Android 4.4前后版本读取图库图片方式的变化
本文讲述Android 4.4（KitKat）前后访问图库以及访问后通过图片路径读取图片的变化
Android 4.4（KitKat）以前：
访问图库（方法一）：
/**
* Access the gallery to pick up an image.
*/
private void startPickPhotoActivity() {
Intent intent = new Intent(Intent. ACTION_GET_CONTENT );
intent.setType( "image/*" ); // Or 'image/ jpeg '
startActivityForResult(intent, RESULT_PICK_PHOTO_NORMAL );
}
访问图库（方法二）：
/**
* Access the gallery to pick up an image.
*/
private void startPickPhotoActivity() {
Intent intent = new Intent(Intent. ACTION_GET_CONTENT );
intent.setType( "image/*" ); // Or 'image/ jpeg '
Intent wrapperIntent = Intent. createChooser (intent, null );
startActivityForResult(wrapperIntent, RESULT_PICK_PHOTO_NORMAL );
}
获取文件路径&读取图片：
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
if (requestCode == RESULT_PICK_PHOTO_NORMAL) {
if (resultCode == RESULT_OK && data != null) {
mFileName = DemoUtils.getDataColumn(getApplicationContext(),
data.getData(), null, null);
mColorBitmap = DemoUtils.getBitmap(mFileName); mImage.setImageBitmap(mColorBitmap);
}
}
} public static final Bitmap getBitmap(String fileName) {
Bitmap bitmap = null;
try {
Options options = new Options();
options.inJustDecodeBounds = true;
BitmapFactory.decodeFile(fileName, options);
options.inSampleSize = Math.max(1, (int) Math.ceil(Math.max(
(double) options.outWidth / 1024f,
(double) options.outHeight / 1024f)));
options.inJustDecodeBounds = false;
bitmap = BitmapFactory.decodeFile(fileName, options);
} catch (OutOfMemoryError error) {
error.printStackTrace();
} return bitmap;
} /**
* 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 = MediaColumns.DATA;
final String[] projection = { column };
try {
cursor = context.getContentResolver().query(uri, projection,
selection, selectionArgs, null);
if (cursor != null && cursor.moveToFirst()) {
final int index = cursor.getColumnIndexOrThrow(column);
return cursor.getString(index);
}
} finally {
if (cursor != null)
cursor.close();
}
return null;
}
Android 4.4（KitKat）及以后：
访问图库（方法一）：同上方法一
访问图库（方法二）：同上方法二
访问图库（方法三）：
/**
* Access the gallery to pick up an image.
*/
@TargetApi (Build.VERSION_CODES. KITKAT )
private void startPickPhotoActivity() {
Intent intent = new Intent(Intent. ACTION_OPEN_DOCUMENT );
intent.setType( "image/*" ); // Or 'image/ jpeg '
startActivityForResult(intent, RESULT_PICK_PHOTO_NORMAL );
}
获取文件路径&读取图片：
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
if (requestCode == RESULT_PICK_PHOTO_KITKAT) {
if (resultCode == RESULT_OK && data != null) {
mFileName = DemoUtils.getPath(getApplicationContext(),
data.getData());
mColorBitmap = DemoUtils.getBitmap(mFileName); mImage.setImageBitmap(mColorBitmap);
}
}
} @TargetApi(Build.VERSION_CODES.KITKAT)
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 = MediaColumns._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;
} /**
* 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 = MediaColumns.DATA;
final String[] projection = { column };
try {
cursor = context.getContentResolver().query(uri, projection,
selection, selectionArgs, null);
if (cursor != null && cursor.moveToFirst()) {
final int index = cursor.getColumnIndexOrThrow(column);
return cursor.getString(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());
} /**
* @param uri
* The Uri to check.
* @return Whether the Uri authority is Google Photos.
*/
public static boolean isGooglePhotosUri(Uri uri) {
return "com.google.android.apps.photos.content".equals(uri
.getAuthority());
}
为什么会不一样呢？
Android 4.4（含）开始，通过方式访问图库后，返回的Uri如下（访问“最近”）：
Uri is： content://com.android.providers.media.documents/document/image%3A18838
Uri.getPath is ：/document/image:18838
对应的图片真实路径：/storage/emulated/0/Pictures/Screenshots/Screenshot_2014-09-22-21-40-53.png
不但如此，对于不同类型图库，返回的Uri形式并不相同（访问普通相册）：
Uri is： content://media/external/images/media/18822
Uri.getPath is ：/external/images/media/18822
对应的图片真实路径：/storage/emulated/0/Download/20130224235013.jpg
而4.4之前返回的Uri只存在一种形式，如下：
Uri is： content://media/external/images/media/14046
Uri.getPath is ：/external/images/media/14046
对应的图片真实路径：/storage/emulated/0/DCIM/Camera/20130224235013.jpg
因此，在Android 4.4或更高版本设备上，通过简单的getDataColumn(Context, Uri, null, null)进行图片数据库已经不能满足所有需求，因此在获取图片真实路径的时候需要根据不同类型区分对待。