AlarmAlertActivity 精读

src/net/micode/notes/ui/AlarmAlertActivity.java

@@ -43,8 +43,8 @@ import java.io.IOException;
 public class AlarmAlertActivity extends Activity implements OnClickListener, OnDismissListener {
     private long mNoteId;     //文本在数据存储中的ID号
     private String mSnippet;   //闹钟提示时出现的文本片段
-    private static final int SNIPPET_PREW_MAX_LEN = 60;
-    MediaPlayer mPlayer;
+    private static final int SNIPPET_PREW_MAX_LEN = 60; //闹钟提示对话框中的便签片段的最大长度
+    MediaPlayer mPlayer; //用于播放闹钟音效的MediaPlayer对象
 
     @Override
     protected void onCreate(Bundle savedInstanceState) {
@@ -52,9 +52,10 @@ public class AlarmAlertActivity extends Activity implements OnClickListener, OnD
         //Bundle 类型的数据与 Map类型的数据相似，都是以keu-value的形式存储数据的
         //on save InstanceState方法是用来保存Activity的状态的
         //能从onCreate的参数savedInsanceState中获得状态数据
+        //不显示窗口标题
         requestWindowFeature(Window.FEATURE_NO_TITLE);
-        //界面显示-无标题
 
+        //获取当前窗口的Window实例，用于设置标志以在屏幕锁定时显示此Activity
         final Window win = getWindow();
         win.addFlags(WindowManager.LayoutParams.FLAG_SHOW_WHEN_LOCKED);
 
@@ -70,6 +71,7 @@ public class AlarmAlertActivity extends Activity implements OnClickListener, OnD
 
         Intent intent = getIntent();
 
+        //从Intent的data中提取闹钟ID(mNoteId)和文本片段(mSnippet)
         try {
             mNoteId = Long.valueOf(intent.getData().getPathSegments().get(1));
             mSnippet = DataUtils.getSnippetById(this.getContentResolver(), mNoteId);
@@ -80,6 +82,7 @@ public class AlarmAlertActivity extends Activity implements OnClickListener, OnD
                     : mSnippet;
             //判读标签片段是否达到符合长度
         } catch (IllegalArgumentException e) {
+            //数据不合法，捕获异常并返回
             e.printStackTrace();
             return;
         }
@@ -105,22 +108,28 @@ public class AlarmAlertActivity extends Activity implements OnClickListener, OnD
         }
     }
 
+    //判断屏幕是否亮起
     private boolean isScreenOn() {
         PowerManager pm = (PowerManager) getSystemService(Context.POWER_SERVICE);
         return pm.isScreenOn();
     }
 
+    //播放默认的闹钟声音
     private void playAlarmSound() {
+        //获取系统默认的闹钟声音URI
         Uri url = RingtoneManager.getActualDefaultRingtoneUri(this, RingtoneManager.TYPE_ALARM);
 
+        //获取当前系统设置的闹钟流是否受静音模式影响
         int silentModeStreams = Settings.System.getInt(getContentResolver(),
                 Settings.System.MODE_RINGER_STREAMS_AFFECTED, 0);
 
+        //如果闹钟声音在当前系统设置中受静音模式影响，则将其设置到相应的音频流
         if ((silentModeStreams & (1 << AudioManager.STREAM_ALARM)) != 0) {
             mPlayer.setAudioStreamType(silentModeStreams);
         } else {
             mPlayer.setAudioStreamType(AudioManager.STREAM_ALARM);
         }
+        //尝试设置数据源，准备播放器，设置为循环播放，并开始播放
         try {
             mPlayer.setDataSource(this, url);
             mPlayer.prepare();
@@ -137,22 +146,28 @@ public class AlarmAlertActivity extends Activity implements OnClickListener, OnD
             e.printStackTrace();
         } catch (IOException e) {
             // TODO Auto-generated catch block
-            e.printStackTrace();
+            e.printStackTrace(); //捕捉到异常，输出堆栈跟踪信息并不做进一步处理
         }
     }
 
+    //显示操作对话框，让用户能够选择停止闹钟或查看便签
     private void showActionDialog() {
         AlertDialog.Builder dialog = new AlertDialog.Builder(this);
+        //设置对话框标题和消息，并提供一个"确定"按钮
         dialog.setTitle(R.string.app_name);
         dialog.setMessage(mSnippet);
         dialog.setPositiveButton(R.string.notealert_ok, this);
+        //如果屏幕已经亮起，则提供一个"查看"按钮
         if (isScreenOn()) {
             dialog.setNegativeButton(R.string.notealert_enter, this);
         }
+        //显示对话框，并设置监听器监听对话框消失事件
         dialog.show().setOnDismissListener(this);
     }
 
+    //当用户点击对话框按钮时调用这个方法
     public void onClick(DialogInterface dialog, int which) {
+        //如果点击了"查看"按钮，启动NoteEditActivity来查看并编辑便签
         switch (which) {
             case DialogInterface.BUTTON_NEGATIVE:
                 Intent intent = new Intent(this, NoteEditActivity.class);
@@ -165,11 +180,13 @@ public class AlarmAlertActivity extends Activity implements OnClickListener, OnD
         }
     }
 
+    //当对话框消失时，停止播放声音并结束此活动
     public void onDismiss(DialogInterface dialog) {
         stopAlarmSound();
         finish();
     }
 
+    //停止并释放MediaPlayer资源
     private void stopAlarmSound() {
         if (mPlayer != null) {
             mPlayer.stop();