android 7.0 应用间文件共享FileProvider

1.官方教程

　　Android 7.0 以后安全系数提高，应用间文件共享要使用FileProvider。原来的　file:/// Uri　替换为　content://Uri 

　　https://developer.android.com/reference/android/support/v4/content/FileProvider

2.步骤

1. Defining a FileProvider
2. Specifying Available Files
3. Retrieving the Content URI for a File
4. Granting Temporary Permissions to a URI
5. Serving a Content URI to Another App

3.示例

3.1 定义 FileProvider

　　在AndroidManifest.xml中

         <provider
             android:name="androidx.core.content.FileProvider"
             android:authorities="cn.com.txw.fileprovider"
             android:exported="false"
             android:grantUriPermissions="true">
             <meta-data
                 android:name="android.support.FILE_PROVIDER_PATHS"
                 android:resource="@xml/file_paths" />
         </provider>

　　非androidx 使用　android:name="android.support.v4.content.FileProvider"

3.2 定义共享文件的路径

 <?xml version="1.0" encoding="utf-8"?>
 <paths>
     <external-files-path    name="externalFiles"    path="download/"/>
     <external-path          name="externalRoot"     path="download/" />
     <root-path              name="root"             path="" />
 </paths>

注意　path的值是目录时要有　"/"　

<paths>可选子标签及含义 如下：

子标签	路径
file-path	Context.getFilesDir()
cache-path	getCacheDir()
external-path	Environment.getExternalStorageDirectory()
external-files-path	Context#getExternalFilesDir(String) Context.getExternalFilesDir(null).
external-cache-path	Context.getExternalCacheDir()
external-media-path	Context.getExternalMediaDirs()
root-path	根目录　"/"

3.3 生成共享文件的uri

  　　public static void openApkFile(String file ) {

         Intent intent = new Intent(Intent.ACTION_VIEW);
         intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
         Uri data;
         File apk = new File(file);

         if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
             final String author = "cn.com.txw.fileprovider";
             try {
                 data = FileProvider.getUriForFile(mContext, author, apk);
                 intent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION | Intent.FLAG_GRANT_WRITE_URI_PERMISSION);
             }catch (Exception e){
                 e.printStackTrace();
                 Log.e(TAG, "openApkFile: exception = " + e.getMessage() );
                 return;
             }
         } else {
             data = Uri.fromFile(apk);
         }
         intent.setDataAndType(data, "application/vnd.android.package-archive");
         mContext.startActivity(intent);
     }

FileProvider.getUriForFile(mContext, author, apk)　生成uri,其中：

• author　　　为AndroidManifest 中指定的　android:authorities="cn.com.txw.fileprovider"
• apk 　　　　为文件绝对路径
• mContext　 为Context

3.4 文件的临时权限

上述代码中的　intent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION | Intent.FLAG_GRANT_WRITE_URI_PERMISSION);　增加uri相关临时权限。

mContext.grantUriPermission开启权限

    uri = FileProvider.getUriForFile(mContext, author, apk);
    int mode_flags = Intent.FLAG_GRANT_READ_URI_PERMISSION | Intent.FLAG_GRANT_WRITE_URI_PERMISSION;
    mContext.grantUriPermission(mContext.getPackageName(), uri, mode_flags);
 　　intent.addFlags(mode_flags);

mContext.revokeUriPermission关闭权限

    mContext.revokeUriPermission(uri,mode_flags);

　

4.android 8.0的问题

　　上述示例是打开apk文件，注意在8.0后要申请”未知来源应用“的安装权限。

     private boolean checkPermissions(){
         if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.M) {
             String[] permissions = {
                     Manifest.permission.WRITE_EXTERNAL_STORAGE,
                     Manifest.permission.ACCESS_NETWORK_STATE,
                     Manifest.permission.REQUEST_INSTALL_PACKAGES};
             final int KG_PERMISSION = ;

             int permissionCheck =  ;

             for (String permission : permissions){
                 permissionCheck += checkSelfPermission(permission);
             }
             if (permissionCheck != PackageManager.PERMISSION_GRANTED) {
                 requestPermissions(permissions,KG_PERMISSION);
                 return false;
             }
         }
         return true;
     }