java.lang.Object | |
↳ | android.content.ClipData |
Representation of a clipped data on the clipboard.
ClippedData is a complex type containing one or Item instances, each of which can hold one or more representations of an item of data. For display to the user, it also has a label and iconic representation.
A ClipData contains a ClipDescription
, which describes
important meta-data about the clip. In particular, its
getDescription().getMimeType(int)
must return correct MIME type(s) describing the data in the clip. For help
in correctly constructing a clip with the correct MIME type, use
newPlainText(CharSequence, CharSequence)
,
newUri(ContentResolver, CharSequence, Uri)
, and
newIntent(CharSequence, Intent)
.
Each Item instance can be one of three main classes of data: a simple
CharSequence of text, a single Intent object, or a Uri. See ClipData.Item
for more details.
For more information about using the clipboard framework, read the Copy and Paste developer guide.
To implement a paste or drop of a ClippedData object into an application,
the application must correctly interpret the data for its use. If the ClipData.Item
it contains is simple text or an Intent, there is little to be done: text
can only be interpreted as text, and an Intent will typically be used for
creating shortcuts (such as placing icons on the home screen) or other
actions.
If all you want is the textual representation of the clipped data, you
can use the convenience method Item.coerceToText
.
In this case there is generally no need to worry about the MIME types
reported by getDescription().getMimeType(int)
,
since any clip item an always be converted to a string.
More complicated exchanges will be done through URIs, in particular
"content:" URIs. A content URI allows the recipient of a ClippedData item
to interact closely with the ContentProvider holding the data in order to
negotiate the transfer of that data. The clip must also be filled in with
the available MIME types; newUri(ContentResolver, CharSequence, Uri)
will take care of correctly doing this.
For example, here is the paste function of a simple NotePad application. When retrieving the data from the clipboard, it can do either two things: if the clipboard contains a URI reference to an existing note, it copies the entire structure of the note into a new note; otherwise, it simply coerces the clip into text and uses that as the new note's contents.
/** * A helper method that replaces the note's data with the contents of the clipboard. */ private final void performPaste() { // Gets a handle to the Clipboard Manager ClipboardManager clipboard = (ClipboardManager) getSystemService(Context.CLIPBOARD_SERVICE); // Gets a content resolver instance ContentResolver cr = getContentResolver(); // Gets the clipboard data from the clipboard ClipData clip = clipboard.getPrimaryClip(); if (clip != null) { String text=null; String title=null; // Gets the first item from the clipboard data ClipData.Item item = clip.getItemAt(0); // Tries to get the item's contents as a URI pointing to a note Uri uri = item.getUri(); // Tests to see that the item actually is an URI, and that the URI // is a content URI pointing to a provider whose MIME type is the same // as the MIME type supported by the Note pad provider. if (uri != null && NotePad.Notes.CONTENT_ITEM_TYPE.equals(cr.getType(uri))) { // The clipboard holds a reference to data with a note MIME type. This copies it. Cursor orig = cr.query( uri, // URI for the content provider PROJECTION, // Get the columns referred to in the projection null, // No selection variables null, // No selection variables, so no criteria are needed null // Use the default sort order ); // If the Cursor is not null, and it contains at least one record // (moveToFirst() returns true), then this gets the note data from it. if (orig != null) { if (orig.moveToFirst()) { int colNoteIndex = mCursor.getColumnIndex(NotePad.Notes.COLUMN_NAME_NOTE); int colTitleIndex = mCursor.getColumnIndex(NotePad.Notes.COLUMN_NAME_TITLE); text = orig.getString(colNoteIndex); title = orig.getString(colTitleIndex); } // Closes the cursor. orig.close(); } } // If the contents of the clipboard wasn't a reference to a note, then // this converts whatever it is to text. if (text == null) { text = item.coerceToText(this).toString(); } // Updates the current note with the retrieved title and text. updateNote(text, title); } }
In many cases an application can paste various types of streams of data. For
example, an e-mail application may want to allow the user to paste an image
or other binary data as an attachment. This is accomplished through the
ContentResolver getStreamTypes(Uri, String)
and
openTypedAssetFileDescriptor(Uri, String, android.os.Bundle)
methods. These allow a client to discover the type(s) of data that a particular
content URI can make available as a stream and retrieve the stream of data.
