实战-Android 蓝牙文件分享

需求
在文件管理中，增加一个通过蓝牙分享图片的功能

实现
Android蓝牙分享已经有现成的功能实现，直接上代码：

private void blueToothSendFile() {try {Intent localIntent = null;localIntent = new Intent();localIntent.setAction(Intent.ACTION_SEND);File tempfiles = new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES),"1.png");if(!tempfiles.exists()){return;}Uri contentUri = FileProvider.getUriForFile(Objects.requireNonNull(getActivity()).getApplicationContext(), "xx.xx.xxx.fileprovider", tempfiles);localIntent.setType("image/*");localIntent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION |Intent.FLAG_GRANT_WRITE_URI_PERMISSION);localIntent.setPackage("com.android.bluetooth");localIntent.putExtra(Intent.EXTRA_STREAM, contentUri);startActivityForResult(localIntent, 9527);}catch (Exception e){e.printStackTrace();}}

踩坑

这里记录一下里面需要特别注意的几点：

1、FileUriExposedException

在7.0的以上的系统中，尝试传递 file://URI可能会触发FileUriExposedException，原始代码如下：

Uri contentUri = Uri.fromFile(tempfiles);

异常如下：

01-06 11:45:20.798  9486  9486 W System.err: android.os.FileUriExposedException: file:///storage/emulated/0/Pictures/1.png exposed beyond app through ClipData.Item.getUri()
01-06 11:45:20.798  9486  9486 W System.err:    at android.os.StrictMode.onFileUriExposed(StrictMode.java:1978)
01-06 11:45:20.799  9486  9486 W System.err:    at android.net.Uri.checkFileUriExposed(Uri.java:2371)
01-06 11:45:20.799  9486  9486 W System.err:    at android.content.ClipData.prepareToLeaveProcess(ClipData.java:963)
01-06 11:45:20.799  9486  9486 W System.err:    at android.content.Intent.prepareToLeaveProcess(Intent.java:10219)
01-06 11:45:20.799  9486  9486 W System.err:    at android.content.Intent.prepareToLeaveProcess(Intent.java:10204)
01-06 11:45:20.799  9486  9486 W System.err:    at android.app.Instrumentation.execStartActivity(Instrumentation.java:1667)
01-06 11:45:20.799  9486  9486 W System.err:    at android.app.Activity.startActivityForResult(Activity.java:4621)

解决方案就是使用官方推荐的FileProvider
可以加个判断：

if (Build.VERSION.SDK_INT >= 24) {//android 7.0以上uri = FileProvider.getUriForFile(activity, BuildConfig.APPLICATION_ID.concat(".fileProvider"), file);//android:authorities="${applicationId}.fileProvider"} else {uri = Uri.fromFile(file);}

2、FileProvider

1) 声明FIleProvider
2) 编写XML文件
3) 使用FileProvider

1 ) 、AndroidManifest.xml 中声明FileProvider，并在meta-data，里面指向一个xml文件

<providerandroid:name="android.support.v4.content.FileProvider"android:authorities="packagename.fileProvider"//${applicationId}.fileProviderandroid:grantUriPermissions="true"android:exported="false"><meta-dataandroid:name="android.support.FILE_PROVIDER_PATHS"android:resource="@xml/file_paths" />
</provider>

2 )、编写XML文件file_paths.xml

<?xml version="1.0" encoding="utf-8"?>
<paths xmlns:android="http://schemas.android.com/apk/res/android"><root-path name="root" path="" /><files-path name="files" path="." /><cache-path name="cache" path="." /><external-path name="external" path="." /><external-files-path name="name1" path="." /><external-cache-path name="name2" path="." />
</paths>

为什么要写这么个xml文件？

使用content://uri替代file://uri，那么，content://的uri如何定义呢？总不能使用文件路径.
所以，需要一个虚拟的路径对文件路径进行映射，需要编写一个xml文件，通过path以及xml节点确定可访问的目录，通过name属性来映射真实的文件路径

