com.medisa.myspacecal.QuickReturnFragment.java Source code

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Here is the source code for com.medisa.myspacecal.QuickReturnFragment.java

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/*
 * Copyright 2012 Roman Nurik + Nick Butcher
 *
 * 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.medisa.myspacecal;

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.view.ViewTreeObserver;
import android.widget.TextView;

import com.devspark.sidenavigation.sample.R;

public class QuickReturnFragment extends Fragment implements ObservableScrollView.Callbacks {
    private static final int STATE_ONSCREEN = 0;
    private static final int STATE_OFFSCREEN = 1;
    private static final int STATE_RETURNING = 2;

    private TextView mQuickReturnView;
    private View mPlaceholderView;
    private ObservableScrollView mObservableScrollView;
    private int mMinRawY = 0;
    private int mState = STATE_ONSCREEN;
    private int mQuickReturnHeight;
    private int mCachedVerticalScrollRange;

    public QuickReturnFragment() {
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        ViewGroup rootView = (ViewGroup) inflater.inflate(R.layout.fragment_content, container, false);

        mObservableScrollView = (ObservableScrollView) rootView.findViewById(R.id.scroll_view);
        mObservableScrollView.setCallbacks(this);

        mQuickReturnView = (TextView) rootView.findViewById(R.id.sticky);
        mQuickReturnView.setText(R.string.quick_return_item);
        mPlaceholderView = rootView.findViewById(R.id.placeholder);

        mObservableScrollView.getViewTreeObserver()
                .addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
                    @Override
                    public void onGlobalLayout() {
                        onScrollChanged();
                        mCachedVerticalScrollRange = mObservableScrollView.computeVerticalScrollRange();
                        mQuickReturnHeight = mQuickReturnView.getHeight();
                    }
                });

        return rootView;
    }

    @Override
    public void onScrollChanged() {
        int rawY = mPlaceholderView.getTop() - Math.min(
                mCachedVerticalScrollRange - mObservableScrollView.getHeight(), mObservableScrollView.getScrollY());
        int translationY = 0;

        switch (mState) {
        case STATE_OFFSCREEN:
            if (rawY <= mMinRawY) {
                mMinRawY = rawY;
            } else {
                mState = STATE_RETURNING;
            }
            translationY = rawY;
            break;

        case STATE_ONSCREEN:
            if (rawY < -mQuickReturnHeight) {
                mState = STATE_OFFSCREEN;
                mMinRawY = rawY;
            }
            translationY = rawY;
            break;

        case STATE_RETURNING:
            translationY = (rawY - mMinRawY) - mQuickReturnHeight;
            if (translationY > 0) {
                translationY = 0;
                mMinRawY = rawY - mQuickReturnHeight;
            }

            if (rawY > 0) {
                mState = STATE_ONSCREEN;
                translationY = rawY;
            }

            if (translationY < -mQuickReturnHeight) {
                mState = STATE_OFFSCREEN;
                mMinRawY = rawY;
            }
            break;
        }

        mQuickReturnView.setTranslationY(translationY);
    }
}