MediaScannerReceiver

转载自：http://blog.csdn.net/qikaibinglan/article/details/6123403

源码android/packages/apps/providers/media/src/com/android/providers/media/MediaScannerReceiver.java

package com.android.providers.media;

import android.content.Context;

import android.content.Intent;

import android.content.BroadcastReceiver;

import android.net.Uri;

import android.os.Environment;

import android.os.Bundle;

import java.io.File;

public class MediaScannerReceiver extends BroadcastReceiver

{

private final static String TAG = "MediaScannerReceiver";

@Override

public void onReceive(Context context, Intent intent) {

String action = intent.getAction();

Uri uri = intent.getData();

String externalStoragePath = Environment.getExternalStorageDirectory().getPath();

if (action.equals(Intent.ACTION_BOOT_COMPLETED)) {

// scan internal storage

scan(context, MediaProvider.INTERNAL_VOLUME);

// scan external storage if it is mounted

String state = Environment.getExternalStorageState();

if (Environment.MEDIA_MOUNTED.equals(state) ||

Environment.MEDIA_MOUNTED_READ_ONLY.equals(state)) {

scan(context, MediaProvider.EXTERNAL_VOLUME);

}

} else {

if (uri.getScheme().equals("file")) {

// handle intents related to external storage

String path = uri.getPath();

if (action.equals(Intent.ACTION_MEDIA_MOUNTED) &&

externalStoragePath.equals(path)) {

scan(context, MediaProvider.EXTERNAL_VOLUME);

} else if (action.equals(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE) &&

path != null && path.startsWith(externalStoragePath + "/")) {

scanFile(context, path);

}

}

}

}

private void scan(Context context, String volume) {

Bundle args = new Bundle();

args.putString("volume", volume);

context.startService(

new Intent(context, MediaScannerService.class).putExtras(args));

}

private void scanFile(Context context, String path) {

Bundle args = new Bundle();

args.putString("filepath", path);

context.startService(

new Intent(context, MediaScannerService.class).putExtras(args));

}

}

从上面的源码可以总结以下几点：

1，action.equals(Intent.ACTION_BOOT_COMPLETED)

每当机器boot完之后就会发出Intent.ACTION_BOOT_COMPLETED，而在MediaScannerReceiver 接到该Action之后就对Internal 和External(若Sdcard挂载了)扫描，将其数据扫描到对应的数据库。所以你在开发的时候，每次开模拟器或手机你注意Logcat信息，就可以发现：scanner Internal Volumn...等等相关信息

2，uri.getScheme().equals("file")

除了接受机器boot完的Action要去扫描，还接受了以file中的两种扫描：扫描External和扫描一个文件：

1)

action.equals(Intent.ACTION_MEDIA_MOUNTED) &&

externalStoragePath.equals(path)[/color])

scan(context, MediaProvider.EXTERNAL_VOLUME);

2)

Intent.ACTION_MEDIA_SCANNER_SCAN_FILE) &&

path != null[/color] && path.startsWith(externalStoragePath + "/")) {

scanFile(context, path)

我们可以找到android自带ap的里运用了这种，就是Deve Tool里的Media Scanner,其扫描Sdcard:

其源码：apps›Development›src›com›android›development›MediaScannerActivity.java

Java代码

package com.android.development;

import android.app.Activity;

import android.content.Context;

import android.content.Intent;

import android.content.IntentFilter;

import android.content.BroadcastReceiver;

import android.net.Uri;

import android.os.Environment;

import android.widget.TextView;

public class MediaScannerActivity extends Activity

{

public MediaScannerActivity() {

}

/** Called when the activity is first created or resumed. */

@Override

public void onResume() {

super.onResume();

setContentView(R.layout.media_scanner_activity);

[color=red]IntentFilter intentFilter = new IntentFilter(Intent.ACTION_MEDIA_SCANNER_STARTED);

intentFilter.addAction(Intent.ACTION_MEDIA_SCANNER_FINISHED);

intentFilter.addDataScheme("file");

registerReceiver(mReceiver, intentFilter)[/color];

sendBroadcast(new Intent(Intent.ACTION_MEDIA_MOUNTED, Uri.parse("file://"

+ Environment.getExternalStorageDirectory())));

mTitle = (TextView) findViewById(R.id.title);

mTitle.setText("Sent ACTION_MEDIA_MOUNTED to trigger the Media Scanner.");

}

/** Called when the activity going into the background or being destroyed. */

@Override

public void onPause() {

super.onPause();

unregisterReceiver(mReceiver);

}

private final BroadcastReceiver mReceiver = new BroadcastReceiver() {

@Override

public void onReceive(Context context, Intent intent) {

if (intent.getAction().equals(Intent.ACTION_MEDIA_SCANNER_STARTED)) {

mTitle.setText("Media Scanner started scanning " + intent.getData().getPath());

}

else if (intent.getAction().equals(Intent.ACTION_MEDIA_SCANNER_FINISHED)) {

mTitle.setText("Media Scanner finished scanning " + intent.getData().getPath());

}

}

};

private TextView mTitle;

}