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;
             }
        }
    }
}