For example, the implementation of Item.coerceToText
itself uses this to try to retrieve a URI clip as a stream of text:
public CharSequence coerceToText(Context context) { // If this Item has an explicit textual value, simply return that. CharSequence text = getText(); if (text != null) { return text; } // If this Item has a URI value, try using that. Uri uri = getUri(); if (uri != null) { // First see if the URI can be opened as a plain text stream // (of any sub-type). If so, this is the best textual // representation for it. FileInputStream stream = null; try { // Ask for a stream of the desired type. AssetFileDescriptor descr = context.getContentResolver() .openTypedAssetFileDescriptor(uri, "text/*", null); stream = descr.createInputStream(); InputStreamReader reader = new InputStreamReader(stream, "UTF-8"); // Got it... copy the stream into a local string and return it. StringBuilder builder = new StringBuilder(128); char[] buffer = new char[8192]; int len; while ((len=reader.read(buffer)) > 0) { builder.append(buffer, 0, len); } return builder.toString(); } catch (FileNotFoundException e) { // Unable to open content URI as text... not really an // error, just something to ignore. } catch (IOException e) { // Something bad has happened. Log.w("ClippedData", "Failure loading text", e); return e.toString(); } finally { if (stream != null) { try { stream.close(); } catch (IOException e) { } } } // If we couldn't open the URI as a stream, then the URI itself // probably serves fairly well as a textual representation. return uri.toString(); } // Finally, if all we have is an Intent, then we can just turn that // into text. Not the most user-friendly thing, but it's something. Intent intent = getIntent(); if (intent != null) { return intent.toUri(Intent.URI_INTENT_SCHEME); } // Shouldn't get here, but just in case... return ""; }
To be the source of a clip, the application must construct a ClippedData
object that any recipient can interpret best for their context. If the clip
is to contain a simple text, Intent, or URI, this is easy: an ClipData.Item
containing the appropriate data type can be constructed and used.
More complicated data types require the implementation of support in a ContentProvider for describing and generating the data for the recipient. A common scenario is one where an application places on the clipboard the content: URI of an object that the user has copied, with the data at that URI consisting of a complicated structure that only other applications with direct knowledge of the structure can use.
For applications that do not have intrinsic knowledge of the data structure,
the content provider holding it can make the data available as an arbitrary
number of types of data streams. This is done by implementing the
ContentProvider getStreamTypes(Uri, String)
and
openTypedAssetFile(Uri, String, android.os.Bundle)
methods.
Going back to our simple NotePad application, this is the implementation it may have to convert a single note URI (consisting of a title and the note text) into a stream of plain text data.
