Develop -- Training(十一) -- 通过NFC共享文件

Android Beam 进场通信，通过 NFC 来分享照片、视频、蓝牙配对，进行一些通信操作。

Android Beam 只有在 Android 版本40.以上，API等级14。

将文件发送到另一台设备

Android Beam 文件传输的要求：

1.Android Beam 传输大文件只能在 Android 4.1（API级别16）和更高可用。

2.文件传输必须要在外部存储。

3.每个文件必须是全部范围可读。可以通过调用方法设置此权限File.setReadable（true ，false）。

4.传输的文件的必须要有文件URI。Android Beam的文件传输无法处理通过 FileProvider.getUriForFile 所产生的内容的URI。

<!--权限申明-->
<uses-permission android:name="android.permission.NFC" />
<uses-permission      android:name="android.permission.READ_EXTERNAL_STORAGE" />

<!--使用NFC功能-->
<uses-feature
android:name="android.hardware.nfc"
android:required="true" />

<!--最低要设置为16以上-->
android:minSdkVersion="16"

检测是否支持 Android Beam 文件传输

public class MainActivity extends Activity {
...
NfcAdapter mNfcAdapter;
// Flag to indicate that Android Beam is available
boolean mAndroidBeamAvailable  = false;
...
@Override
protected void onCreate(Bundle savedInstanceState) {
...
// NFC isn't available on the device
if (!PackageManager.hasSystemFeature(PackageManager.FEATURE_NFC)) {
/*
* Disable NFC features here.
* For example, disable menu items or buttons that activate
* NFC-related features
*/
...
// Android Beam file transfer isn't supported
} else if (Build.VERSION.SDK_INT <
Build.VERSION_CODES.JELLY_BEAN_MR1) {
// If Android Beam isn't available, don't continue.
mAndroidBeamAvailable = false;
/*
* Disable Android Beam file transfer features here.
*/
...
// Android Beam file transfer is available, continue
} else {
mNfcAdapter = NfcAdapter.getDefaultAdapter(this);
...
}
}
...
}

创建提供共享文件的回调方法

public class MainActivity extends Activity {
// List of URIs to provide to Android Beam
private Uri[] mFileUris = new Uri[10];

// Instance that returns available files from this app
private FileUriCallback mFileUriCallback;

mNfcAdapter = NfcAdapter.getDefaultAdapter(this);
/*
* Instantiate a new FileUriCallback to handle requests for URIs
*/
mFileUriCallback = new FileUriCallback();
// Set the dynamic callback for URI requests.
mNfcAdapter.setBeamPushUrisCallback(mFileUriCallback,this);

/**
* Callback that Android Beam file transfer calls to get
* files to share
*/
private class FileUriCallback implements
NfcAdapter.CreateBeamUrisCallback {
public FileUriCallback() {
}
/**
* Create content URIs as needed to share with another device
*/
@Override
public Uri[] createBeamUris(NfcEvent event) {
return mFileUris;
}
}

}

从另一个设备接收文件

Android Beam的 文件传输将文件复制到接收设备上的一个特殊的目录。响应请求显示数据。

通过 Activity 来接收数据处理。

<action android:name="android.intent.action.VIEW" />
<category android:name="android.intent.category.CATEGORY_DEFAULT" />
<data android:mimeType="mime-type" />

读取 Android Beam 文件传输是需要权限的

<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />

处理接收相应的Uri

public class MainActivity extends Activity {
...
// A File object containing the path to the transferred files
private File mParentPath;
// Incoming Intent
private Intent mIntent;
...
/*
* Called from onNewIntent() for a SINGLE_TOP Activity
* or onCreate() for a new Activity. For onNewIntent(),
* remember to call setIntent() to store the most
* current Intent
*
*/
private void handleViewIntent() {
...
// Get the Intent action
mIntent = getIntent();
String action = mIntent.getAction();
/*
* For ACTION_VIEW, the Activity is being asked to display data.
* Get the URI.
*/
if (TextUtils.equals(action, Intent.ACTION_VIEW)) {
// Get the URI from the Intent
Uri beamUri = mIntent.getData();
/*
* Test for the type of URI, by getting its scheme value
*/
if (TextUtils.equals(beamUri.getScheme(), "file")) {
mParentPath = handleFileUri(beamUri);
} else if (TextUtils.equals(
beamUri.getScheme(), "content")) {
mParentPath = handleContentUri(beamUri);
}
}
...
}

// 处理文件的Uri
public String handleFileUri(Uri beamUri) {
// Get the path part of the URI
String fileName = beamUri.getPath();
// Create a File object for this filename
File copiedFile = new File(fileName);
// Get a string containing the file's parent directory
return copiedFile.getParent();
}

// 处理内容的Uri
public String handleContentUri(Uri beamUri) {
// Position of the filename in the query Cursor
int filenameIndex;
// File object for the filename
File copiedFile;
// The filename stored in MediaStore
String fileName;
// Test the authority of the URI
if (!TextUtils.equals(beamUri.getAuthority(), MediaStore.AUTHORITY)) {
/*
* Handle content URIs for other content providers
*/
// For a MediaStore content URI
} else {
// Get the column that contains the file name
String[] projection = { MediaStore.MediaColumns.DATA };
Cursor pathCursor =
getContentResolver().query(beamUri, projection,
null, null, null);
// Check for a valid cursor
if (pathCursor != null &&
pathCursor.moveToFirst()) {
// Get the column index in the Cursor
filenameIndex = pathCursor.getColumnIndex(
MediaStore.MediaColumns.DATA);
// Get the full file name including path
fileName = pathCursor.getString(filenameIndex);
// Create a File object for the filename
copiedFile = new File(fileName);
// Return the parent directory of the file
return new File(copiedFile.getParent());
} else {
// The query didn't work; return null
return null;
}
}
}
}