Audio音乐播放器编写 及 MediaPlayer 实例化代码分析
六、Audio音乐播放器编写
6.1 音乐播放器APK编写
6.1.1 APK 界面 xml 文件代码
- activity_main.xml 文件内容
<!-- @\MusicDeamon\app\src\main\res\layout\activity_main.xml -->
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context=".MainActivity">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="55dp"
android:layout_weight="1">
<TextView
android:id="@+id/textView3"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_weight="1"
android:text="Text Reserve ..." />
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="298dp"
android:layout_weight="7"
android:orientation="vertical">
<ListView
android:id="@+id/list_view"
android:layout_width="match_parent"
android:layout_height="271dp"
android:layout_weight="1"
tools:layout_editor_absoluteX="16dp"
tools:layout_editor_absoluteY="46dp" />
<SeekBar
android:id="@+id/seekBar"
android:layout_width="match_parent"
android:layout_height="56dp" />
<TextView
android:id="@+id/MusicName"
android:layout_width="match_parent"
android:layout_height="44dp"
android:text="Text Reserve ..." />
<LinearLayout
android:layout_width="match_parent"
android:layout_height="67dp"
android:layout_gravity="top"
android:layout_weight="10">
<Button
android:id="@+id/btn_pre"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:onClick="btn_pre_click"
android:text="上一曲" />
<Button
android:id="@+id/btn_start"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:onClick="btn_start_click"
android:text="开始/暂停" />
<Button
android:id="@+id/btn_next"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:onClick="btn_next_click"
android:text="下一曲" />
<Button
android:id="@+id/btn_stop"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:onClick="btn_stop_click"
android:text="停止" />
</LinearLayout>
</LinearLayout>
</LinearLayout>
- item.xml 文件内容
<!-- @ \MusicDeamon\app\src\main\res\layout\item.xml -->
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:id="@+id/mName"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="aaaa"
android:textSize="20sp"
/>
</LinearLayout>
6.1.2 APK Java 文件代码
// @ \MusicDeamon\app\src\main\java\com\jaimex\musicdeamon\MainActivity.java
package com.jaimex.musicdeamon;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.media.MediaPlayer;
import android.os.Bundle;
import android.os.Environment;
import android.os.Handler;
import android.telephony.PhoneStateListener;
import android.telephony.TelephonyManager;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.Button;
import android.widget.ListView;
import android.widget.SeekBar;
import android.widget.SimpleAdapter;
import android.widget.TextView;
import androidx.appcompat.app.AppCompatActivity;
import java.io.File;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
public class MainActivity extends AppCompatActivity {
private final static String TAG="MusicDaemon";
private TextView MusicNameTextView;
private SeekBar seekBar;
private ListView listView;
private List<Map<String, String>> data;
private int current;
private MediaPlayer player;
private Handler handler = new Handler();
private Button btn_next;
private Button btn_pre;
private Button btn_start;
private Button btn_stop;
private boolean isPause;
private boolean isStartTrackingTouch;
private Object file;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// 找到控件
MusicNameTextView = (TextView) findViewById(R.id.MusicName);
seekBar = (SeekBar) findViewById(R.id.seekBar);
listView = (ListView) findViewById(R.id.list_view);
btn_next = (Button) findViewById(R.id.btn_next);
btn_pre = (Button) findViewById(R.id.btn_pre);
btn_start = (Button) findViewById(R.id.btn_start);
btn_stop = (Button) findViewById(R.id.btn_stop);
//1. 创建一个音乐播放器
player = new MediaPlayer();
//2. 显示音乐播放列表
generateListView();
//3. 进度条监听器
seekBar.setOnSeekBarChangeListener(new MySeekBarListener());
//4. 实例化MyPlayerListener， 监听播放器是否播放完毕，如果播放完毕，则自动播放下一首
player.setOnCompletionListener(new MyPlayerListener());
Log.i(TAG, "onCreate: end");
}
///////////////////////////////////////////////////////////
/* 前一首按钮 */
