FlexibleSpaceToolbarScrollViewActivity.java

/*
 * Copyright 2014 Soichiro Kashima
 *
 * 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.marshalchen.common.demoofui.observablescrollview;

import android.content.res.TypedArray;
import android.os.Build;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.support.v7.widget.Toolbar;
import android.util.TypedValue;
import android.view.View;
import android.view.ViewTreeObserver;
import android.widget.TextView;

import com.github.ksoichiro.android.observablescrollview.ObservableScrollView;
import com.github.ksoichiro.android.observablescrollview.ObservableScrollViewCallbacks;
import com.github.ksoichiro.android.observablescrollview.ScrollState;
import com.marshalchen.common.demoofui.R;
import com.nineoldandroids.view.ViewHelper;

public class FlexibleSpaceToolbarScrollViewActivity extends ActionBarActivity implements ObservableScrollViewCallbacks {

    private View mFlexibleSpaceView;
    private View mToolbarView;
    private TextView mTitleView;
    private int mFlexibleSpaceHeight;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.observable_scroll_view_activity_flexiblespacetoolbarscrollview);

        setSupportActionBar((Toolbar) findViewById(R.id.toolbar));
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);

        mFlexibleSpaceView = findViewById(R.id.flexible_space);
        mTitleView = (TextView) findViewById(R.id.title);
        mTitleView.setText(getTitle());
        setTitle(null);
        mToolbarView = findViewById(R.id.toolbar);

        final ObservableScrollView scrollView = (ObservableScrollView) findViewById(R.id.scroll);
        scrollView.setScrollViewCallbacks(this);

        mFlexibleSpaceHeight = getResources().getDimensionPixelSize(R.dimen.flexible_space_height);
        int flexibleSpaceAndToolbarHeight = mFlexibleSpaceHeight + getActionBarSize();

        findViewById(R.id.body).setPadding(0, flexibleSpaceAndToolbarHeight, 0, 0);
        mFlexibleSpaceView.getLayoutParams().height = flexibleSpaceAndToolbarHeight;

        ViewTreeObserver vto = mTitleView.getViewTreeObserver();
        vto.addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
            @Override
            public void onGlobalLayout() {
                if (Build.VERSION.SDK_INT < Build.VERSION_CODES.JELLY_BEAN) {
                    mTitleView.getViewTreeObserver().removeGlobalOnLayoutListener(this);
                } else {
                    mTitleView.getViewTreeObserver().removeOnGlobalLayoutListener(this);
                }
                updateFlexibleSpaceText(scrollView.getCurrentScrollY());
            }
        });
    }

    @Override
    public void onScrollChanged(int scrollY, boolean firstScroll, boolean dragging) {
        updateFlexibleSpaceText(scrollY);
    }

    @Override
    public void onDownMotionEvent() {
    }

    @Override
    public void onUpOrCancelMotionEvent(ScrollState scrollState) {
    }

    private void updateFlexibleSpaceText(final int scrollY) {
        ViewHelper.setTranslationY(mFlexibleSpaceView, -scrollY);
        int adjustedScrollY = scrollY;
        if (scrollY < 0) {
            adjustedScrollY = 0;
        } else if (mFlexibleSpaceHeight < scrollY) {
            adjustedScrollY = mFlexibleSpaceHeight;
        }
        float maxScale = (float) (mFlexibleSpaceHeight - mToolbarView.getHeight()) / mToolbarView.getHeight();
        float scale = maxScale * ((float) mFlexibleSpaceHeight - adjustedScrollY) / mFlexibleSpaceHeight;

        ViewHelper.setPivotX(mTitleView, 0);
        ViewHelper.setPivotY(mTitleView, 0);
        ViewHelper.setScaleX(mTitleView, 1 + scale);
        ViewHelper.setScaleY(mTitleView, 1 + scale);
        ViewHelper.setTranslationY(mTitleView, ViewHelper.getTranslationY(mFlexibleSpaceView) + mFlexibleSpaceView.getHeight() - mTitleView.getHeight() * (1 + scale));
        int maxTitleTranslationY = mToolbarView.getHeight() + mFlexibleSpaceHeight - (int) (mTitleView.getHeight() * (1 + scale));
        int titleTranslationY = (int) (maxTitleTranslationY * ((float) mFlexibleSpaceHeight - adjustedScrollY) / mFlexibleSpaceHeight);
        ViewHelper.setTranslationY(mTitleView, titleTranslationY);
    }

    private int getActionBarSize() {
        TypedValue typedValue = new TypedValue();
        int[] textSizeAttr = new int[]{R.attr.actionBarSize};
        int indexOfAttrTextSize = 0;
        TypedArray a = obtainStyledAttributes(typedValue.data, textSizeAttr);
        int actionBarSize = a.getDimensionPixelSize(indexOfAttrTextSize, -1);
        a.recycle();
        return actionBarSize;
    }
}