#Building Apps with Content Sharing
- Sharing Simple Data
- Intent && ActionProvider
- 发送数据（发起intent调起其他app处理） + Send Text Content + Send Binary Content + Send Multiple Pieces of Content
- 接收数据
+ AndroidManifest.xml中为Activity定义
<intent-filter>+ 在Activity的onCreate中调用getIntent()获取action、数据，并进行处理 - Sharing Files
- 唯一“安全”的方式就是：将文件对应的URI通过Intent发送出去，并为该URI提供临时的访问权限。而这些步骤都可以通过
FileProvider完成 - 在AndroidManifest.xml中声明provider
xml <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.example.myapp"> <application ...> <provider android:name="android.support.v4.content.FileProvider" android:authorities="com.example.myapp.fileprovider" android:grantUriPermissions="true" android:exported="false"> <meta-data android:name="android.support.FILE_PROVIDER_PATHS" android:resource="@xml/filepaths" /> </provider> ... </application> </manifest> <meta-data>指定描述要分享的目录的xml文件- 指定要分享的目录
xml <paths> <files-path path="images/" name="myimages" /> </paths> <paths>标签可以有多个子标签，<files-path>指定app的files目录下的分享目录名，<external-path>指定外部存储（Environment.getExternalStorageDirectory()）的分享目录名，<cache-path>指定app的cache目录下的分享目录名；分享路径只能在xml中描述；- 如上配置后，需要访问files/images/default_image.jpg时，对应uri为：
content://com.example.myapp.fileprovider/myimages/default_image.jpg - Receive File Requests
+ 定义一个Selection Activity，响应Intent action，例如：
ACTION_PICK<activity android:name=".FileSelectActivity" android:label="@"File Selector" > <intent-filter> <action android:name="android.intent.action.PICK"/> <category android:name="android.intent.category.DEFAULT"/> <category android:name="android.intent.category.OPENABLE"/> <data android:mimeType="text/plain"/> <data android:mimeType="image/*"/> </intent-filter> </activity>
+ 其他app发起该intent，通过`startActivityForResult()`和`onActivityResult()`中发起请求、处理结果
+ 在Selection Activity的onCreate函数中，解析其他app的请求
```java
File requestFile = new File(mImageFilename[position]);
// Use the FileProvider to get a content URI
try {
fileUri = FileProvider.getUriForFile(
MainActivity.this,
"com.example.myapp.fileprovider",
requestFile);
} catch (IllegalArgumentException e) {
Log.e("File Selector",
"The selected file can't be shared: " +
clickedFilename);
}
```
+ 赋予临时访问权限
```java
mResultIntent = new Intent("com.example.myapp.ACTION_RETURN_FILE");
if (fileUri != null) {
// Grant temporary read permission to the content URI
mResultIntent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);
}
```
+ 使用`setFlags()`赋予临时访问权限更安全，`Context.grantUriPermission()`赋予的权限只有手动调用`Context.revokeUriPermission()`才会被移除
+ 返回结果
```java
mResultIntent.setDataAndType(
fileUri,
getContentResolver().getType(fileUri));
// Set the result
MainActivity.this.setResult(Activity.RESULT_OK,
mResultIntent);
finish();
```
- Requesting a Shared File
+ 通常流程是：app发起一个带有请求的intent，分享文件的app的相应Activity被启动，该Activity显示文件列表，用户选择文件后返回被选中的文件的Uri
+ 发起请求
mRequestFileIntent = new Intent(Intent.ACTION_PICK); mRequestFileIntent.setType("image/jpg"); startActivityForResult(mRequestFileIntent, 0);
+ 访问返回的文件
```java
@Override
public void onActivityResult(int requestCode, int resultCode,
Intent returnIntent) {
// If the selection didn't work
if (resultCode != RESULT_OK) {
// Exit without doing anything else
return;
} else {
// Get the file's content URI from the incoming Intent
Uri returnUri = returnIntent.getData();
/*
* Try to open the file for "read" access using the
* returned URI. If the file isn't found, write to the
* error log and return.
*/
try {
/*
* Get the content resolver instance for this context, and use it
* to get a ParcelFileDescriptor for the file.
*/
mInputPFD = getContentResolver().openFileDescriptor(returnUri, "r");
} catch (FileNotFoundException e) {
e.printStackTrace();
Log.e("MainActivity", "File not found.");
return;
}
// Get a regular file descriptor for the file
FileDescriptor fd = mInputPFD.getFileDescriptor();
...
}
}
```
- Retrieving File Information
+ MIME Type
java Uri returnUri = returnIntent.getData(); String mimeType = getContentResolver().getType(returnUri);+ File's Name and Sizejava Uri returnUri = returnIntent.getData(); Cursor returnCursor = getContentResolver().query(returnUri, null, null, null, null); int nameIndex = returnCursor.getColumnIndex(OpenableColumns.DISPLAY_NAME); int sizeIndex = returnCursor.getColumnIndex(OpenableColumns.SIZE); nameView.setText(returnCursor.getString(nameIndex)); sizeView.setText(Long.toString(returnCursor.getLong(sizeIndex))); - Sharing Files with NFC
- Android Beam，大文件传输，from 4.1 API 16
- Android Beam NDEF，小数据传输，from 4.0 API 14
- 发送文件
+ 权限：
<uses-permission android:name="android.permission.NFC" />，<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />+ NFC feature：<uses-feature android:name="android.hardware.nfc" android:required="true" />+ minSdkVersion >= 16 + 检查是否支持if (PackageManager.hasSystemFeature(PackageManager.FEATURE_NFC) && Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1) { mNfcAdapter = NfcAdapter.getDefaultAdapter(this); }
+ 创建提供文件的回调
```java
// List of URIs to provide to Android Beam
private Uri[] mFileUris = new Uri[10];
...
/**
* 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;
}
}
...
// Android Beam file transfer is available, continue
...
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);
...
```
+ 设置需要发送的文件
```java
/*
* Create a list of URIs, get a File,
* and set its permissions
*/
private Uri[] mFileUris = new Uri[10];
String transferFile = "transferimage.jpg";
File extDir = getExternalFilesDir(null);
File requestFile = new File(extDir, transferFile);
requestFile.setReadable(true, false);
// Get a URI for the File and add it to the list of URIs
fileUri = Uri.fromFile(requestFile);
if (fileUri != null) {
mFileUris[0] = fileUri;
} else {
Log.e("My Activity", "No File URI available for file.");
}
```
- 接收文件
+ 设置intent-filter
<activity android:name="com.example.android.nfctransfer.ViewActivity" android:label="Android Beam Viewer" > ... <intent-filter> <action android:name="android.intent.action.VIEW"/> <category android:name="android.intent.category.DEFAULT"/> ... </intent-filter> </activity>
+ 权限：`<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />`
+ 获取接收文件的路径
```java
// 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);
}
}
```
+ 读取
```java
String fileName = beamUri.getPath();
File copiedFile = new File(fileName);
```
+ 根据不同的content provider读取文件
```java
...
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;
}
}
}
...
```