Android创建一个文件夹和文件

public class MainActivity extends Activity {

URLConnection connection;
 int DownedFileLength=0; 
    InputStream  inputStream;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

  //  Thread threes=new Thread(runable);
  //  threes.start();
    Button button=(Button)findViewById(R.id.button);
    button.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View arg0) {
            // TODO Auto-generated method stub
            String savePAth=Environment.getExternalStorageDirectory()+"/text.mp3";     
             System.out.println(savePAth);
             File file1=new File(savePAth);     
             if (!file1.exists()) { file1.mkdir(); }     
                 if (!file1.exists()) {         
                     try {                
                         file1.createNewFile();     
                         } catch (Exception e) {              
                             System.out.println("---test------创建文件");
                             e.printStackTrace();          
                             }        
                 }
        }

        //Player();
    });

}


@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}

Runnable runable=new Runnable() {
    @Override
    public void run() {
       DownFile("http://172.20.35.218:8090/mpthree/345.mp3");
//  System.out.println("获取的");
    }
};

 /**
 * @param urlString
 */
private void DownFile(String urlString)     {  

     try {             
         URL url=new URL(urlString);    
         connection=url.openConnection(); 
         inputStream=connection.getInputStream();      
         } catch (Exception e) {    e.printStackTrace();  
         System.out.println("61---URL创建连接");   }       

String savePAth=Environment.getExternalStorageDirectory()+"/music/";

     File file1=new File(savePAth);     
//   if (!file1.exists()) {    
         file1.mkdir();        
    //   }      
     System.out.println(savePAth);

String savePathString=Environment.getExternalStorageDirectory()+"/music/345.mp3";
File file =new File(savePathString);

if (!file.exists()) {

try {

file.createNewFile();

} catch (Exception e) {

System.out.println("---76------创建文件");
e.printStackTrace();

}

}else{
file.delete();
try {
file.createNewFile();
} catch (IOException e) {
System.out.println("---84------删除--创建文件");
e.printStackTrace();
}

}

try {          
     OutputStream  outputStream=new FileOutputStream(file);   
    byte [] buffer=new byte[1024*4];         
    int FileLength=connection.getContentLength();     

    while (DownedFileLength<FileLength) {           
        outputStream.write(buffer);               
        DownedFileLength+=inputStream.read(buffer);  

        }       
    outputStream.close();
        } catch (Exception e) {    
             System.out.println("---97----下载过程");
            e.printStackTrace();   
            }

System.out.println("-------下载完成。");

} 

public void Player(){
    MediaPlayer mediaPlayer=new MediaPlayer();
    mediaPlayer.reset();
    try {
        File file = new File("/sdcard/music/345.mp3"); 
        FileInputStream fis = new FileInputStream(file); 
        mediaPlayer.setDataSource(fis.getFD()); 


        mediaPlayer.prepare();
    } catch (IllegalArgumentException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (SecurityException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (IllegalStateException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

    mediaPlayer.start();
    System.out.println("-------播放完成。");
}

}

  <uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<uses-permission android:name="android.permission.WAKE_LOCK"/>

                 }![图片说明](https://img-ask.csdn.net/upload/201503/17/1426565721_200306.png)

你添加内存读写权限了吗?

如果回答对您有帮助，请采纳

看下错误信息，是权限还是路径问题

不好意思，我找到原因了，代码没错，权限也有，是我新建的模拟器忘记设置SD卡的大小了，所以模拟器没有SD卡。。希望大家不要犯像我这样的低级错误，还害得我找了2天错