如何在Android中管理音频焦点？

Android中的音频焦点需要管理，这是处理音频中断的重要方法之一。在android中，许多应用程序同时播放媒体，并且为了增加用户体验，音频中断得到处理。例如，如果应用程序正在播放音频，则突然有一个来话呼叫，则需要停止音频文件，并且在通话结束后，音频应从停止处继续播放。本文讨论了如何处理音频中断或如何在Android中实现音频焦点。请看以下图片，以了解将要讨论的内容。注意，我们将使用Java语言实现该项目。

实施音频焦点或处理音频中断的步骤

步骤1：创建一个空的活动项目

• 创建一个空的活动Android Studio项目。并选择Java作为编程语言。
• 要了解如何创建一个空的活动Android Studio项目，请参阅Android |如何在Android Studio中创建/启动新项目?

步骤2：使用activity_main.xml文件

• 该项目的主要布局仅包含三个按钮，这些按钮用于播放，暂停和停止在应用程序中播放音频文件。
• 调用以下代码以实现UI。

输出界面：

步骤3：使用MainActivity。 Java文件

• 当音频焦点发生变化时，需要实现主要的回调。意味着系统已将音频焦点转移到该应用程序使用的另一服务，在这种情况下，是Phone应用程序，该应用程序从正在播放音频的当前应用程序获取音频焦点。

AudioManager.OnAudioFocusChangeListener audioFocusChangeListener -> This handles if there is change in the audio focus which the callback need to implemented according to the focus change from the audio manage.

• 挂断电话后，焦点将更改为当前应用程序，并恢复MediaPlayer。
• 将Android系统返回的焦点请求结果与以下常量进行比较。

1. AUDIOFOCUS_GAIN: if the system grants the audio focus gain, then the playback can be continued after the temporary loss of the audio focus.
2. AUDIOFOCUS_LOSS_TRANSIENT: if there is temporary loss of audio focus then the playback of the audio should be paused.
3. AUDIOFOCUS_LOSS: if there is permenant loss of the audio then the mediaplayer should be released (completely stopped).

• 要在与上述相同的应用程序中实现音频焦点，请在MainActivity中调用以下代码。 Java文件。添加了注释以便更好地理解。

Java

import androidx.annotation.RequiresApi;
import androidx.appcompat.app.AppCompatActivity;
import android.content.Context;
import android.media.AudioAttributes;
import android.media.AudioFocusRequest;
import android.media.AudioManager;
import android.media.MediaPlayer;
import android.os.Build;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import java.io.IOException;
  
@RequiresApi(api = Build.VERSION_CODES.O)
public class MainActivity extends AppCompatActivity {
  
    // media player instance to playback 
      // the media file from the raw folder
    MediaPlayer mediaPlayer;
  
    // Audio manager instance to manage or 
      // handle the audio interruptions
    AudioManager audioManager;
  
    // Audio attributes instance to set the playback 
      // attributes for the media player instance
    // these attributes specify what type of media is 
      // to be played and used to callback the audioFocusChangeListener
    AudioAttributes playbackAttributes;
  
    // media player is handled according to the 
      // change in the focus which Android system grants for
    AudioManager.OnAudioFocusChangeListener audioFocusChangeListener = new AudioManager.OnAudioFocusChangeListener() {
        @Override
        public void onAudioFocusChange(int focusChange) {
            if (focusChange == AudioManager.AUDIOFOCUS_GAIN) {
                mediaPlayer.start();
            } else if (focusChange == AudioManager.AUDIOFOCUS_LOSS_TRANSIENT) {
                mediaPlayer.pause();
                mediaPlayer.seekTo(0);
            } else if (focusChange == AudioManager.AUDIOFOCUS_LOSS) {
                mediaPlayer.release();
            }
        }
    };
  
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
  
        // get the audio system service for 
          // the audioManger instance
        audioManager = (AudioManager) getSystemService(Context.AUDIO_SERVICE);
  
        // initiate the audio playback attributes
        playbackAttributes = new AudioAttributes.Builder()
                .setUsage(AudioAttributes.USAGE_GAME)
                .setContentType(AudioAttributes.CONTENT_TYPE_MUSIC)
                .build();
  
        // set the playback attributes for the focus requester
        AudioFocusRequest focusRequest = new AudioFocusRequest.Builder(AudioManager.AUDIOFOCUS_GAIN)
                .setAudioAttributes(playbackAttributes)
                .setAcceptsDelayedFocusGain(true)
                .setOnAudioFocusChangeListener(audioFocusChangeListener)
                .build();
  
        // request the audio focus and
          // store it in the int variable
        final int audioFocusRequest = audioManager.requestAudioFocus(focusRequest);
  
        // register all three buttons
        Button bPlay = findViewById(R.id.playButton);
        Button bPause = findViewById(R.id.pasueButton);
        Button bStop = findViewById(R.id.stopButton);
  
        // initiate the media player instance with
          // the media file from the raw folder
        mediaPlayer = MediaPlayer.create(getApplicationContext(), R.raw.music);
  
        // handle the PLAY button to play the audio
        bPlay.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                // request the audio focus by the Android system
                  // if the system grants the permission
                // then start playing the audio file
                if (audioFocusRequest == AudioManager.AUDIOFOCUS_REQUEST_GRANTED) {
                    mediaPlayer.start();
                }
            }
        });
  
        // handle the PAUSE button to pause the media player
        bPause.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                mediaPlayer.pause();
            }
        });
  
        // handle the STOP button to stop the media player
        bStop.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                mediaPlayer.stop();
  
                try {
                    // if the mediaplayer is stopped then
                      // it should be again prepared for
                    // next instance of play
                    mediaPlayer.prepare();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        });
  
    }
}

Note: When there is no requirement of audio focus, abandonAudioFocusRequest method needs to be called with the AudioManager instance and it requires the parameter AudioFocusRequest focusRequest which needs to be passed.

输出：在模拟器上运行

想要一个节奏更快，更具竞争性的环境来学习Android的基础知识吗?

单击此处，前往由我们的专家精心策划的指南，以使您立即做好行业准备！