/** * This describes the MIME types that are supported for opening a note * URI as a stream. */ static ClipDescription NOTE_STREAM_TYPES = new ClipDescription(null, new String[] { ClipDescription.MIMETYPE_TEXT_PLAIN }); /** * Returns the types of available data streams. URIs to specific notes are supported. * The application can convert such a note to a plain text stream. * * @param uri the URI to analyze * @param mimeTypeFilter The MIME type to check for. This method only returns a data stream * type for MIME types that match the filter. Currently, only text/plain MIME types match. * @return a data stream MIME type. Currently, only text/plan is returned. * @throws IllegalArgumentException if the URI pattern doesn't match any supported patterns. */ @Override public String[] getStreamTypes(Uri uri, String mimeTypeFilter) { /** * Chooses the data stream type based on the incoming URI pattern. */ switch (sUriMatcher.match(uri)) { // If the pattern is for notes or live folders, return null. Data streams are not // supported for this type of URI. case NOTES: case LIVE_FOLDER_NOTES: return null; // If the pattern is for note IDs and the MIME filter is text/plain, then return // text/plain case NOTE_ID: return NOTE_STREAM_TYPES.filterMimeTypes(mimeTypeFilter); // If the URI pattern doesn't match any permitted patterns, throws an exception. default: throw new IllegalArgumentException("Unknown URI " + uri); } } /** * Returns a stream of data for each supported stream type. This method does a query on the * incoming URI, then uses * {@link android.content.ContentProvider#openPipeHelper(Uri, String, Bundle, Object, * PipeDataWriter)} to start another thread in which to convert the data into a stream. * * @param uri The URI pattern that points to the data stream * @param mimeTypeFilter A String containing a MIME type. This method tries to get a stream of * data with this MIME type. * @param opts Additional options supplied by the caller. Can be interpreted as * desired by the content provider. * @return AssetFileDescriptor A handle to the file. * @throws FileNotFoundException if there is no file associated with the incoming URI. */ @Override public AssetFileDescriptor openTypedAssetFile(Uri uri, String mimeTypeFilter, Bundle opts) throws FileNotFoundException { // Checks to see if the MIME type filter matches a supported MIME type. String[] mimeTypes = getStreamTypes(uri, mimeTypeFilter); // If the MIME type is supported if (mimeTypes != null) { // Retrieves the note for this URI. Uses the query method defined for this provider, // rather than using the database query method. Cursor c = query( uri, // The URI of a note READ_NOTE_PROJECTION, // Gets a projection containing the note's ID, title, // and contents null, // No WHERE clause, get all matching records null, // Since there is no WHERE clause, no selection criteria null // Use the default sort order (modification date, // descending ); // If the query fails or the cursor is empty, stop if (c == null || !c.moveToFirst()) { // If the cursor is empty, simply close the cursor and return if (c != null) { c.close(); } // If the cursor is null, throw an exception throw new FileNotFoundException("Unable to query " + uri); } // Start a new thread that pipes the stream data back to the caller. return new AssetFileDescriptor( openPipeHelper(uri, mimeTypes[0], opts, c, this), 0, AssetFileDescriptor.UNKNOWN_LENGTH); } // If the MIME type is not supported, return a read-only handle to the file. return super.openTypedAssetFile(uri, mimeTypeFilter, opts); } /** * Implementation of {@link android.content.ContentProvider.PipeDataWriter} * to perform the actual work of converting the data in one of cursors to a * stream of data for the client to read. */ @Override public void writeDataToPipe(ParcelFileDescriptor output, Uri uri, String mimeType, Bundle opts, Cursor c) { // We currently only support conversion-to-text from a single note entry, // so no need for cursor data type checking here. FileOutputStream fout = new FileOutputStream(output.getFileDescriptor()); PrintWriter pw = null; try { pw = new PrintWriter(new OutputStreamWriter(fout, "UTF-8")); pw.println(c.getString(READ_NOTE_TITLE_INDEX)); pw.println(""); pw.println(c.getString(READ_NOTE_NOTE_INDEX)); } catch (UnsupportedEncodingException e) { Log.w(TAG, "Ooops", e); } finally { c.close(); if (pw != null) { pw.flush(); } try { fout.close(); } catch (IOException e) { } } }
The copy operation in our NotePad application is now just a simple matter of making a clip containing the URI of the note being copied:
case R.id.context_copy: // Gets a handle to the clipboard service. ClipboardManager clipboard = (ClipboardManager) getSystemService(Context.CLIPBOARD_SERVICE); // Copies the notes URI to the clipboard. In effect, this copies the note itself clipboard.setPrimaryClip(ClipData.newUri( // new clipboard item holding a URI getContentResolver(), // resolver to retrieve URI info "Note", // label for the clip noteUri) // the URI ); // Returns to the caller and skips further processing. return true;
Note if a paste operation needs this clip as text (for example to paste
into an editor), then coerceToText(Context)
will ask the content
provider for the clip URI as text and successfully paste the entire note.
