Add IndicatingScrollView

2016-02-23 16:06:01 +08:00
1 parent a5856e67ee
commit 995146f60f
@@ -0,0 +1,92 @@
+/*
+ * Copyright (C) 2015 Hippo Seven
+ *
+ * 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 com.hippo.widget;
+
+import android.content.Context;
+import android.content.res.TypedArray;
+import android.graphics.Canvas;
+import android.graphics.Color;
+import android.graphics.Paint;
+import android.graphics.Rect;
+import android.support.annotation.NonNull;
+import android.util.AttributeSet;
+import android.widget.ScrollView;
+
+import com.hippo.ehviewer.R;
+
+public class IndicatingScrollView extends ScrollView {
+
+    private int mIndicatorHeight;
+
+    private final Paint mPaint = new Paint();
+    private final Rect mTemp = new Rect();
+
+    public IndicatingScrollView(Context context, AttributeSet attrs) {
+        super(context, attrs);
+        init(context, attrs);
+    }
+
+    public IndicatingScrollView(Context context, AttributeSet attrs, int defStyleAttr) {
+        super(context, attrs, defStyleAttr);
+        init(context, attrs);
+    }
+
+    private void init(Context context, AttributeSet attrs) {
+        TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.IndicatingScrollView);
+        mIndicatorHeight = a.getDimensionPixelOffset(R.styleable.IndicatingScrollView_indicatorHeight, 1);
+        mPaint.setColor(a.getColor(R.styleable.IndicatingScrollView_indicatorColor, Color.BLACK));
+        mPaint.setStyle(Paint.Style.FILL);
+        a.recycle();
+    }
+
+    private void fillTopIndicatorDrawRect() {
+        mTemp.set(0, 0, getWidth(), mIndicatorHeight);
+    }
+
+    private void fillBottomIndicatorDrawRect() {
+        mTemp.set(0, getHeight() - mIndicatorHeight, getWidth(), getHeight());
+    }
+
+    private boolean needShowTopIndicator() {
+        return canScrollVertically(-1);
+    }
+
+    private boolean needShowBottomIndicator() {
+        return canScrollVertically(1);
+    }
+
+    @Override
+    public void draw(@NonNull Canvas canvas) {
+        super.draw(canvas);
+
+        final int restoreCount = canvas.save();
+        canvas.translate(getScrollX(), getScrollY());
+
+        // Draw top indicator
+        if (needShowTopIndicator()) {
+            fillTopIndicatorDrawRect();
+            canvas.drawRect(mTemp, mPaint);
+        }
+        // Draw bottom indicator
+        if (needShowBottomIndicator()) {
+            fillBottomIndicatorDrawRect();
+            canvas.drawRect(mTemp, mPaint);
+        }
+
+        canvas.restoreToCount(restoreCount);
+    }
+}