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；

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//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

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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));

}

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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);

}