<!-- Base "touch slop" value used by ViewConfiguration as a movement threshold where scrolling should begin .--> <dimenname ="config_viewConfigurationTouchSlop">8dp</dimen>
/** * Set the scrolled position of your view. This will cause a call to * {@link #onScrollChanged(int, int, int, int)} and the view will be * invalidated. * * @param x the x position to scroll to * @param y the y position to scroll to */ publicvoidscrollTo(int x, int y) { if (mScrollX != x || mScrollY != y) { intoldX= mScrollX; intoldY= mScrollY; mScrollX = x; mScrollY = y; invalidateParentCaches(); onScrollChanged(mScrollX, mScrollY, oldX, oldY); if (!awakenScrollBars()) { postInvalidateOnAnimation(); } } }
/** * Move the scrolled position of your view. This will cause a call to * {@link #onScrollChanged(int, int, int, int)} and the view will be * invalidated. * * @param x the amount of pixels to scroll by horizontally * @param y the amount of pixels to scroll by vertically */ publicvoidscrollBy(int x, int y) { scrollTo(mScrollX + x, mScrollY + y); }
/** * Start scrolling by providing a starting point, the distance to travel, * and the duration of the scroll. * * @param startX Starting horizontal scroll offset in pixels. Positive * numbers will scroll the content to the left. * @param startY Starting vertical scroll offset in pixels. Positive numbers * will scroll the content up. * @param dx Horizontal distance to travel. Positive numbers will scroll the * content to the left. * @param dy Vertical distance to travel. Positive numbers will scroll the * content up. * @param duration Duration of the scroll in milliseconds. */ public void startScroll(int startX, int startY, int dx, int dy, int duration) { mMode = SCROLL_MODE; mFinished = false; mDuration = duration; mStartTime = AnimationUtils.currentAnimationTimeMillis(); mStartX = startX; mStartY = startY; mFinalX = startX + dx; mFinalY = startY + dy; mDeltaX = dx; mDeltaY = dy; mDurationReciprocal = 1.0f / (float) mDuration; }
/** * Call this when you want to know the new location. If it returns true, * the animation is not yet finished. */ publicbooleancomputeScrollOffset() { ... inttimePassed= (int)(AnimationUtils.currentAnimationTimeMillis() - mStartTime);
switch (event.getAction()){ case MotionEvent.ACTION_DOWN:{ parent.requestDisallowInterceptTouchEvent(true); break; } case MotionEvent.ACTION_MOVE:{ intdeltaX= x - mLastX; intdeltaY= y - mLastY; if(父容器需要此类点击事件){ parent.requestDisallowInterceptTouchEvent(false) }
break; } case MotionEvent.ACTION_UP:{ break; } default: break;
/* COMPLETED (1) Add content provider constants to the Contract Clients need to know how to access the task data, and it's your job to provide these content URI's for the path to that data: 1) Content authority, 2) Base content URI, 3) Path(s) to the tasks directory 4) Content URI for data in the TaskEntry class */
// The authority, which is how your code knows which Content Provider to access publicstaticfinalStringAUTHORITY="com.example.android.todolist";
// The base content URI = "content://" + <authority> publicstaticfinalUriBASE_CONTENT_URI= Uri.parse("content://" + AUTHORITY);
// Define the possible paths for accessing data in this contract // This is the path for the "tasks" directory publicstaticfinalStringPATH_TASKS="tasks";
/* TaskEntry is an inner class that defines the contents of the task table */ publicstaticfinalclassTaskEntryimplementsBaseColumns {
// TaskEntry content URI = base content URI + path publicstaticfinalUriCONTENT_URI= BASE_CONTENT_URI.buildUpon().appendPath(PATH_TASKS).build();
// Verify that TaskContentProvider extends from ContentProvider and implements required methods publicclassTaskContentProviderextendsContentProvider {
// COMPLETED (1) Define final integer constants for the directory of tasks and a single item. // It's convention to use 100, 200, 300, etc for directories, // and related ints (101, 102, ..) for items in that directory. publicstaticfinalintTASKS=100; publicstaticfinalintTASK_WITH_ID=101;
// COMPLETED (3) Declare a static variable for the Uri matcher that you construct privatestaticfinalUriMatchersUriMatcher= buildUriMatcher();
// COMPLETED (2) Define a static buildUriMatcher method that associates URI's with their int match /** Initialize a new matcher object without any matches, then use .addURI(String authority, String path, int match) to add matches */ publicstatic UriMatcher buildUriMatcher() {
// Initialize a UriMatcher with no matches by passing in NO_MATCH to the constructor UriMatcheruriMatcher=newUriMatcher(UriMatcher.NO_MATCH);
/* All paths added to the UriMatcher have a corresponding int. For each kind of uri you may want to access, add the corresponding match with addURI. The two calls below add matches for the task directory and a single item by ID. */ uriMatcher.addURI(TaskContract.AUTHORITY, TaskContract.PATH_TASKS, TASKS); uriMatcher.addURI(TaskContract.AUTHORITY, TaskContract.PATH_TASKS + "/#", TASK_WITH_ID);
return uriMatcher; }
// Member variable for a TaskDbHelper that's initialized in the onCreate() method private TaskDbHelper mTaskDbHelper;
