blocks|key|3114533|text|MediaPlayer.java具有同时接受字符串(路径)和FD的setDataSource()签名。它们最终都会变成原生C代码。尽管其中一种方法的效率可能稍高一些，但它可以忽略不计，除非您设置数据源的频率高于每秒一次。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3114534|/**
+*+Sets+the+data+source+(file-path+or+http/rtsp+URL)+to+use.+Call+this+after+
+*+reset(),+or+before+any+other+method+(including+setDataSource())+that+might
+*+throw+IllegalStateException+in+this+class.
+*+
+*+@param+path+the+path+of+the+file,+or+the+http/rtsp+URL+of+the+stream+you+want+to+play
+*+@throws+IllegalStateException+if+it+is+called
+*+in+an+order+other+than+the+one+specified+above
+*/
public+native+void+setDataSource(String+path)+throws+IOException,+IllegalArgumentException,+IllegalStateException;

/**
+*+Sets+the+data+source+(FileDescriptor)+to+use.+It+is+the+caller's+responsibility
+*+to+close+the+file+descriptor.+It+is+safe+to+do+so+as+soon+as+this+call+returns.
+*+Call+this+after+reset(),+or+before+any+other+method+(including+setDataSource())+
+*+that+might+throw+IllegalStateException+in+this+class.
+*+
+*+@param+fd+the+FileDescriptor+for+the+file+you+want+to+play
+*+@throws+IllegalStateException+if+it+is+called
+*+in+an+order+other+than+the+one+specified+above
+*/
public+void+setDataSource(FileDescriptor+fd)+
++++++++throws+IOException,+IllegalArgumentException,+IllegalStateException+{
++++//+intentionally+less+than+LONG_MAX
++++setDataSource(fd,+0,+0x7ffffffffffffffL);
}

/**
+*+Sets+the+data+source+(FileDescriptor)+to+use.++It+is+the+caller's+responsibility
+*+to+close+the+file+descriptor.+It+is+safe+to+do+so+as+soon+as+this+call+returns.
+*+Call+this+after+reset(),+or+before+any+other+method+(including+setDataSource())+
+*+that+might+throw+IllegalStateException+in+this+class.
+*+
+*+@param+fd+the+FileDescriptor+for+the+file+you+want+to+play
+*+@param+offset+the+offset+into+the+file+where+the+data+to+be+played+starts,+in+bytes
+*+@param+length+the+length+in+bytes+of+the+data+to+be+played
+*+@throws+IllegalStateException+if+it+is+called
+*+in+an+order+other+than+the+one+specified+above
+*/
public+native+void+setDataSource(FileDescriptor+fd,+long+offset,+long+length)+
++++++++throws+IOException,+IllegalArgumentException,+IllegalStateException;|code-block|syntax|javascript|3114535|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

MediaPlayer.java has setDataSource() signatures that accept both a String (path) and an FD.
They both eventually go into native C code. Although one of these may be SLIGHTLY more efficient it will be negligible unless you're setting your data source more often than once a second. 

<pre><code>/**
 * Sets the data source (file-path or http/rtsp URL) to use. Call this after 
 * reset(), or before any other method (including setDataSource()) that might
 * throw IllegalStateException in this class.
 * 
 * @param path the path of the file, or the http/rtsp URL of the stream you want to play
 * @throws IllegalStateException if it is called
 * in an order other than the one specified above
 */
public native void setDataSource(String path) throws IOException, IllegalArgumentException, IllegalStateException;

/**
 * Sets the data source (FileDescriptor) to use. It is the caller's responsibility
 * to close the file descriptor. It is safe to do so as soon as this call returns.
 * Call this after reset(), or before any other method (including setDataSource()) 
 * that might throw IllegalStateException in this class.
 * 
 * @param fd the FileDescriptor for the file you want to play
 * @throws IllegalStateException if it is called
 * in an order other than the one specified above
 */
public void setDataSource(FileDescriptor fd) 
 throws IOException, IllegalArgumentException, IllegalStateException {
 // intentionally less than LONG_MAX
 setDataSource(fd, 0, 0x7ffffffffffffffL);
}

