Android sd卡状态监听，文件搜索，媒体文件刷新

整理一下关于sd卡相关知识点，主要包括sd卡状态监听，sd卡文件搜索，sd卡媒体数据库（系统支持媒体类型）刷新模块：

一：sd卡状态进行监听

有时程序进行外部数据读取和写入时，为防止异常发生需要对sd卡状态进行监听，对于sd卡的状态我们可以采用注册广播来实现

下面是文档中一个经典例子；

[java] view plaincopy在CODE上查看代码片派生到我的代码片

//监听sdcard状态广播     BroadcastReceiver mExternalStorageReceiver;     //sdcard可用状态     boolean mExternalStorageAvailable = false;     //sdcard可写状态     boolean mExternalStorageWriteable = false;     void updateExternalStorageState() {         //获取sdcard卡状态         String state = Environment.getExternalStorageState();         if (Environment.MEDIA_MOUNTED.equals(state)) {             mExternalStorageAvailable = mExternalStorageWriteable = true;         } else if (Environment.MEDIA_MOUNTED_READ_ONLY.equals(state)) {             mExternalStorageAvailable = true;             mExternalStorageWriteable = false;         } else {             mExternalStorageAvailable = mExternalStorageWriteable = false;         }     }     //开始监听     void startWatchingExternalStorage() {         mExternalStorageReceiver = new BroadcastReceiver() {             @Override             public void onReceive(Context context, Intent intent) {                 Log.i("test", "Storage: " + intent.getData());                 updateExternalStorageState();             }         };         IntentFilter filter = new IntentFilter();         filter.addAction(Intent.ACTION_MEDIA_MOUNTED);         filter.addAction(Intent.ACTION_MEDIA_REMOVED);         registerReceiver(mExternalStorageReceiver, filter);         updateExternalStorageState();     }     //停止监听     void stopWatchingExternalStorage() {         unregisterReceiver(mExternalStorageReceiver);     }  

二：sdcard下搜索某一类型（通常是后缀名相同）文件，或是指定文件名的查找功能

（1）搜索指定文件

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public String searchFile(String filename){            String res="";            File[] files=new File("/sdcard").listFiles();            for(File f:files){                if(f.isDirectory())                    searchFile(f.getName());                else                if(f.getName().indexOf(filename)>=0)                    res+=f.getPath()+"\n";            }            if(res.equals(""))                res="file can't find!";            return res;        }    

（2）指定相同后缀名称文件类型

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private List<String> files = new ArrayList<String>();    class FindFilter implements FilenameFilter {        public boolean accept(File dir, String name) {            return (name.endsWith(".txt"));        }    }    public void updateList() {         File home = new File("/sdcard/");      if (home.listFiles( new FindFilter()).length > 0) {          for (File file : home.listFiles( new FindFilter())) {           files.add(file.getName());    

三：媒体数据库的刷新，

当android的系统启动的时候，系统会自动扫描sdcard内的文件，并把获得的媒体文件信息保存在一个系统媒体数据库中，
程序想要访问多媒体文件，就可以直接访问媒体数据库中即可，而用直接去sdcard中取。
但是，如果系统在不重新启动情况下，媒体数据库信息是不会更新的，这里举个例子，当应用程序保存一张图片到本地后（已成功），
但打开系统图片库查看时候，你会发现图片库内并没有你刚刚保存的那张图片，原因就在于系统媒体库没有及时更新，这时就需要手动刷新文件系统了

方式一：发送一广播信息通知系统进行文件刷新

[java] view plaincopy在CODE上查看代码片派生到我的代码片

private void scanSdCard(){               IntentFilter intentfilter = new IntentFilter(Intent.ACTION_MEDIA_SCANNER_STARTED);               intentfilter.addAction(Intent.ACTION_MEDIA_SCANNER_FINISHED);               intentfilter.addDataScheme("file");                       registerReceiver(scanSdReceiver, intentfilter);               Intent intent = new Intent();               intent.setAction(Intent.ACTION_MEDIA_MOUNTED);               intent.setData(Uri.parse("file://" + Environment.getExternalStorageDirectory().getAbsolutePath()));               sendBroadcast(intent);           }           private BroadcastReceiver scanSdReceiver = new BroadcastReceiver(){               private AlertDialog.Builder builder;               private AlertDialog ad;               @Override               public void onReceive(Context context, Intent intent) {                   String action = intent.getAction();                   if(Intent.ACTION_MEDIA_SCANNER_STARTED.equals(action)){                       builder = new AlertDialog.Builder(context);                       builder.setMessage("正在扫描sdcard...");                       ad = builder.create();                       ad.show();                   //    adapter.notifyDataSetChanged();                   }else if(Intent.ACTION_MEDIA_SCANNER_FINISHED.equals(action)){                       ad.cancel();//重新获取文件数据信息                       Toast.makeText(context, "扫描完毕", Toast.LENGTH_SHORT).show();               }              }       };    

或者

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public void fileScan(File file){              Uri data =  Uri.parse("file://"+ Environment.getExternalStorageDirectory())        sendBroadcast(new Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE, data));          }     

[java] view plaincopy在CODE上查看代码片派生到我的代码片

void insertMeadia(ContentValues values){             Uri uri = getContentResolver().insert( MediaStore.Video.Media.EXTERNAL_CONTENT_URI, values);              sendBroadcast(new Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE, uri));        }    

刷新所有系统文件，效率可能不高，高效方法是只刷新变化的文件

方式二：指定特定文件操作

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File path = getExternalFilesDir(Environment.DIRECTORY_PICTURES);           File file = new File(path, "DemoPicture.jpg");           try {               InputStream is = getResources().openRawResource(R.drawable.balloons);               OutputStream os = new FileOutputStream(file);               byte[] data = new byte[is.available()];               is.read(data);               os.write(data);               is.close();               os.close();               // Tell the media scanner about the new file so that it is               // immediately available to the user.               MediaScannerConnection.scanFile(this,                       new String[] { file.toString() }, null,                       new MediaScannerConnection.OnScanCompletedListener() {                   public void onScanCompleted(String path, Uri uri) {                       Log.i("ExternalStorage", "Scanned " + path + ":");                       Log.i("ExternalStorage", "-> uri=" + uri);                   }               });           } catch (IOException e) {               // Unable to create file, likely because external storage is               // not currently mounted.               Log.w("ExternalStorage", "Error writing " + file, e);           }