/* onCreate() is where you should initialize anything you’ll need to setup your underlying data source. In this case, you’re working with a SQLite database, so you’ll need to initialize a DbHelper to gain access to it. */ @Override publicbooleanonCreate() { // Complete onCreate() and initialize a TaskDbhelper on startup // [Hint] Declare the DbHelper as a global variable
// Implement insert to handle requests to insert a single new row of data @Override public Uri insert(@NonNull Uri uri, ContentValues values) { // Get access to the task database (to write new data to) finalSQLiteDatabasedb= mTaskDbHelper.getWritableDatabase();
// Write URI matching code to identify the match for the tasks directory intmatch= sUriMatcher.match(uri); Uri returnUri; // URI to be returned
switch (match) { case TASKS: // Insert new values into the database // Inserting values into tasks table longid= db.insert(TABLE_NAME, null, values); if ( id > 0 ) { returnUri = ContentUris.withAppendedId(TaskContract.TaskEntry.CONTENT_URI, id); } else { thrownewandroid.database.SQLException("Failed to insert row into " + uri); } break; // Set the value for the returnedUri and write the default case for unknown URI's // Default case throws an UnsupportedOperationException default: thrownewUnsupportedOperationException("Unknown uri: " + uri); }
// Notify the resolver if the uri has been changed, and return the newly inserted URI getContext().getContentResolver().notifyChange(uri, null);
// Return constructed uri (this points to the newly inserted row of data) return returnUri; }
// Implement query to handle requests for data by URI @Override public Cursor query(@NonNull Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {
// Get access to underlying database (read-only for query) finalSQLiteDatabasedb= mTaskDbHelper.getReadableDatabase();
// Write URI match code // Write a query for the tasks directory and default case
switch (match) { // Query for the tasks directory case TASKS: retCursor = db.query(TABLE_NAME, projection, selection, selectionArgs, null, null, sortOrder); break;
// Add a case to query for a single row of data by ID // Use selections and selectionArgs to filter for that ID case TASK_WITH_ID: // Get the id from the URI Stringid= uri.getPathSegments().get(1);
// Selection is the _ID column = ?, and the Selection args = the row ID from the URI StringmSelection="_id=?"; String[] mSelectionArgs = newString[]{id};
// Construct a query as you would normally, passing in the selection/args retCursor = db.query(TABLE_NAME, projection, mSelection, mSelectionArgs, null, null, sortOrder); break;
// Update won't be used in the final ToDoList app but is implemented here for completeness // This updates a single item (by it's ID) in the tasks directory @Override publicintupdate(@NonNull Uri uri, ContentValues values, String selection, String[] selectionArgs) {
//Keep track of if an update occurs int tasksUpdated;
// match code intmatch= sUriMatcher.match(uri);
switch (match) { case TASK_WITH_ID: //update a single task by getting the id Stringid= uri.getPathSegments().get(1); //using selections tasksUpdated = mTaskDbHelper.getWritableDatabase().update(TABLE_NAME, values, "_id=?", newString[]{id}); break; default: thrownewUnsupportedOperationException("Unknown uri: " + uri); }
if (tasksUpdated != 0) { //set notifications if a task was updated getContext().getContentResolver().notifyChange(uri, null); }
// return number of tasks updated return tasksUpdated; }
// Implement delete to delete a single row of data @Override publicintdelete(@NonNull Uri uri, String selection, String[] selectionArgs) {
// Get access to the database and write URI matching code to recognize a single item finalSQLiteDatabasedb= mTaskDbHelper.getWritableDatabase();
intmatch= sUriMatcher.match(uri); // Keep track of the number of deleted tasks int tasksDeleted; // starts as 0
// Write the code to delete a single row of data // [Hint] Use selections to delete an item by its row ID switch (match) { // Handle the single item case, recognized by the ID included in the URI path case TASK_WITH_ID: // Get the task ID from the URI path Stringid= uri.getPathSegments().get(1); // Use selections/selectionArgs to filter for this ID tasksDeleted = db.delete(TABLE_NAME, "_id=?", newString[]{id}); break; default: thrownewUnsupportedOperationException("Unknown uri: " + uri); }
// Notify the resolver of a change and return the number of items deleted if (tasksDeleted != 0) { // A task was deleted, set notification getContext().getContentResolver().notifyChange(uri, null); }
// Return the number of tasks deleted return tasksDeleted; }
/* getType() handles requests for the MIME type of data We are working with two types of data: 1) a directory and 2) a single row of data. This method will not be used in our app, but gives a way to standardize the data formats that your provider accesses, and this can be useful for data organization. For now, this method will not be used but will be provided for completeness. */ @Override public String getType(@NonNull Uri uri) { intmatch= sUriMatcher.match(uri);
switch (match) { case TASKS: // directory return"vnd.android.cursor.dir" + "/" + TaskContract.AUTHORITY + "/" + TaskContract.PATH_TASKS; case TASK_WITH_ID: // single item type return"vnd.android.cursor.item" + "/" + TaskContract.AUTHORITY + "/" + TaskContract.PATH_TASKS; default: thrownewUnsupportedOperationException("Unknown uri: " + uri); } }