PinnedOffsetView.java

/*
 * Copyright 2015 Google Inc.
 *
 * 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 io.plaidapp.ui.widget;

import android.content.Context;
import android.support.v4.view.ViewCompat;
import android.util.AttributeSet;
import android.view.View;

import io.plaidapp.R;

/**
 * A view which supports a minimum vertical offset (i.e. translation Y) and has a custom pinned
 * state.
 */
public class PinnedOffsetView extends View {

    private static final int[] STATE_PINNED = { R.attr.state_pinned };

    private int minOffset;
    private boolean isPinned = false;

    public PinnedOffsetView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public PinnedOffsetView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    public PinnedOffsetView(Context context, AttributeSet attrs, int defStyleAttr, int
            defStyleRes) {
        super(context, attrs, defStyleAttr, defStyleRes);
    }

    public void setOffset(int offset) {
        offset = Math.max(minOffset, offset);
        if (getTranslationY() != offset) {
            setTranslationY(offset);
            setPinned(offset == minOffset);
            ViewCompat.postInvalidateOnAnimation(this);
        }
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);
        minOffset = -(h - getMinimumHeight());
    }

    @Override
    public int[] onCreateDrawableState(int extraSpace) {
        final int[] drawableState = super.onCreateDrawableState(extraSpace + 1);
        if (isPinned) {
            mergeDrawableStates(drawableState, STATE_PINNED);
        }
        return drawableState;
    }

    public boolean isPinned() {
        return isPinned;
    }

    public void setPinned(boolean isPinned) {
        if (this.isPinned != isPinned) {
            this.isPinned = isPinned;
            refreshDrawableState();
        }
    }
}