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      1 /*
      2  * Copyright 2012 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *     http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package com.example.android.animationsdemo;
     18 
     19 import android.animation.Animator;
     20 import android.animation.AnimatorListenerAdapter;
     21 import android.app.Activity;
     22 import android.content.Intent;
     23 import android.os.Bundle;
     24 import android.support.v4.app.NavUtils;
     25 import android.view.Menu;
     26 import android.view.MenuItem;
     27 import android.view.View;
     28 
     29 /**
     30  * This sample demonstrates cross-fading between two overlapping views.
     31  *
     32  * <p>In this sample, the two overlapping views are a loading indicator and some text content. The
     33  * active view is toggled by touching the toggle button in the action bar. In real-world
     34  * applications, this toggle would occur as soon as content was available. Note that if content is
     35  * immediately available, a loading spinner shouldn't be presented and there should be no
     36  * animation.</p>
     37  */
     38 public class CrossfadeActivity extends Activity {
     39     /**
     40      * The flag indicating whether content is loaded (text is shown) or not (loading spinner is
     41      * shown).
     42      */
     43     private boolean mContentLoaded;
     44 
     45     /**
     46      * The view (or view group) containing the content. This is one of two overlapping views.
     47      */
     48     private View mContentView;
     49 
     50     /**
     51      * The view containing the loading indicator. This is the other of two overlapping views.
     52      */
     53     private View mLoadingView;
     54 
     55     /**
     56      * The system "short" animation time duration, in milliseconds. This duration is ideal for
     57      * subtle animations or animations that occur very frequently.
     58      */
     59     private int mShortAnimationDuration;
     60 
     61     @Override
     62     protected void onCreate(Bundle savedInstanceState) {
     63         super.onCreate(savedInstanceState);
     64         setContentView(R.layout.activity_crossfade);
     65 
     66         mContentView = findViewById(R.id.content);
     67         mLoadingView = findViewById(R.id.loading_spinner);
     68 
     69         // Initially hide the content view.
     70         mContentView.setVisibility(View.GONE);
     71 
     72         // Retrieve and cache the system's default "short" animation time.
     73         mShortAnimationDuration = getResources().getInteger(android.R.integer.config_shortAnimTime);
     74     }
     75 
     76     @Override
     77     public boolean onCreateOptionsMenu(Menu menu) {
     78         super.onCreateOptionsMenu(menu);
     79         getMenuInflater().inflate(R.menu.activity_crossfade, menu);
     80         return true;
     81     }
     82 
     83     @Override
     84     public boolean onOptionsItemSelected(MenuItem item) {
     85         switch (item.getItemId()) {
     86             case android.R.id.home:
     87                 // Navigate "up" the demo structure to the launchpad activity.
     88                 // See http://developer.android.com/design/patterns/navigation.html for more.
     89                 NavUtils.navigateUpTo(this, new Intent(this, MainActivity.class));
     90                 return true;
     91 
     92             case R.id.action_toggle:
     93                 // Toggle whether content is loaded.
     94                 mContentLoaded = !mContentLoaded;
     95                 showContentOrLoadingIndicator(mContentLoaded);
     96                 return true;
     97         }
     98 
     99         return super.onOptionsItemSelected(item);
    100     }
    101 
    102     /**
    103      * Cross-fades between {@link #mContentView} and {@link #mLoadingView}.
    104      */
    105     private void showContentOrLoadingIndicator(boolean contentLoaded) {
    106         // Decide which view to hide and which to show.
    107         final View showView = contentLoaded ? mContentView : mLoadingView;
    108         final View hideView = contentLoaded ? mLoadingView : mContentView;
    109 
    110         // Set the "show" view to 0% opacity but visible, so that it is visible
    111         // (but fully transparent) during the animation.
    112         showView.setAlpha(0f);
    113         showView.setVisibility(View.VISIBLE);
    114 
    115         // Animate the "show" view to 100% opacity, and clear any animation listener set on
    116         // the view. Remember that listeners are not limited to the specific animation
    117         // describes in the chained method calls. Listeners are set on the
    118         // ViewPropertyAnimator object for the view, which persists across several
    119         // animations.
    120         showView.animate()
    121                 .alpha(1f)
    122                 .setDuration(mShortAnimationDuration)
    123                 .setListener(null);
    124 
    125         // Animate the "hide" view to 0% opacity. After the animation ends, set its visibility
    126         // to GONE as an optimization step (it won't participate in layout passes, etc.)
    127         hideView.animate()
    128                 .alpha(0f)
    129                 .setDuration(mShortAnimationDuration)
    130                 .setListener(new AnimatorListenerAdapter() {
    131                     @Override
    132                     public void onAnimationEnd(Animator animation) {
    133                         hideView.setVisibility(View.GONE);
    134                     }
    135                 });
    136     }
    137 }
    138