public void btn_pre_click(View view) {
Log.i(TAG, "btn_pre_click: ");
previous();
}
/* 下一首按钮 */
public void btn_next_click(View view) {
Log.i(TAG, "btn_next_click: ");
next();
}
/* 暂停/播放按钮 */
public void btn_start_click(View view) {
Log.i(TAG, "btn_start_click: ");
//默认从第一首歌曲开始播放
if (!player.isPlaying() && !isPause) {
play();
return;
}
Button button = (Button) view;
//暂停/播放按钮
if ("||".equals(button.getText())) {
pause();
button.setText("▶");
} else {
resume();
button.setText("||");
}
}
/* 停止播放 */
public void btn_stop_click(View view) {
Log.i(TAG, "btn_stop_click: ");
if (player != null && player.isPlaying()) {
player.stop();
player.reset();
}
}
///////////////////////////////////////////////////////////
/* 播放器监听器*/
private final class MyPlayerListener implements MediaPlayer.OnCompletionListener {
//歌曲播放完后自动播放下一首歌曲
public void onCompletion(MediaPlayer mp) {
Log.i(TAG, "onCompletion: ");
next();
}
}
/* 播放前一首歌 */
private void previous() {
current = current - 1 < 0 ? data.size() - 1 : current - 1;
Log.i(TAG, "previous: " + "current=" + current);
play();
}
/* 播放下一首歌 */
private void next() {
current = (current + 1) % data.size();
Log.i(TAG, "next: " + "current=" + current);
play();
}
/*
* 进度条监听器
*/
private final class MySeekBarListener implements SeekBar.OnSeekBarChangeListener {
//移动触发
public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
Log.i(TAG, "onProgressChanged: ");
}
//起始触发
public void onStartTrackingTouch(SeekBar seekBar) {
isStartTrackingTouch = true;
Log.i(TAG, "onStartTrackingTouch: " + isStartTrackingTouch);
}
//结束触发
public void onStopTrackingTouch(SeekBar seekBar) {
player.seekTo(seekBar.getProgress());
isStartTrackingTouch = false;
Log.i(TAG, "onStartTrackingTouch: " + isStartTrackingTouch);
}
}
/*
* 显示音乐播放列表
*/
private void generateListView() {
List<File> list = new ArrayList<File>();
//获取sdcard中的所有歌曲
findAll(Environment.getExternalStorageDirectory(), list);
//for(File f : list)
// Log.i(TAG, "generateListView: " + " list name=" + f.getName());
//播放列表进行排序，字符顺序
Collections.sort(list);
data = new ArrayList<Map<String, String>>();
for (File file : list) {
Map<String, String> map = new HashMap<String, String>();
map.put("name", file.getName());
map.put("path", file.getAbsolutePath());
Log.i(TAG, "generateListView: "+" name="+file.getName() + " path="+file.getAbsolutePath());
data.add(map);
}
SimpleAdapter adapter = new SimpleAdapter(this, data, R.layout.item, new String[] { "path" }, new int[] { R.id.mName });
listView.setAdapter(adapter);
listView.setOnItemClickListener(new MyItemListener());
}
private final class MyItemListener implements AdapterView.OnItemClickListener {
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
current = position;
Log.i(TAG, "onItemClick: "+ "current=" + current);
play();
}
}
private void play() {
Log.i(TAG, "play: "+"+++");
try {
//重播
player.reset();
//获取歌曲路径
player.setDataSource(data.get(current).get("path"));
//缓冲
player.prepare();
//开始播放
player.start();
//显示歌名
MusicNameTextView.setText("当前播放歌曲： " + data.get(current).get("name"));
//设置进度条长度
seekBar.setMax(player.getDuration());
//播放按钮样式
btn_start.setText("||");
//发送一个Runnable, handler收到之后就会执行run()方法
handler.post(new Runnable() {
public void run() {
// 更新进度条状态
if (!isStartTrackingTouch)
seekBar.setProgress(player.getCurrentPosition());
// 1秒之后再次发送
handler.postDelayed(this, 1000);
}
});
} catch (Exception e) {
Log.i(TAG, "play: "+" error !!!");
e.printStackTrace();
}
Log.i(TAG, "play: "+"---");
}
/**
* 查找文件路径中所有mp3文件
* @param file 要找的目录
* @param list 用来装文件的List
*/
private void findAll(File file, List<File> list) {
//Log.i(TAG, "findAll: " + " file path=" + file.getAbsolutePath() );
File[] subFiles = file.listFiles();
if (subFiles != null){
for (File subFile : subFiles) {
//Log.i(TAG, "findAll: "+ " file name =" + subFile.getName());
if (subFile.isFile() && subFile.getName().endsWith(".mp3")) {
list.add(subFile);
Log.i(TAG, "findAll: "+ " file name =" + subFile.getName());
}else if (subFile.isDirectory())//如果是目录
findAll(subFile, list); //递归
