SharedPreferences判断程序是否第一次运行

SharedPreferences是Android平台上一个轻量级的存储类，主要是保存一些常用的配置比如窗口状态，比如我们可以通过SharedPreferences来判断程序是不是第一次运行。

下面的实例将用于介绍怎样通过SharedPreferences来判断程序是否是第一次运行，其实现思路很简单，通过在SharedPreferences中存储键值表示程序是否第一次运行。代码如下：

<span style="color:#33CC00;">public class PreferenceTestMain extends Activity {        public static final String PREFS_NAME = "MyPrefsFile";        public static final String FIRST_RUN = "first";        private boolean first;        /** Called when the activity is first created. */        @Override        public void onCreate(Bundle savedInstanceState) {                super.onCreate(savedInstanceState);                setContentView(R.layout.main);                // Restore preferences                SharedPreferences settings = getSharedPreferences(PREFS_NAME, 0);                first = settings.getBoolean(FIRST_RUN, true);                if (first) {                        Toast.makeText(this, "The Application is first run",                                        Toast.LENGTH_LONG).show();                } else {                        Toast.makeText(this, "The Application is not first run",                                        Toast.LENGTH_LONG).show();                }        }        @Override        protected void onStop() {                super.onStop();                // We need an Editor object to make preference changes.                // All objects are from android.context.Context                SharedPreferences settings = getSharedPreferences(PREFS_NAME, 0);                SharedPreferences.Editor editor = settings.edit();                if (first) {                        editor.putBoolean(FIRST_RUN, false);                }                // Commit the edits!                editor.commit();        }}</span>

其中在 onCreate 方法中读取，SharedPreferences 信息，在 onStop 中保存 SharedPreferences信息。注意程序的状态信息一般都在 onStop 保存。