Android Studio 音乐播放器无法从 sdcard 中读取，只能从内存中读取 [英] Android Studio music player cant read from sdcard, only internal memory

问题描述

如果这被证明是一个愚蠢的问题，我深表歉意，这可能是一个快速解决方案，但我就是想不通.我正在 android studio 中构建一个音乐播放器，sdcard 上的所有歌曲都没有显示在列表视图中，只有内存中的歌曲，即使我确实实现了 getExternalStorageDirectory() 并在清单文件中添加了权限.非常感谢对此或建设性批评的任何投入.这是主要的java类.

公共类 MainActivity 扩展 AppCompatActivity {ListView lv;字符串[] 项；@覆盖protected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);lv = (ListView) findViewById(R.id.lvPlayList);//--------------------------------------------->V 这里 V <-------------------------最终的 ArrayList<文件>mySongs = findSongs(Environment.getExternalStorageDirectory());//----------------------------------------------------------------------------------items = new String[ mySongs.size() ];for(int i = 0; i<mySongs.size(); i++) {toast(mySongs.get(i).getName().toString());items[i] = mySongs.get(i).getName().toString().replace(".mp3", "").replace(".wav", "");}ArrayAdapteradp = new ArrayAdapter<>(getApplicationContext(), R.layout.song_layout, R.id.textView, items);lv.setAdapter(adp);lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {@覆盖public void onItemClick(AdapterView<?> parent, View view, int position, long id) {startActivity(new Intent(getApplicationContext(), Player.class).putExtra("pos",position).putExtra("songlist",mySongs));}});}公共 ArrayList<文件>findSongs(文件根){ArrayList<文件>al = new ArrayList<>();File[] 文件 = root.listFiles();for(文件单文件:文件){if(singleFile.isDirectory() && !singleFile.isHidden()) {al.addAll(findSongs(singleFile));} 别的 {if(singleFile.getName().endsWith(".mp3") || singleFile.getName().endsWith(".wav")) {al.add(singleFile);}}}返回 al;}公共无效吐司(字符串文本){Toast.makeText(getApplicationContext(), text, Toast.LENGTH_SHORT).show();}}

解决方案

使用此方法从您的设备获取 filePath 列表

 ArrayListfindSongs(String rootPath) {ArrayListfileList = new ArrayList<>();尝试{文件根文件夹 = 新文件(根路径)；File[] 文件 = rootFolder.listFiles();//如果目录不包含任何文件，您将在这里获得NPE，像这样处理它.对于(文件文件:文件){如果(文件.isDirectory()){如果 (findSongs(file.getAbsolutePath()) != null) {fileList.addAll(findSongs(file.getAbsolutePath()));} 别的 {休息;}} else if (file.getName().endsWith(".mp3")) {fileList.add(file.getAbsolutePath());}}返回文件列表；}catch(异常e){返回空；}}

但是您需要从 sdCard 获取文件，为此传递/storage/sdcard1/"作为 findSongs(String path) 方法的参数，如下所示:

onCreate(Bundle svaeInstance){……………………if(findSongs("/storage/sdcard1/")!=null){ArrayListlistOfFilePath=findSongs("/storage/sdcard1/");//在这里你会得到所有包含 .mp3 的文件路径.//做剩下的事情}else { Toast.makeText(this, "sdCard not available", Toast.LENGTH_SHORT).show();}......}

<块引用>

注意:使用/storage/sdcard1/"从sdCard读取文件，使用Environment.getExternalStorageDirectory().getAbsolutePath()从手机内存读取文件.

希望对你有帮助.

I apologize if this turns out to be a stupid question, it might turn out as a quick fix but I just cant figure it out. I'm building a music player in android studio and none of the songs on the sdcard dont show up in the list view, only the ones in internal memory, even though I did implement getExternalStorageDirectory() and added the permission in the manifest file. Any input on this or constructive criticism is greatly apreciated. Here is the main java class.

public class MainActivity extends AppCompatActivity {

    ListView lv;
    String[] items;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        lv = (ListView) findViewById(R.id.lvPlayList);

        //---------------------------------------------> V HERE V <-------------------------

        final ArrayList<File> mySongs = findSongs(Environment.getExternalStorageDirectory());
        //----------------------------------------------------------------------------------
        items = new String[ mySongs.size() ];

        for(int i = 0; i<mySongs.size(); i++) {
            toast(mySongs.get(i).getName().toString());
            items[i] = mySongs.get(i).getName().toString().replace(".mp3", "").replace(".wav", "");
        }

        ArrayAdapter<String> adp = new ArrayAdapter<>(getApplicationContext(), R.layout.song_layout, R.id.textView, items);
        lv.setAdapter(adp);
        lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                startActivity(new Intent(getApplicationContext(), Player.class).putExtra("pos",position).putExtra("songlist",mySongs));
            }
        });
    }

    public ArrayList<File> findSongs(File root) {
        ArrayList<File> al = new ArrayList<>();
        File[] files = root.listFiles();
        for(File singleFile : files) {
            if(singleFile.isDirectory() && !singleFile.isHidden()) {
                al.addAll(findSongs(singleFile));
            } else {
                if(singleFile.getName().endsWith(".mp3") || singleFile.getName().endsWith(".wav")) {
                    al.add(singleFile);
                }
            }
        }
        return al;
    }

    public void toast(String text) {
        Toast.makeText(getApplicationContext(), text, Toast.LENGTH_SHORT).show();
    }
}

解决方案

Use this method to get the list of filePath from your device

 ArrayList<String> findSongs(String rootPath) {
    ArrayList<String> fileList = new ArrayList<>();
    try{
       File rootFolder = new File(rootPath);
       File[] files = rootFolder.listFiles(); //here you will get NPE if directory doesn't contains  any file,handle it like this.
       for (File file : files) {
         if (file.isDirectory()) {
               if (findSongs(file.getAbsolutePath()) != null) {
                    fileList.addAll(findSongs(file.getAbsolutePath()));
                } else {
                    break;
                }
         } else if (file.getName().endsWith(".mp3")) {
             fileList.add(file.getAbsolutePath());
         }
    }
    return fileList;
    }catch(Exception e){
       return null;
    }
}

but you need to get files from sdCard, for that pass "/storage/sdcard1/" as the parameter for findSongs(String path) method like this:

onCreate(Bundle svaeInstance){
 ........
 ........
  if(findSongs("/storage/sdcard1/")!=null){
    ArrayList<String> listOfFilePath=findSongs("/storage/sdcard1/"); // here you will get all the files path which contains .mp3 at the end.
 //do the remaining stuff
  }else { Toast.makeText(this, "sdCard not available", Toast.LENGTH_SHORT).show();
  }
 ......
}

Note: use "/storage/sdcard1/" for reading files from sdCard and use Environment.getExternalStorageDirectory().getAbsolutePath() for reading files from phone memory.

Hope this will help you.

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