scroll animation max min

android/src/main/java/com/henninghall/date_picker/pickers/AndroidNative.java

@@ -1,21 +1,15 @@
 package com.henninghall.date_picker.pickers;
 
+import android.annotation.SuppressLint;
 import android.content.Context;
 import android.graphics.Paint;
-import android.os.Build;
-import android.support.annotation.RequiresApi;
+import android.os.Handler;
 import android.util.AttributeSet;
-import android.util.Log;
 import android.view.View;
 import android.widget.NumberPicker;
 
-import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
 
-import cn.carbswang.android.numberpickerview.library.NumberPickerView;
-
-import static android.widget.NumberPicker.OnScrollListener.SCROLL_STATE_IDLE;
-
 public class AndroidNative extends NumberPicker implements Picker {
 
     public AndroidNative(Context context) {
@@ -32,12 +26,6 @@ public class AndroidNative extends NumberPicker implements Picker {
 
     @Override
     public void setTextAlign(Paint.Align align) {
-
-    }
-
-    @Override
-    public void smoothScrollToValue(int value) {
-        setValue(value);
     }
 
     @Override
@@ -55,6 +43,75 @@ public class AndroidNative extends NumberPicker implements Picker {
 
     }
 
+    @Override
+    public void setShownCount(int count) {
+        // always 3 date rows -> nothing needs to be done here
+    }
+
+    @Override
+    public View getView() {
+        return this;
+    }
+
+
+    @Override
+    public void smoothScrollToValue(final int value) {
+        Handler handler = new Handler();
+        final AndroidNative self = this;
+
+        handler.postDelayed(new Runnable() {
+            public void run() {
+                int currentValue = self.getValue();
+                if (value == currentValue) return;
+                int shortestScrollOption = getShortestScrollOption(currentValue, value);
+                final int moves = Math.abs(shortestScrollOption);
+                for (int i = 0; i < moves; i++) {
+                    // need some delay between each scroll step to make sure it scrolls to correct value
+                    changeValueByOne(shortestScrollOption > 0, i * 100);
+                }
+            }
+            // since the SCROLL_STATE_IDLE event is dispatched before the wheel actually has stopped
+            // an extra delay has to be added before starting to scroll to correct value
+        }, 500);
+    }
+
+    private int getShortestScrollOption(int currentValue, int value){
+        final int maxValue = getMaxValue();
+        int option1 = value - currentValue;
+        int option2 = maxValue + 1 - Math.abs(option1);
+        if(getWrapSelectorWheel()){
+            return Math.abs(option1) < Math.abs(option2) ? option1 : option2;
+        }
+        if (currentValue + option1 > maxValue) return option2;
+        if (currentValue + option1 < 0) return option2;
+        return option1;
+    }
+
+    @SuppressLint("PrivateApi")
+    private void changeValueByOne(final NumberPicker higherPicker, final boolean increment) {
+        try {
+            Method method = getClass().getSuperclass().getDeclaredMethod("changeValueByOne", boolean.class);
+            method.setAccessible(true);
+            method.invoke(higherPicker, increment);
+        } catch (Exception  e) {
+            e.printStackTrace();
+            // make step without animation if failed to use reflection method
+            setValue((getValue() + (increment ? 1 : -1)) % getMaxValue());
+        }
+    }
+
+    private void changeValueByOne(final boolean increment, int ms) {
+        Handler handler = new Handler();
+        final AndroidNative self = this;
+        handler.postDelayed(new Runnable() {
+            @Override
+            public void run() {
+                changeValueByOne(self, increment);
+            }
+        }, ms);
+    }
+
+
     @Override
     public void setOnValueChangeListenerInScrolling(final OnValueChangeListenerInScrolling listener) {
         final Picker self = this;
@@ -70,23 +127,16 @@ public class AndroidNative extends NumberPicker implements Picker {
     public void setOnValueChangedListener(final Picker.OnValueChangeListener listener) {
         super.setOnScrollListener(new OnScrollListener() {
             int previousState = SCROLL_STATE_IDLE;
+
             @Override
             public void onScrollStateChange(NumberPicker numberPicker, int state) {
                 boolean stoppedScrolling = previousState != SCROLL_STATE_IDLE && state == SCROLL_STATE_IDLE;
-                if (stoppedScrolling) listener.onValueChange();
+                if (stoppedScrolling) {
+                    listener.onValueChange();
+                }
                 previousState = state;
             }
         });
     }
 
-
-    @Override
-    public void setShownCount(int count) {
-        // always 3 date rows -> nothing needs to be done here
-    }
-
-    @Override
-    public View getView() {
-        return this;
-    }
 }