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 = 13440;

            int permissionCheck = 0 ;

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