}
}
}
/* 开始操作 */
private void resume() {
if (isPause) {
player.start();
isPause = false;
}
Log.i(TAG, "resume: "+isPause);
}
/* 暂停操作 */
private void pause() {
if (player != null && player.isPlaying()) {
player.pause();
isPause = true;
Log.i(TAG, "pause: "+isPause);
}
}
/* 收到广播时暂停 */
private final class PhoneListener extends BroadcastReceiver {
public void onReceive(Context context, Intent intent) {
Log.i(TAG, "onReceive: ");
pause();
}
}
/* 恢复播放 */
protected void onResume() {
super.onResume();
Log.i(TAG, "onResume: ");
//resume();
}
}
6.1.3 APK 实测结果
在安卓模拟器上实测，正常，界面比较简漏
6.2 MediaPlay 播放流程代码分析
简化前面 apk java 的代码，可以知道要使用 MediaPlay 播放一首歌的话，
主要代码如下：
开始播放流程 ：
player = new MediaPlayer(); //1. 创建一个音乐播放器
//设置歌曲播放路径
player.setDataSource(data.get(current).get("path"));
//缓冲
player.prepare();
//开始播放
player.start();
接下来，我们依次分析下前面的代码流程
6.2.1 MediaPlayer 实例化代码分析
player = new MediaPlayer();
在MediaPlayer 代码中，首先会加 libmedia_jni.so 库文件，接着调用 native_init() 初始化 Native 层JNI 方法。
native_init 主要流程如下：
- 在Native 层中找到Java 中MediaPlayer Class 的对象，通过该对象可找到中的 Java 方法
- 获得 MediaPlayer.java 中 postEventFromNative() 方法供回调使用
- 获得 MediaPlayer.java 中 mNativeSurfaceTexture 变量
@ \frameworks\base\media\java\android\media\MediaPlayer.java
static {
System.loadLibrary("media_jni");
native_init();
}
--------------------------------------------------------------------------------
native_init方法定义如下
@ \frameworks\base\media\jni\android_media_MediaPlayer.cpp
{"native_init", "()V", (void *)android_media_MediaPlayer_native_init},
------->
// This function gets some field IDs, which in turn causes class initialization.
// It is called from a static block in MediaPlayer, which won't run until the
// first time an instance of this class is used.
static void android_media_MediaPlayer_native_init(JNIEnv *env)
{
jclass clazz;
// 1. 在Native 层中找到Java 中MediaPlayer Class 的对象，通过该对象可找到中的 Java 方法
clazz = env->FindClass("android/media/MediaPlayer");
fields.context = env->GetFieldID(clazz, "mNativeContext", "J");
// 2. 获得 MediaPlayer.java 中 postEventFromNative() 方法供回调使用
fields.post_event = env->GetStaticMethodID(clazz, "postEventFromNative","(Ljava/lang/Object;IIILjava/lang/Object;)V");
// 3. 获得 MediaPlayer.java 中 mNativeSurfaceTexture 变量
fields.surface_texture = env->GetFieldID(clazz, "mNativeSurfaceTexture", "J");
env->DeleteLocalRef(clazz); // 清空 clazz 局部变量
clazz = env->FindClass("android/net/ProxyInfo");
fields.proxyConfigGetHost = env->GetMethodID(clazz, "getHost", "()Ljava/lang/String;");
fields.proxyConfigGetPort = env->GetMethodID(clazz, "getPort", "()I");
fields.proxyConfigGetExclusionList = env->GetMethodID(clazz, "getExclusionListAsString", "()Ljava/lang/String;");
env->DeleteLocalRef(clazz);
gBufferingParamsFields.init(env);
// Modular DRM
FIND_CLASS(clazz, "android/media/MediaDrm$MediaDrmStateException");
if (clazz) {
GET_METHOD_ID(gStateExceptionFields.init, clazz, "<init>", "(ILjava/lang/String;)V");
gStateExceptionFields.classId = static_cast<jclass>(env->NewGlobalRef(clazz));
env->DeleteLocalRef(clazz);
} else {
ALOGE("JNI android_media_MediaPlayer_native_init couldn't get clazz android/media/MediaDrm$MediaDrmStateException");
}
gPlaybackParamsFields.init(env);
gSyncParamsFields.init(env);
gVolumeShaperFields.init(env);
}
在构造函数中：
@ \frameworks\base\media\java\android\media\MediaPlayer.java
public class MediaPlayer extends PlayerBase implements SubtitleController.Listener, VolumeAutomation
{
public MediaPlayer() {
super(new AudioAttributes.Builder().build(), AudioPlaybackConfiguration.PLAYER_TYPE_JAM_MEDIAPLAYER);
Looper looper;
// 如果调用MediaPlayer构造方法的线程有自己的looper，就用子线程的looper，否则使用主线程的looper
if ((looper = Looper.myLooper()) != null) {
mEventHandler = new EventHandler(this, looper);
} else if ((looper = Looper.getMainLooper()) != null) {
mEventHandler = new EventHandler(this, looper);
} else {
mEventHandler = null;
}
mTimeProvider = new TimeProvider(this);
mOpenSubtitleSources = new Vector<InputStream>();
/* Native setup requires a weak reference to our object.
