2016-05-26
9:42 AM
有時使用檔案選擇器取得路徑時會發現路徑是奇怪的 content://downloads/public_downloads 字串
而這種路徑使用 context.getContentResolver().query(); 方法取得的路徑會是空的
其實是因為新版 Android 在路徑上是使用 uri 的方式表示的
有點像網址，好處是同一個 uri 可以指定到不同的實體路徑內
用以對應不同的開發商與使用者設定
壞處就是取得路徑的方法變得較麻煩(而且官方文件似乎找不到方法? WTF?)
而且很多類型的檔案取得路徑的方式也沒有統一
以下就是對應各版本(4.4 以上)取得路徑的 FileUtil 的原始碼
檔案瀏覽器的使用方式可以到 啟動檔案瀏覽器選擇檔案 教學查看
程式碼範例
import android.content.ContentUris;
import android.content.Context;
import android.database.Cursor;
import android.net.Uri;
import android.os.Environment;
import android.provider.DocumentsContract;
import android.provider.MediaStore;
import cmc.toolkit.FileKit;
import com.ihad.ptt.model.exception.EmptyFilePathException;
import com.ihad.ptt.model.exception.IllegalTrueTypeFontException;
import java.io.File;
import java.io.FileNotFoundException;
public class FileUtils {
/**
* 從 uri 取得檔案路徑 這將從 Storage Access Framework Documents 取得路徑
* 也會使用從 _data 欄位取得 MediaStore 以及其他 file-based ContentProviders 的對應路徑
*
* @param context The context.
* @param uri The Uri to query.
* @author paulburke
*/
public static String getPath(final Context context, final Uri uri) {
// DocumentProvider
if ( 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)) {
String path = Environment.getExternalStorageDirectory().getPath();
if (split.length > 1) {
path += "/" + split[1];
}
return path;
}
else {
String path;
if (Environment.isExternalStorageRemovable()) {
path = System.getenv("EXTERNAL_STORAGE");
} else {
path = System.getenv("SECONDARY_STORAGE");
if (path == null || path.length() == 0) {
path = System.getenv("EXTERNAL_SDCARD_STORAGE");
}
}
if (split.length > 1) {
path += "/" + split[1];
}
return path;
}
}
// 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 the remote address
if (isGooglePhotosUri(uri)) return uri.getLastPathSegment();
return getDataColumn(context, uri, null, null);
}
// File
else if ("file".equalsIgnoreCase(uri.getScheme())) {
return uri.getPath();
}
return null;
}
/**
* 從 data 欄位取得 uri 對應的實體路徑
* 主要用以取得 MediaStore Uris 以及其他 file-based ContentProviders 的對應路徑
*
* @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.
* @author paulburke
*/
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 是否為 ExternalStorageProvider 類型的 uri
* @author paulburke
*/
public static boolean isExternalStorageDocument(Uri uri) {
return "com.android.externalstorage.documents".equals(uri.getAuthority());
}
/**
* @param uri The Uri to check.
* @return 是否為 DownloadsProvider 類型的 uri
* @author paulburke
*/
public static boolean isDownloadsDocument(Uri uri) {
return "com.android.providers.downloads.documents".equals(uri.getAuthority());
}
/**
* @param uri The Uri to check.
* @return MediaProvider 類型的 uri
* @author paulburke
*/
public static boolean isMediaDocument(Uri uri) {
return "com.android.providers.media.documents".equals(uri.getAuthority());
}
/**
* @param uri The Uri to check.
* @return 是否為 Google Photos 類型的 uri
*/
public static boolean isGooglePhotosUri(Uri uri) {
return "com.google.android.apps.photos.content".equals(uri.getAuthority());
}
// 檢查檔案類型的小範例
/**
* 檢查取回的檔案副檔名
* @param path 檔案路徑
* @return
* 若檔案類型正確則回傳檔案名稱, 反之則回傳空字串
* @throws EmptyFilePathException 路徑是空字串或是 null 物件
* @throws FileNotFoundException 檔案不存在
* @throws IllegalTrueTypeFontException 檔案類型不正確
*/
public static String typefaceChecker(String path) throws EmptyFilePathException, FileNotFoundException, IllegalTrueTypeFontException {
if( path == null || path.isEmpty() ){
throw new EmptyFilePathException( "File path is empty" );
}
File file = new File(path);
if( !file.exists() || !file.isFile() ) {
throw new FileNotFoundException( "File path : " + path );
}
String filename = file.getName();
String ext = FileKit.getFileExt(filename);
if( !ext.equalsIgnoreCase(".ttf") ){
throw new IllegalTrueTypeFontException( "File path : " + path + ", File name : " + filename + ", ext : " + ext );
}
return filename;
}
}
各項資料連結
啟動檔案瀏覽器選擇檔案
Stackoverflow - Get real path from URI, Android KitKat new storage access framework
GitHub - aFileChooser
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