/**
 * Sets the data source (FileDescriptor) to use. It is the caller's responsibility
 * to close the file descriptor. It is safe to do so as soon as this call returns.
 * Call this after reset(), or before any other method (including setDataSource()) 
 * that might throw IllegalStateException in this class.
 * 
 * @param fd the FileDescriptor for the file you want to play
 * @param offset the offset into the file where the data to be played starts, in bytes
 * @param length the length in bytes of the data to be played
 * @throws IllegalStateException if it is called
 * in an order other than the one specified above
 */
public native void setDataSource(FileDescriptor fd, long offset, long length) 
 throws IOException, IllegalArgumentException, IllegalStateException;
</code></pre>

blocks|key|236973|text|实际上，事实证明在某些情况下是有区别的。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|236974|调用mediaPlayer.prepare()时，如果您尝试从getApplicationContext().getFilesDir()加载文件，则mediaPlayer.setDataSource(String+path)将失败，具体取决于文件的保存方式。例如，如果我使用new+RandomAccessFile(filePath,+"rw")编写一个文件，如果您使用mediaPlayer.setDataSource(String+path)，那么该文件实际上不能被mediaplayer读取。prepare()将立即从mediaplayer触发error(1,+-2147483648)；本质上是一个文件权限错误。SDK9引入了file.setReadable+(boolean+readable,+boolean+ownerOnly)，它可能允许您通过将ownerOnly设置为false...but来解决此问题，但如果您需要支持较旧的SDK，这对您没有帮助。|offset|length|style|CODE|236975|但是，mediaPlayer.setDataSource(FileDescriptor+fd)没有这个问题，mediaplayer将成功地准备完全相同的文件，而不会出现权限问题。|236976|entityMap^0|0|2|L|V|11|22|12|3T|10|55|12|6X|9|7N|L|8T|1I|AL|9|0|3|18|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|M|8|@$D|N|E|O|F|G]|$D|P|E|Q|F|G]|$D|R|E|S|F|G]|$D|T|E|U|F|G]|$D|V|E|W|F|G]|$D|X|E|Y|F|G]|$D|Z|E|10|F|G]|$D|11|E|12|F|G]|$D|13|E|14|F|G]]|9|@]|A|$]]|$1|H|3|I|5|6|7|15|8|@$D|16|E|17|F|G]]|9|@]|A|$]]|$1|J|3|-4|5|6|7|18|8|@]|9|@]|A|$]]]|K|$]]

Actually, it turns out that there IS a difference in certain situations.

<code>mediaPlayer.setDataSource(String path)</code> will fail when you call <code>mediaPlayer.prepare()</code>, if you are trying to load a file from <code>getApplicationContext().getFilesDir()</code>, depending on how the file was saved. For example, if I write a file using <code>new RandomAccessFile(filePath, "rw")</code>, the file is not actually readable by the mediaplayer if you use <code>mediaPlayer.setDataSource(String path)</code>. The <code>prepare()</code> will immediately trigger <code>error(1, -2147483648)</code> from the mediaplayer; essentially a file permission error. SDK 9 introduced <code>file.setReadable (boolean readable, boolean ownerOnly)</code> which would presumably allow you to resolve this issue by setting <code>ownerOnly</code> to false...but that doesn't help you if you need to support older SDKs.

HOWEVER, <code>mediaPlayer.setDataSource(FileDescriptor fd)</code> does NOT have this problem and mediaplayer will successfully prepare the same exact file without a permission problem.

Let's say I have a full path to a file. Which is the better approach to loading that file into a MediaPlayer? 

<pre><code>String filePath = "somepath/somefile.mp3";
mediaPlayer.setDataSource(filePath);
</code></pre>

OR

<pre><code>String filePath = "somepath/somefile.mp3";
File file = new File(filePath);
FileInputStream inputStream = new FileInputStream(file);
mediaPlayer.setDataSource(inputStream.getFD());
inputStream.close();
</code></pre>

Does it matter? Simply using the path seems easier but is there a reason to do the extra work to use a FileDescriptor?

MediaPlayer setDataSource, better to use path or FileDescriptor?

假设我有一个文件的完整路径。将该文件加载到MediaPlayer中，哪种方法更好？String filePath = "somepath/somefile.mp3";mediaPlayer.setDataSource(filePath);或String filePath = "somepath/somefile.mp3...

问MediaPlayer setDataSource，最好使用path还是FileDescriptor？
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问MediaPlayer setDataSource，最好使用path还是FileDescriptor？
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