* It's easier to create it here than in C++.
*/
native_setup(new WeakReference<MediaPlayer>(this));
baseRegisterPlayer();
}
}
--------------------------------------------------------------------------------
native_setup 方法定义如下
@ \frameworks\base\media\jni\android_media_MediaPlayer.cpp
{"native_setup", "(Ljava/lang/Object;)V", (void *)android_media_MediaPlayer_native_setup},
---------->
static void android_media_MediaPlayer_native_setup(JNIEnv *env, jobject thiz, jobject weak_this)
{
ALOGV("native_setup");
sp<MediaPlayer> mp = new MediaPlayer(); //创建native的MediaPlayer对象
//为native的对象设置监听
// create new listener and give it to MediaPlayer
sp<JNIMediaPlayerListener> listener = new JNIMediaPlayerListener(env, thiz, weak_this);
mp->setListener(listener);
//将native对象的保存到Java对象的成员mNativeContext中
// Stow our new C++ MediaPlayer in an opaque field in the Java object.
setMediaPlayer(env, thiz, mp);
}
--------------------------------------------------------------------------------
@ \frameworks\base\media\java\android\media\PlayerBase.java
protected void baseRegisterPlayer() {
int newPiid = AudioPlaybackConfiguration.PLAYER_PIID_INVALID;
IBinder b = ServiceManager.getService(Context.APP_OPS_SERVICE);
mAppOps = IAppOpsService.Stub.asInterface(b);
// initialize mHasAppOpsPlayAudio
updateAppOpsPlayAudio();
// register a callback to monitor whether the OP_PLAY_AUDIO is still allowed
mAppOpsCallback = new IAppOpsCallbackWrapper(this);
try {
mAppOps.startWatchingMode(AppOpsManager.OP_PLAY_AUDIO,
ActivityThread.currentPackageName(), mAppOpsCallback);
} catch (RemoteException e) {
mHasAppOpsPlayAudio = false;
}
try {
newPiid = getService().trackPlayer( new PlayerIdCard(mImplType, mAttributes, new IPlayerWrapper(this)));
} catch (RemoteException e) {
Log.e(TAG, "Error talking to audio service, player will not be tracked", e);
}
mPlayerIId = newPiid;
}
6.2.2 setDataSource() 代码分析
@ \frameworks\base\media\java\android\media\MediaPlayer.java
public void setDataSource(String path) throws IOException, IllegalArgumentException, SecurityException, IllegalStateException {
setDataSource(path, null, null);
}
private void setDataSource(String path, Map<String, String> headers, List<HttpCookie> cookies)
throws IOException, IllegalArgumentException, SecurityException, IllegalStateException
{
String[] keys = null;
String[] values = null;
if (headers != null) {
keys = new String[headers.size()];
values = new String[headers.size()];
for (Map.Entry<String, String> entry: headers.entrySet()) {
keys[i] = entry.getKey();
values[i] = entry.getValue();
++i;
}
}
setDataSource(path, keys, values, cookies);
}
private void setDataSource(String path, String[] keys, String[] values,List<HttpCookie> cookies)
throws IOException, IllegalArgumentException, SecurityException, IllegalStateException {
final Uri uri = Uri.parse(path);
final String scheme = uri.getScheme();
if ("file".equals(scheme)) {
path = uri.getPath();
} else if (scheme != null) {
// handle non-file sources
nativeSetDataSource( MediaHTTPService.createHttpServiceBinderIfNecessary(path, cookies),
path,keys,values);
return;
}
final File file = new File(path);
if (file.exists()) {
FileInputStream is = new FileInputStream(file);
FileDescriptor fd = is.getFD();
setDataSource(fd);
is.close();
} else {
throw new IOException("setDataSource failed.");
}
}
private native void nativeSetDataSource(
IBinder httpServiceBinder, String path, String[] keys, String[] values)
throws IOException, IllegalArgumentException, SecurityException, IllegalStateException;
6.2.3 prepare() 代码分析
6.2.4 start() 开始播放音乐代码分析
参考：
https://blog.csdn.net/super_dc/article/category/2240809
https://blog.csdn.net/zhuyong006/article/details/86080498