节点的定义：

public class FileProvider extends ContentProvider {private static final String[] COLUMNS = {OpenableColumns.DISPLAY_NAME, OpenableColumns.SIZE };private static final StringMETA_DATA_FILE_PROVIDER_PATHS = "android.support.FILE_PROVIDER_PATHS";private static final String TAG_ROOT_PATH = "root-path"; //--设备根目录 /private static final String TAG_FILES_PATH = "files-path"; // --/data/data/<包名>/filesprivate static final String TAG_CACHE_PATH = "cache-path"; // --/data/data/<包名>/cacheprivate static final String TAG_EXTERNAL = "external-path";//--/storage/emulate/0private static final String TAG_EXTERNAL_FILES = "external-files-path";// --/storage/emulate/0/Android/data/<包名>/filesprivate static final String TAG_EXTERNAL_CACHE = "external-cache-path"; ///storage/emulate/0/Android/data/<包名>/cacheprivate static final String TAG_EXTERNAL_MEDIA = "external-media-path";private static final String ATTR_NAME = "name";private static final String ATTR_PATH = "path";

3）、使用FileProvider

Uri contentUri = FileProvider.getUriForFile(Context, "xx.xx.xxx.fileprovider", tempfiles);

3、Permission Denial: that is not exported from UID 1000

01-01 06:37:41.322 W/InstallStaging( 2110): java.lang.SecurityException: Permission Denial: opening provider android.support.v4.content.FileProvider from ProcessRecord{56d9d3c 2110:com.android.packageinstaller/u0a19} (pid=2110, uid=10019) that is not exported from UID 1000
01-01 06:37:41.322 W/InstallStaging( 2110):     at android.os.Parcel.readException(Parcel.java:2005)
01-01 06:37:41.322 W/InstallStaging( 2110):     at android.os.Parcel.readException(Parcel.java:1951)

看打印，not exported，是否可以设置android:exported="true"呢，答案是否定的，会报错。

java.lang.RuntimeException: Unable to get provider android.support.v4.content.FileProvider: java.lang.SecurityException: Provider must not be exported

解决方案有两种：
1)、grantUriPermission

grantUriPermission("com.android.bluetooth",contentUri,Intent.FLAG_GRANT_READ_URI_PERMISSION|Intent.FLAG_GRANT_WRITE_URI_PERMISSION);

2)、addFlags

Intent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION | Intent.FLAG_GRANT_WRITE_URI_PERMISSION);

添加之后还是报错：

01-01 06:37:41.208 W/ActivityManager(  680): For security reasons, the system cannot issue a Uri permission grant to content://xxxxxxx.fileprovider/download/QQ.apk [user 0]; use startActivityAsCaller() instead

frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java

int checkGrantUriPermissionLocked(int callingUid, String targetPkg, GrantUri grantUri,final int modeFlags, int lastTargetUid) {...if ((callingAppId == SYSTEM_UID) || (callingAppId == ROOT_UID)) {if ("com.android.settings.files".equals(grantUri.uri.getAuthority())) {// Exempted authority for// 1. cropping user photos and sharing a generated license html//    file in Settings app// 2. sharing a generated license html file in TvSettings app} else {Slog.w(TAG, "For security reasons, the system cannot issue a Uri permission"+ " grant to " + grantUri + "; use startActivityAsCaller() instead");return -1;}}

可以看到，如果是SYSTEM_UID 或者ROOT_UID 的应用，只有com.android.settings.files这个FileProvider才添加权限成功。

android:sharedUserId="android.uid.system"

那么我们如果是普通应该，不是system UID，可不会报错，如果是sharedUserId ： system，我们可能需要修改ActivityManagerService.java这里，把自己生命的FileProvider添加进去，比如我的修改：

if ("com.android.settings.files".equals(grantUri.uri.getAuthority())
+          ||grantUri.uri.getAuthority().contains("funtvfileprovider")) {// Exempted authority for// 1. cropping user photos and sharing a generated license html//    file in Settings app// 2. sharing a generated license html file in TvSettings app} else {Slog.w(TAG, "For security reasons, the system cannot issue a Uri permission"+ " grant to " + grantUri + "; use startActivityAsCaller() instead");return -1;}