学步园

本文翻译自《50 android hacks》

默认情况下，ViewGroup中的子视图是直接显示出来的。有一个简单的方法可以为这个过程添加动画效果。

主要使用LayoutAnimationController类，有一点需要注意，不可以为每一个单独的子视图分别指定不同的动画效果。

下面是在ListView中为每一个Item添加动画效果的例子。

主文件，代码如下：

public class MainActivity extends ListActivity {

  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    getListView().setLayoutAnimation(
        new LayoutAnimationController(AnimationUtils.loadAnimation(
            this, R.anim.list_animation), 0.5f));

    setListAdapter(new ArrayAdapter<String>(this,
        android.R.layout.simple_list_item_1, Countries.COUNTRIES));
  }
}

首先获取ListView的实例，然后调用setLayoutAnimation()方法，传入LayoutAnimationController对象。

动画文件，代码如下：

<set xmlns:android="http://schemas.android.com/apk/res/android" >

    <alpha
        android:duration="50"
        android:fromAlpha="0"
        android:toAlpha="1" />

    <translate
        android:duration="100"
        android:fromYDelta="-100%"
        android:toYDelta="0%" />

</set>

同时显示alpha和translate动画。

Countries.java文件，即ListView的数据源。代码如下：

public class Countries {
  public static final String[] COUNTRIES = new String[] {
      "Afghanistan", "Albania", "Algeria", "American Samoa", "Andorra",
      "Angola", "Anguilla", "Antarctica", "Antigua and Barbuda",
      "Argentina", "Armenia", "Aruba", "Australia", "Austria",
      "Azerbaijan", "Bahrain", "Bangladesh", "Barbados", "Belarus",
      "Belgium", "Belize", "Benin", "Bermuda", "Bhutan", "Bolivia",
      "Bosnia and Herzegovina", "Botswana", "Bouvet Island", "Brazil",
      "British Indian Ocean Territory", "British Virgin Islands",
      "Brunei", "Bulgaria", "Burkina Faso", "Burundi", "Cote d'Ivoire",
      "Cambodia", "Cameroon", "Canada", "Cape Verde", "Cayman Islands",
      "Central African Republic", "Chad", "Chile", "China",
      "Christmas Island", "Cocos (Keeling) Islands", "Colombia",
      "Comoros", "Congo", "Cook Islands", "Costa Rica", "Croatia",
      "Cuba", "Cyprus", "Czech Republic",
      "Democratic Republic of the Congo", "Denmark", "Djibouti",
      "Dominica", "Dominican Republic", "East Timor", "Ecuador",
      "Egypt", "El Salvador", "Equatorial Guinea", "Eritrea",
      "Estonia", "Ethiopia", "Faeroe Islands", "Falkland Islands",
      "Fiji", "Finland", "Former Yugoslav Republic of Macedonia",
      "France", "French Guiana", "French Polynesia",
      "French Southern Territories", "Gabon", "Georgia", "Germany",
      "Ghana", "Gibraltar", "Greece", "Greenland", "Grenada",
      "Guadeloupe", "Guam", "Guatemala", "Guinea", "Guinea-Bissau",
      "Guyana", "Haiti", "Heard Island and McDonald Islands",
      "Honduras", "Hong Kong", "Hungary", "Iceland", "India",
      "Indonesia", "Iran", "Iraq", "Ireland", "Israel", "Italy",
      "Jamaica", "Japan", "Jordan", "Kazakhstan", "Kenya", "Kiribati",
      "Kuwait", "Kyrgyzstan", "Laos", "Latvia", "Lebanon", "Lesotho",
      "Liberia", "Libya", "Liechtenstein", "Lithuania", "Luxembourg",
      "Macau", "Madagascar", "Malawi", "Malaysia", "Maldives", "Mali",
      "Malta", "Marshall Islands", "Martinique", "Mauritania",
      "Mauritius", "Mayotte", "Mexico", "Micronesia", "Moldova",
      "Monaco", "Mongolia", "Montserrat", "Morocco", "Mozambique",
      "Myanmar", "Namibia", "Nauru", "Nepal", "Netherlands",
      "Netherlands Antilles", "New Caledonia", "New Zealand",
      "Nicaragua", "Niger", "Nigeria", "Niue", "Norfolk Island",
      "North Korea", "Northern Marianas", "Norway", "Oman", "Pakistan",
      "Palau", "Panama", "Papua New Guinea", "Paraguay", "Peru",
      "Philippines", "Pitcairn Islands", "Poland", "Portugal",
      "Puerto Rico", "Qatar", "Reunion", "Romania", "Russia", "Rwanda",
      "Sqo Tome and Principe", "Saint Helena", "Saint Kitts and Nevis",
      "Saint Lucia", "Saint Pierre and Miquelon",
      "Saint Vincent and the Grenadines", "Samoa", "San Marino",
      "Saudi Arabia", "Senegal", "Seychelles", "Sierra Leone",
      "Singapore", "Slovakia", "Slovenia", "Solomon Islands",
      "Somalia", "South Africa",
      "South Georgia and the South Sandwich Islands", "South Korea",
      "Spain", "Sri Lanka", "Sudan", "Suriname",
      "Svalbard and Jan Mayen", "Swaziland", "Sweden", "Switzerland",
      "Syria", "Taiwan", "Tajikistan", "Tanzania", "Thailand",
      "The Bahamas", "The Gambia", "Togo", "Tokelau", "Tonga",
      "Trinidad and Tobago", "Tunisia", "Turkey", "Turkmenistan",
      "Turks and Caicos Islands", "Tuvalu", "Virgin Islands", "Uganda",
      "Ukraine", "United Arab Emirates", "United Kingdom",
      "United States", "United States Minor Outlying Islands",
      "Uruguay", "Uzbekistan", "Vanuatu", "Vatican City", "Venezuela",
      "Vietnam", "Wallis and Futuna", "Western Sahara", "Yemen",
      "Yugoslavia", "Zambia", "Zimbabwe" };
}

参考资料

http://developer.android.com/reference/android/view/animation/LayoutAnimationController.html