如何通知我的应用程序从SD卡（Android）删除了一个文件？

调查使用FileObserver

您可以监视单个文件或目录。因此，您要做的就是确定其中包含歌曲的目录并监视每个目录。否则，您可以监视外部存储目录，然后每次更改任何内容时，请检查其是否在数据库中。

它实际上非常简单，类似这样的方法应该起作用：

import android.os.FileObserver;public class SongDeletedFileObserver extends FileObserver {    public String absolutePath;    public MyFileObserver(String path) {        //not sure if you need ALL_EVENTS but it was the only one in the doc listed as a MASK        super(path, FileObserver.ALL_EVENTS);        absolutePath = path;    }    @Override    public void onEvent(int event, String path) {        if (path == null) { return;        }        //a new file or subdirectory was created under the monitored directory        if ((FileObserver.DELETE & event)!=0) { //handle deleted file        }        //data was written to a file        if ((FileObserver.MODIFY & event)!=0) { //handle modified file (maybe id3 info changed?)        }        //the monitored file or directory was deleted, monitoring effectively stops        if ((FileObserver.DELETE_SELF & event)!=0) {//handle when the whole directory being monitored is deleted        }        //a file or directory was opened        if ((FileObserver.MOVED_TO & event)!=0) {//handle moved file        }        //a file or subdirectory was moved from the monitored directory        if ((FileObserver.MOVED_FROM & event)!=0) { //?        }        //the monitored file or directory was moved; monitoring continues        if ((FileObserver.MOVE_SELF & event)!=0) { //?        }    }}

然后，当然，您需要始终运行此FileObserver才能使其生效，因此您需要将其放入服务中。从服务中您会做

SongDeletedFileObserver fileOb = new SongDeletedFileObserver(Environment.getExternalStorageDirectory());

您必须牢记一些棘手的事情：

1. 如果您一直不停地运行，这将使电池消耗更糟。
2. 挂载sdcard时（以及重新启动时），您必须进行同步。这可能很慢