添加后台监听按键的方法

AndroidManifest.xml

@@ -22,6 +22,15 @@
                 <category android:name="android.intent.category.LAUNCHER" />
             </intent-filter>
         </activity>
+        <receiver android:name=".MusicIntentReceiver">
+            <intent-filter>
+                <action android:name="android.media.AUDIO_BECOMING_NOISY" />
+            </intent-filter>
+            <intent-filter>
+                <action android:name="android.intent.action.MEDIA_BUTTON" />
+            </intent-filter>
+        </receiver>
+
     </application>
 
 </manifest>

src/com/example/testkey/MainActivity.java

@@ -2,9 +2,11 @@
 
 import android.app.Activity;
 import android.content.BroadcastReceiver;
+import android.content.ComponentName;
 import android.content.Context;
 import android.content.Intent;
 import android.content.IntentFilter;
+import android.media.AudioManager;
 import android.media.MediaPlayer;
 import android.media.MediaPlayer.OnPreparedListener;
 import android.os.Bundle;
@@ -54,6 +56,11 @@ public void onCheckedChanged(CompoundButton buttonView,
                 update();
             }
         });
+
+        // for service
+        ((AudioManager)getSystemService(AUDIO_SERVICE)).registerMediaButtonEventReceiver(new ComponentName(
+                this,
+                MusicIntentReceiver.class));
     }
 
 
@@ -212,6 +219,7 @@ public boolean onKeyDown(int keyCode, KeyEvent event) {
 
     public void printToast(String str) {
         tv.setText(str);
+        Log.i(LOG_TAG, str);
     }
 
     private final BroadcastReceiver homePressReceiver = new BroadcastReceiver() {

src/com/example/testkey/MusicIntentReceiver.java

@@ -0,0 +1,72 @@
+/*   
+ * Copyright (C) 2011 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.example.testkey;
+
+import android.content.BroadcastReceiver;
+import android.content.Context;
+import android.content.Intent;
+import android.util.Log;
+import android.view.KeyEvent;
+import android.widget.Toast;
+
+/**
+ * Receives broadcasted intents. In particular, we are interested in the
+ * android.media.AUDIO_BECOMING_NOISY and android.intent.action.MEDIA_BUTTON intents, which is
+ * broadcast, for example, when the user disconnects the headphones. This class works because we are
+ * declaring it in a <receiver> tag in AndroidManifest.xml.
+ */
+public class MusicIntentReceiver extends BroadcastReceiver {
+    @Override
+    public void onReceive(Context context, Intent intent) {
+        if (intent.getAction().equals(android.media.AudioManager.ACTION_AUDIO_BECOMING_NOISY)) {
+            Toast.makeText(context, "Headphones disconnected.", Toast.LENGTH_SHORT).show();
+
+            // send an intent to our MusicService to telling it to pause the audio
+            //context.startService(new Intent(MusicService.ACTION_PAUSE));
+
+        } else if (intent.getAction().equals(Intent.ACTION_MEDIA_BUTTON)) {
+            Log.i("MusicIntentReceiver", "ACTION_MEDIA_BUTTON!");
+            KeyEvent keyEvent = (KeyEvent) intent.getExtras().get(Intent.EXTRA_KEY_EVENT);
+            if (keyEvent.getAction() != KeyEvent.ACTION_DOWN)
+                return;
+
+            switch (keyEvent.getKeyCode()) {
+                case KeyEvent.KEYCODE_HEADSETHOOK:
+                case KeyEvent.KEYCODE_MEDIA_PLAY_PAUSE:
+                    //context.startService(new Intent(MusicService.ACTION_TOGGLE_PLAYBACK));
+                    break;
+                case KeyEvent.KEYCODE_MEDIA_PLAY:
+                    //context.startService(new Intent(MusicService.ACTION_PLAY));
+                    break;
+                case KeyEvent.KEYCODE_MEDIA_PAUSE:
+                    //context.startService(new Intent(MusicService.ACTION_PAUSE));
+                    break;
+                case KeyEvent.KEYCODE_MEDIA_STOP:
+                    //context.startService(new Intent(MusicService.ACTION_STOP));
+                    break;
+                case KeyEvent.KEYCODE_MEDIA_NEXT:
+                    //context.startService(new Intent(MusicService.ACTION_SKIP));
+                    break;
+                case KeyEvent.KEYCODE_MEDIA_PREVIOUS:
+                    // TODO: ensure that doing this in rapid succession actually plays the
+                    // previous song
+                    //context.startService(new Intent(MusicService.ACTION_REWIND));
+                    break;
+            }
+        }
+    }
+}