【Android】Animation动画（二）
Displaying Card Flip Animations
This lesson shows you how to do a card flip animation with custom fragment animations. Card flips animate between views of content by showing an animation that emulates a card flipping over.（说白了就是界面切换，只不过View是通过Fragment实现的）上代码：
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.app.Activity;
20 import android.app.Fragment;
21 import android.app.FragmentManager;
22 import android.content.Intent;
23 import android.os.Bundle;
24 import android.os.Handler;
25 import android.support.v4.app.NavUtils;
26 import android.view.LayoutInflater;
27 import android.view.Menu;
28 import android.view.MenuItem;
29 import android.view.View;
30 import android.view.ViewGroup;
31 import android.widget.TextView;
32
33 /**
34 * Demonstrates a "card-flip" animation using custom fragment transactions ({@link
35 * android.app.FragmentTransaction#setCustomAnimations(int, int)}).
36 *
37 * <p>This sample shows an "info" action bar button that shows the back of a "card", rotating the
38 * front of the card out and the back of the card in. The reverse animation is played when the user
39 * presses the system Back button or the "photo" action bar button.</p>
40 */
41 public class CardFlipActivity extends Activity
42 implements FragmentManager.OnBackStackChangedListener {
43 /**
44 * A handler object, used for deferring UI operations.
45 */
46 private Handler mHandler = new Handler();
47
48 /**
49 * Whether or not we're showing the back of the card (otherwise showing the front).
50 */
51 private boolean mShowingBack = false;
52
53 @Override
54 protected void onCreate(Bundle savedInstanceState) {
55 super.onCreate(savedInstanceState);
56 setContentView(R.layout.activity_card_flip);
57
58 if (savedInstanceState == null) {
59 // If there is no saved instance state, add a fragment representing the
60 // front of the card to this activity. If there is saved instance state,
61 // this fragment will have already been added to the activity.
62 getFragmentManager()
63 .beginTransaction()
64 .add(R.id.container, new CardFrontFragment())
65 .commit();
66 } else {
67 mShowingBack = (getFragmentManager().getBackStackEntryCount() > 0);
68 }
69
70 // Monitor back stack changes to ensure the action bar shows the appropriate
71 // button (either "photo" or "info").
72 getFragmentManager().addOnBackStackChangedListener(this);
73 }
74
75 @Override
76 public boolean onCreateOptionsMenu(Menu menu) {
77 super.onCreateOptionsMenu(menu);
78
79 // Add either a "photo" or "finish" button to the action bar, depending on which page
80 // is currently selected.
81 MenuItem item = menu.add(Menu.NONE, R.id.action_flip, Menu.NONE,
82 mShowingBack
83 ? R.string.action_photo
84 : R.string.action_info);
85 item.setIcon(mShowingBack
86 ? R.drawable.ic_action_photo
87 : R.drawable.ic_action_info);
88 item.setShowAsAction(MenuItem.SHOW_AS_ACTION_IF_ROOM);
89 return true;
90 }
91
92 @Override
93 public boolean onOptionsItemSelected(MenuItem item) {
94 switch (item.getItemId()) {
95 case android.R.id.home:
96 // Navigate "up" the demo structure to the launchpad activity.
97 // See http://developer.android.com/design/patterns/navigation.html for more.
98 NavUtils.navigateUpTo(this, new Intent(this, MainActivity.class));
99 return true;
100
101 case R.id.action_flip:
102 flipCard();
103 return true;
104 }
105
106 return super.onOptionsItemSelected(item);
107 }
108
109 private void flipCard() {
110 if (mShowingBack) {
111 getFragmentManager().popBackStack();
112 return;
113 }
114
115 // Flip to the back.
116
117 mShowingBack = true;
118
119 // Create and commit a new fragment transaction that adds the fragment for the back of
120 // the card, uses custom animations, and is part of the fragment manager's back stack.
121
122 getFragmentManager()
123 .beginTransaction()
124
125 // Replace the default fragment animations with animator resources representing
126 // rotations when switching to the back of the card, as well as animator
127 // resources representing rotations when flipping back to the front (e.g. when
128 // the system Back button is pressed).
129 .setCustomAnimations(
130 R.animator.card_flip_right_in, R.animator.card_flip_right_out,
131 R.animator.card_flip_left_in, R.animator.card_flip_left_out)
132
133 // Replace any fragments currently in the container view with a fragment
134 // representing the next page (indicated by the just-incremented currentPage
135 // variable).
136 .replace(R.id.container, new CardBackFragment())
137
138 // Add this transaction to the back stack, allowing users to press Back
139 // to get to the front of the card.
140 .addToBackStack(null)
141
142 // Commit the transaction.
143 .commit();
144
145 // Defer an invalidation of the options menu (on modern devices, the action bar). This
146 // can't be done immediately because the transaction may not yet be committed. Commits
147 // are asynchronous in that they are posted to the main thread's message loop.
