FlexibleSpaceWithImageListViewActivity.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.graphics.Color;
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.widget.AbsListView;
import android.widget.ArrayAdapter;
import android.widget.TextView;

import com.github.ksoichiro.android.observablescrollview.ObservableListView;
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;
import com.nineoldandroids.view.ViewPropertyAnimator;

import java.util.ArrayList;
import java.util.List;

public class FlexibleSpaceWithImageListViewActivity extends ActionBarActivity implements ObservableScrollViewCallbacks {

    private static final float MAX_TEXT_SCALE_DELTA = 0.3f;
    private static final boolean TOOLBAR_IS_STICKY = false;

    private View mToolbar;
    private View mImageView;
    private View mOverlayView;
    private View mListBackgroundView;
    private TextView mTitleView;
    private View mFab;
    private int mActionBarSize;
    private int mFlexibleSpaceShowFabOffset;
    private int mFlexibleSpaceImageHeight;
    private int mFabMargin;
    private int mToolbarColor;
    private boolean mFabIsShown;

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

        setSupportActionBar((Toolbar) findViewById(R.id.toolbar));

        mFlexibleSpaceImageHeight = getResources().getDimensionPixelSize(R.dimen.flexible_space_image_height);
        mFlexibleSpaceShowFabOffset = getResources().getDimensionPixelSize(R.dimen.flexible_space_show_fab_offset);
        mActionBarSize = getActionBarSize();
        mToolbarColor = getResources().getColor(R.color.primary);

        mToolbar = findViewById(R.id.toolbar);
        if (!TOOLBAR_IS_STICKY) {
            mToolbar.setBackgroundColor(Color.TRANSPARENT);
        }
        mImageView = findViewById(R.id.image);
        mOverlayView = findViewById(R.id.overlay);
        ObservableListView listView = (ObservableListView) findViewById(R.id.list);
        listView.setScrollViewCallbacks(this);

        // Set padding view for ListView. This is the flexible space.
        View paddingView = new View(this);
        AbsListView.LayoutParams lp = new AbsListView.LayoutParams(AbsListView.LayoutParams.MATCH_PARENT,
                mFlexibleSpaceImageHeight);
        paddingView.setLayoutParams(lp);

        // This is required to disable header's list selector effect
        paddingView.setClickable(true);

        listView.addHeaderView(paddingView);
        List<String> items = new ArrayList<String>();
        for (int i = 1; i <= 100; i++) {
            items.add("Item " + i);
        }
        listView.setAdapter(new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, items));
        mTitleView = (TextView) findViewById(R.id.title);
        mTitleView.setText(getTitle());
        setTitle(null);
        mFab = findViewById(R.id.fab);
        mFabMargin = getResources().getDimensionPixelSize(R.dimen.margin_standard);
        ViewHelper.setScaleX(mFab, 0);
        ViewHelper.setScaleY(mFab, 0);

        // mListBackgroundView makes ListView's background except header view.
        mListBackgroundView = findViewById(R.id.list_background);
        final View contentView = getWindow().getDecorView().findViewById(android.R.id.content);
        contentView.post(new Runnable() {
            @Override
            public void run() {
                // mListBackgroundView's should fill its parent vertically
                // but the height of the content view is 0 on 'onCreate'.
                // So we should get it with post().
                mListBackgroundView.getLayoutParams().height = contentView.getHeight();
            }
        });
    }

    @Override
    public void onScrollChanged(int scrollY, boolean firstScroll, boolean dragging) {
        // Translate overlay and image
        float flexibleRange = mFlexibleSpaceImageHeight - mActionBarSize;
        int minOverlayTransitionY = mActionBarSize - mOverlayView.getHeight();
        ViewHelper.setTranslationY(mOverlayView, Math.max(minOverlayTransitionY, Math.min(0, -scrollY)));
        ViewHelper.setTranslationY(mImageView, Math.max(minOverlayTransitionY, Math.min(0, -scrollY / 2)));

        // Translate list background
        ViewHelper.setTranslationY(mListBackgroundView, Math.max(0, -scrollY + mFlexibleSpaceImageHeight));

        // Change alpha of overlay
        ViewHelper.setAlpha(mOverlayView, Math.max(0, Math.min(1, (float) scrollY / flexibleRange)));

        // Scale title text
        float scale = 1 + Math.max(0, Math.min(MAX_TEXT_SCALE_DELTA, (flexibleRange - scrollY) / flexibleRange));
        ViewHelper.setPivotX(mTitleView, 0);
        ViewHelper.setPivotY(mTitleView, 0);
        ViewHelper.setScaleX(mTitleView, scale);
        ViewHelper.setScaleY(mTitleView, scale);

        // Translate title text
        int maxTitleTranslationY = (int) (mFlexibleSpaceImageHeight - mTitleView.getHeight() * scale);
        int titleTranslationY = maxTitleTranslationY - scrollY;
        if (TOOLBAR_IS_STICKY) {
            titleTranslationY = Math.max(0, titleTranslationY);
        }
        ViewHelper.setTranslationY(mTitleView, titleTranslationY);

        // Translate FAB
        int maxFabTranslationY = mFlexibleSpaceImageHeight - mFab.getHeight() / 2;
        int fabTranslationY = Math.max(mActionBarSize - mFab.getHeight() / 2,
                Math.min(maxFabTranslationY, -scrollY + mFlexibleSpaceImageHeight - mFab.getHeight() / 2));
        ViewHelper.setTranslationX(mFab, mOverlayView.getWidth() - mFabMargin - mFab.getWidth());
        ViewHelper.setTranslationY(mFab, fabTranslationY);

        // Show/hide FAB
        if (ViewHelper.getTranslationY(mFab) < mFlexibleSpaceShowFabOffset) {
            hideFab();
        } else {
            showFab();
        }

        if (TOOLBAR_IS_STICKY) {
            // Change alpha of toolbar background
            if (-scrollY + mFlexibleSpaceImageHeight <= mActionBarSize) {
                setBackgroundAlpha(mToolbar, 1, mToolbarColor);
            } else {
                setBackgroundAlpha(mToolbar, 0, mToolbarColor);
            }
        } else {
            // Translate Toolbar
            if (scrollY < mFlexibleSpaceImageHeight) {
                ViewHelper.setTranslationY(mToolbar, 0);
            } else {
                ViewHelper.setTranslationY(mToolbar, -scrollY);
            }
        }
    }

    @Override
    public void onDownMotionEvent() {
    }

    @Override
    public void onUpOrCancelMotionEvent(ScrollState scrollState) {
    }

    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;
    }

    private void showFab() {
        if (!mFabIsShown) {
            ViewPropertyAnimator.animate(mFab).cancel();
            ViewPropertyAnimator.animate(mFab).scaleX(1).scaleY(1).setDuration(200).start();
            mFabIsShown = true;
        }
    }

    private void hideFab() {
        if (mFabIsShown) {
            ViewPropertyAnimator.animate(mFab).cancel();
            ViewPropertyAnimator.animate(mFab).scaleX(0).scaleY(0).setDuration(200).start();
            mFabIsShown = false;
        }
    }

    private void setBackgroundAlpha(View view, float alpha, int baseColor) {
        int a = Math.min(255, Math.max(0, (int) (alpha * 255))) << 24;
        int rgb = 0x00ffffff & baseColor;
        view.setBackgroundColor(a + rgb);
    }
}