Android学习笔记（四）--Android4.4中获取资源路径问题，改进文件选择器。

    最近要做一个APP使用到文件选择，碰到4.4.2版本的手机就会出错，原来发现4.4获取资源路径已经改过了。

    关于Android4.4的图片路径获取，如果回来的Uri的格式有两种：

  Version 4.4.2 出现之前，Intent.ACTION_GET_CONTENT打开相册会返回如下形式的Uri :

  content://media/external/images/media/3951 ，

  使用ContentResolver查询MediaStore.Images.Media.DATA就可以找文件的URL, 然而在Google Nexus 7 上用同样的方法，却是返回如下Uri :

  content://com.android.providers.media.documents/document/image:3951，

综合网上的方法，下面是经过测试可以正常使用的文件选择器。

1.首先 需要添加权限。

<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>

2.showFileChooser函数

    private void showFileChooser(int file_code) {
        Intent intent = new Intent(Intent.ACTION_GET_CONTENT); 
//        Intent intent = new Intent(Intent.ACTION_OPEN_DOCUMENT);
//        Intent intent = new Intent(Intent.ACTION_PICK);

        intent.setType("image/*"); 
        intent.addCategory(Intent.CATEGORY_OPENABLE);
     
        try {
            startActivityForResult( Intent.createChooser(intent, "Select a File to Upload"), file_code);
        } catch (android.content.ActivityNotFoundException ex) {
            Toast.makeText(getActivity(), "Please install a File Manager.",  Toast.LENGTH_SHORT).show();
        }
    }

3.返回结果处理（由于项目需要 case比较多，根据实际需求来增减）

    public void onActivityResult(int requestCode, int resultCode, Intent data) {
           switch (requestCode) {
            case 0:      
            if (resultCode == Activity.RESULT_OK) {  
                Uri uri = data.getData();
                String path = FileUtils.getPath(getActivity().getApplicationContext(), uri);
                
                mTextViewMain.setText(path);
                mainurl=new File(path);
            }           
            break;
            
            case 1:      
            if (resultCode == Activity.RESULT_OK) {  
                // Get the Uri of the selected file 
                Uri uri = data.getData();
                String path = FileUtils.getPath(getActivity(), uri);
                mTextViewBody1.setText(path);
                body1=new File(path);
            }           
            break;
            
            case 2:      
            if (resultCode == Activity.RESULT_OK) {  
                // Get the Uri of the selected file 
                Uri uri = data.getData();
                String path = FileUtils.getPath(getActivity(), uri);
                mTextViewBody2.setText(path);
                body2=new File(path);
            }           
            break;
            
            case 3:      
            if (resultCode == Activity.RESULT_OK) {  
                // Get the Uri of the selected file 
                Uri uri = data.getData();
                String path = FileUtils.getPath(getActivity(), uri);
                mTextViewBody3.setText(path);
                body3=new File(path);
            }           
            break;
            
            case 4:      
            if (resultCode == Activity.RESULT_OK) {  
                // Get the Uri of the selected file 
                Uri uri = data.getData();
                String path = FileUtils.getPath(getActivity(), uri);
                mTextViewBody4.setText(path);
                body4=new File(path);
            }           
            break;
            
            
        }
    super.onActivityResult(requestCode, resultCode, data);        

        
    }
    

4.FileUtils类（转载于：http://stackoverflow.com/questions/20067508/get-real-path-from-uri-android-kitkat-new-storage-access-framework）

public class FileUtils {/**
     * Get a file path from a Uri. This will get the the path for Storage Access
     * Framework Documents, as well as the _data field for the MediaStore and
     * other file-based ContentProviders.
     *
     * @param context The context.
     * @param uri The Uri to query.
     * @author paulburke
     */
    public static String getPath(final Context context, final Uri uri) {

        final boolean isKitKat = Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT;

        // DocumentProvider
        if (isKitKat && DocumentsContract.isDocumentUri(context, uri)) {
            // ExternalStorageProvider
            if (isExternalStorageDocument(uri)) {
                final String docId = DocumentsContract.getDocumentId(uri);
                final String[] split = docId.split(":");
                final String type = split[0];

                if ("primary".equalsIgnoreCase(type)) {
                    return Environment.getExternalStorageDirectory() + "/" + split[1];
                }

                // TODO handle non-primary volumes
            }
            // DownloadsProvider
            else if (isDownloadsDocument(uri)) {

                final String id = DocumentsContract.getDocumentId(uri);
                final Uri contentUri = ContentUris.withAppendedId(
                        Uri.parse("content://downloads/public_downloads"), Long.valueOf(id));

                return getDataColumn(context, contentUri, null, null);
            }
            // MediaProvider
            else if (isMediaDocument(uri)) {
                final String docId = DocumentsContract.getDocumentId(uri);
                final String[] split = docId.split(":");
                final String type = split[0];

                Uri contentUri = null;
                if ("image".equals(type)) {
                    contentUri = MediaStore.Images.Media.EXTERNAL_CONTENT_URI;
                } else if ("video".equals(type)) {
                    contentUri = MediaStore.Video.Media.EXTERNAL_CONTENT_URI;
                } else if ("audio".equals(type)) {
                    contentUri = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;
                }

                final String selection = "_id=?";
                final String[] selectionArgs = new String[] {
                        split[1]
                };

                return getDataColumn(context, contentUri, selection, selectionArgs);
            }
        }
        // MediaStore (and general)
        else if ("content".equalsIgnoreCase(uri.getScheme())) {
            return getDataColumn(context, uri, null, null);
        }
        // File
        else if ("file".equalsIgnoreCase(uri.getScheme())) {
            return uri.getPath();
        }

        return null;
    }

    /**
     * Get the value of the data column for this Uri. This is useful for
     * MediaStore Uris, and other file-based ContentProviders.
     *
     * @param context The context.
     * @param uri The Uri to query.
     * @param selection (Optional) Filter used in the query.
     * @param selectionArgs (Optional) Selection arguments used in the query.
     * @return The value of the _data column, which is typically a file path.
     */
    public static String getDataColumn(Context context, Uri uri, String selection,
            String[] selectionArgs) {

        Cursor cursor = null;
        final String column = "_data";
        final String[] projection = {
                column
        };

        try {
            cursor = context.getContentResolver().query(uri, projection, selection, selectionArgs,
                    null);
            if (cursor != null && cursor.moveToFirst()) {
                final int column_index = cursor.getColumnIndexOrThrow(column);
                return cursor.getString(column_index);
            }
        } finally {
            if (cursor != null)
                cursor.close();
        }
        return null;
    }


    /**
     * @param uri The Uri to check.
     * @return Whether the Uri authority is ExternalStorageProvider.
     */
    public static boolean isExternalStorageDocument(Uri uri) {
        return "com.android.externalstorage.documents".equals(uri.getAuthority());
    }

    /**
     * @param uri The Uri to check.
     * @return Whether the Uri authority is DownloadsProvider.
     */
    public static boolean isDownloadsDocument(Uri uri) {
        return "com.android.providers.downloads.documents".equals(uri.getAuthority());
    }

    /**
     * @param uri The Uri to check.
     * @return Whether the Uri authority is MediaProvider.
     */
    public static boolean isMediaDocument(Uri uri) {
        return "com.android.providers.media.documents".equals(uri.getAuthority());
    }}