148 mHandler.post(new Runnable() {
149 @Override
150 public void run() {
151 invalidateOptionsMenu();
152 }
153 });
154 }
155
156 @Override
157 public void onBackStackChanged() {
158 mShowingBack = (getFragmentManager().getBackStackEntryCount() > 0);
159
160 // When the back stack changes, invalidate the options menu (action bar).
161 invalidateOptionsMenu();
162 }
163
164 /**
165 * A fragment representing the front of the card.
166 */
167 public static class CardFrontFragment extends Fragment {
168 public CardFrontFragment() {
169 }
170
171 @Override
172 public View onCreateView(LayoutInflater inflater, ViewGroup container,
173 Bundle savedInstanceState) {
174 return inflater.inflate(R.layout.fragment_card_front, container, false);
175 }
176 }
177
178 /**
179 * A fragment representing the back of the card.
180 */
181 public static class CardBackFragment extends Fragment {
182 public CardBackFragment() {
183 }
184
185 @Override
186 public View onCreateView(LayoutInflater inflater, ViewGroup container,
187 Bundle savedInstanceState) {
188 return inflater.inflate(R.layout.fragment_card_back, container, false);
189 }
190 }
191 }
这段代码修改了Fragment从栈中保存和退出的动画，四个动画分别是：
1）card_flip_left_in.xml
1 <set xmlns:android="http://schemas.android.com/apk/res/android"> 2 <!-- Before rotating, immediately set the alpha to 0. --> 3 <objectAnimator 4 android:valueFrom="1.0" 5 android:valueTo="0.0" 6 android:propertyName="alpha" 7 android:duration="0" /> 8 9 <!-- Rotate. --> 10 <objectAnimator 11 android:valueFrom="-180" 12 android:valueTo="0" 13 android:propertyName="rotationY" 14 android:interpolator="@android:interpolator/accelerate_decelerate" 15 android:duration="@integer/card_flip_time_full" /> 16 17 <!-- Half-way through the rotation (see startOffset), set the alpha to 1. --> 18 <objectAnimator 19 android:valueFrom="0.0" 20 android:valueTo="1.0" 21 android:propertyName="alpha" 22 android:startOffset="@integer/card_flip_time_half" 23 android:duration="1" /> 24 </set>
2）card_flip_left_out.xml
1 <set xmlns:android="http://schemas.android.com/apk/res/android"> 2 <!-- Rotate. --> 3 <objectAnimator 4 android:valueFrom="0" 5 android:valueTo="180" 6 android:propertyName="rotationY" 7 android:interpolator="@android:interpolator/accelerate_decelerate" 8 android:duration="@integer/card_flip_time_full" /> 9 10 <!-- Half-way through the rotation (see startOffset), set the alpha to 0. --> 11 <objectAnimator 12 android:valueFrom="1.0" 13 android:valueTo="0.0" 14 android:propertyName="alpha" 15 android:startOffset="@integer/card_flip_time_half" 16 android:duration="1" /> 17 </set>
3）card_flip_right_in.xml
1 <set xmlns:android="http://schemas.android.com/apk/res/android"> 2 <!-- Before rotating, immediately set the alpha to 0. --> 3 <objectAnimator 4 android:valueFrom="1.0" 5 android:valueTo="0.0" 6 android:propertyName="alpha" 7 android:duration="0" /> 8 9 <!-- Rotate. --> 10 <objectAnimator 11 android:valueFrom="180" 12 android:valueTo="0" 13 android:propertyName="rotationY" 14 android:interpolator="@android:interpolator/accelerate_decelerate" 15 android:duration="@integer/card_flip_time_full" /> 16 17 <!-- Half-way through the rotation (see startOffset), set the alpha to 1. --> 18 <objectAnimator 19 android:valueFrom="0.0" 20 android:valueTo="1.0" 21 android:propertyName="alpha" 22 android:startOffset="@integer/card_flip_time_half" 23 android:duration="1" />
4）card_flip_right_out.xml
1 <set xmlns:android="http://schemas.android.com/apk/res/android"> 2 <!-- Rotate. --> 3 <objectAnimator 4 android:valueFrom="0" 5 android:valueTo="-180" 6 android:propertyName="rotationY" 7 android:interpolator="@android:interpolator/accelerate_decelerate" 8 android:duration="@integer/card_flip_time_full" /> 9 10 <!-- Half-way through the rotation (see startOffset), set the alpha to 0. --> 11 <objectAnimator 12 android:valueFrom="1.0" 13 android:valueTo="0.0" 14 android:propertyName="alpha" 15 android:startOffset="@integer/card_flip_time_half" 16 android:duration="1" /> 17 </set>
这边有个奇怪的ObjectAnimator，暂不讨论。
关键代码都在这里了，再加上两个View即可。其实很简单，就是修改了Fragment默认的切换动画，然后通过压栈和退栈实现了效果，不过可以仔细研究一下它的动画xml，比如通过设置duration=0来让某种属性（类似alpha）瞬间改变。
（详见：http://developer.android.com/training/animation/cardflip.html#views ）
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