问题描述

Android创建一个文件夹和文件

public class MainActivity extends Activity {

URLConnection connection; int DownedFileLength=0;     InputStream  inputStream;@Overrideprotected 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();    });}@Overridepublic 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](http://img.ask.csdn.net/upload/201503/17/1426565721_200306.png)

解决方案

看下错误信息，是权限还是路径问题

解决方案二：
你添加内存读写权限了吗?

如果回答对您有帮助，请采纳

解决方案三：
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