Nested Classes | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
ClipData.Item | Description of a single item in a ClippedData. |
[Expand]
Inherited Constants | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
From interface
android.os.Parcelable
|
Fields | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
CREATOR |
Public Constructors | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
Create a new clip.
| |||||||||||
Create a new clip.
| |||||||||||
Create a new clip that is a copy of another clip.
|
Public Methods | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
Add a new Item to the overall ClipData container.
| |||||||||||
Describe the kinds of special objects contained in this Parcelable's
marshalled representation.
| |||||||||||
Return the
ClipDescription associated with this data, describing
what it contains. | |||||||||||
Return a single item inside of the clip data.
| |||||||||||
Return the number of items in the clip data.
| |||||||||||
Create a new ClipData holding data of the type
MIMETYPE_TEXT_HTML . | |||||||||||
Create a new ClipData holding an Intent with MIME type
MIMETYPE_TEXT_INTENT . | |||||||||||
Create a new ClipData holding data of the type
MIMETYPE_TEXT_PLAIN . | |||||||||||
Create a new ClipData holding an URI with MIME type
MIMETYPE_TEXT_URILIST . | |||||||||||
Create a new ClipData holding a URI.
| |||||||||||
Returns a string containing a concise, human-readable description of this
object.
| |||||||||||
Flatten this object in to a Parcel.
|
[Expand]
Inherited Methods | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
From class
java.lang.Object
| |||||||||||
From interface
android.os.Parcelable
|
Create a new clip.
label | Label to show to the user describing this clip. |
---|---|
mimeTypes | An array of MIME types this data is available as. |
item | The contents of the first item in the clip. |
Create a new clip.
description | The ClipDescription describing the clip contents. |
---|---|
item | The contents of the first item in the clip. |
Create a new clip that is a copy of another clip. This does a deep-copy of all items in the clip.
other | The existing ClipData that is to be copied. |
---|
Add a new Item to the overall ClipData container.
Describe the kinds of special objects contained in this Parcelable's marshalled representation.
Return the ClipDescription
associated with this data, describing
what it contains.
Return a single item inside of the clip data. The index can range
from 0 to getItemCount()
-1.
Create a new ClipData holding data of the type
MIMETYPE_TEXT_HTML
.
label | User-visible label for the clip data. |
---|---|
text | The text of clip as plain text, for receivers that don't handle HTML. This is required. |
htmlText | The actual HTML text in the clip. |
Create a new ClipData holding an Intent with MIME type
MIMETYPE_TEXT_INTENT
.
label | User-visible label for the clip data. |
---|---|
intent | The actual Intent in the clip. |
Create a new ClipData holding data of the type
MIMETYPE_TEXT_PLAIN
.
label | User-visible label for the clip data. |
---|---|
text | The actual text in the clip. |
Create a new ClipData holding an URI with MIME type
MIMETYPE_TEXT_URILIST
.
Unlike newUri(ContentResolver, CharSequence, Uri)
, nothing
is inferred about the URI -- if it is a content: URI holding a bitmap,
the reported type will still be uri-list. Use this with care!
label | User-visible label for the clip data. |
---|---|
uri | The URI in the clip. |
Create a new ClipData holding a URI. If the URI is a content: URI,
this will query the content provider for the MIME type of its data and
use that as the MIME type. Otherwise, it will use the MIME type
MIMETYPE_TEXT_URILIST
.
resolver | ContentResolver used to get information about the URI. |
---|---|
label | User-visible label for the clip data. |
uri | The URI in the clip. |
Returns a string containing a concise, human-readable description of this object. Subclasses are encouraged to override this method and provide an implementation that takes into account the object's type and data. The default implementation is equivalent to the following expression:
getClass().getName() + '@' + Integer.toHexString(hashCode())
See Writing a useful
toString
method
if you intend implementing your own toString
method.
Flatten this object in to a Parcel.
dest | The Parcel in which the object should be written. |
---|---|
flags | Additional flags about how the object should be written.
May be 0 or PARCELABLE_WRITE_RETURN_VALUE .
|