     }
   }
 
+  private boolean valueLandsOnTick(float value) {
+    // Check that the value is a multiple of stepSize given the offset of valueFrom
+    // We're using BigDecimal here to avoid floating point rounding errors.
+    double potentialTickValue =
+        new BigDecimal(Float.toString(value))
+            .subtract(new BigDecimal(Float.toString(valueFrom)))
+            .divide(new BigDecimal(Float.toString(stepSize)), MathContext.DECIMAL64)
+            .doubleValue();
+
+    // If the potentialTickValue is a whole number, it means the value lands on a tick.
+    return Math.abs(Math.round(potentialTickValue) - potentialTickValue) < THRESHOLD;
+  }
+
   private void validateStepSize() {
-    if (stepSize > 0.0f && ((valueTo - valueFrom) / stepSize) % 1 > THRESHOLD) {
+    if (stepSize > 0.0f && !valueLandsOnTick(valueTo)) {
       throw new IllegalStateException(
           String.format(
               EXCEPTION_ILLEGAL_STEP_SIZE,
@@ -477,7 +492,7 @@ private void validateValues() {
                 Float.toString(valueFrom),
                 Float.toString(valueTo)));
       }
-      if (stepSize > 0.0f && ((valueFrom - value) / stepSize) % 1 > THRESHOLD) {
+      if (stepSize > 0.0f && !valueLandsOnTick(value)) {
         throw new IllegalStateException(
             String.format(
                 EXCEPTION_ILLEGAL_DISCRETE_VALUE,

diff --git a/lib/javatests/com/google/android/material/slider/SliderConfigTest.java b/lib/javatests/com/google/android/material/slider/SliderConfigTest.java
@@ -119,6 +119,48 @@ public static Iterable<Object[]> data() {
           /* stepValue = */ 10f,
           /* value = */ 21f,
           IllegalStateException.class,
+        },
+        new Object[] {
+          /* valueFrom = */ 0.1f,
+          /* valueTo = */ 10f,
+          /* stepValue = */ 0.1f,
+          /* value = */ 0.1f,
+          null,
+        },
+        new Object[] {
+          /* valueFrom = */ 0.1f,
+          /* valueTo = */ 10f,
+          /* stepValue = */ 0.1f,
+          /* value = */ 0.1999999f, // We don't support this level of precision.
+          null,
+        },
+        new Object[] {
+          /* valueFrom = */ 0f,
+          /* valueTo = */ 10f,
+          /* stepValue = */ 0.001f,
+          /* value = */ 7f,
+          null,
+        },
+        new Object[] {
+          /* valueFrom = */ 0.1f,
+          /* valueTo = */ 10f,
+          /* stepValue = */ 0.1f,
+          /* value = */ 0.15f,
+          IllegalStateException.class,
+        },
+        new Object[] {
+          /* valueFrom = */ 0f,
+          /* valueTo = */ 100000f,
+          /* stepValue = */ 0.01f,
+          /* value = */ 65536.02f,
+          null,
+        },
+        new Object[] {
+          /* valueFrom = */ 0f,
+          /* valueTo = */ 1f,
+          /* stepValue = */ 1 / 3f,
+          /* value = */ 0f,
+          null,
         });
   }