I have a simple draw application on Canvas. User should be able to draw with a chosen color. On MotionEvent.ACTION_UP, invalidate() is called. Now it redraws previously drawn lines with the current color ( Redrawing the entire drawing with the current color). I do not want to change the color of previously drawn lines. I am not sure what is missing. Can I make it redraw only newly drawn lines?
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The green plane is shown on the golden-brown surface but when I press a key nothing happens. I want eventually be able to move the plane pressing 4 different keys + another one for shooting but that's easy if I can just get the thing moving in the first place. When I press a key in the emulator, nothing happens at all.
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I am new to Android development, just reading docs and trying the APIs. I am quit confused how ImageView managed to draw just a part of its content after an invalidate(Rect) invocation.
I've checked ImageView.java, found no other drawing method except onDraw(Canvas), but onDraw(Canvas) only cut the drawable only if it is beyound the view's visible boundary. I also read the implementation of View.invalidate(Rect), I think the key of this function is calling to mParent.invalidateChild(this, r);
However, I think the parent view doesn't know how to draw the child in the given Rect, it finally has to call some method of it child to paint out. Has anybody investigated this part of codes? Would you please give me some guide?
What's the functional difference between these list view methods: invalidate() and invalidate Views() ? Which one is faster to refresh a list view?
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View 5 Replies View RelatedI'm using a class extends with view. I'm using timer in that class. I'm using onTouchEvent() also. I onTouchEvent() I'm using invalidate(). So it is calling onDraw(). When i use invalidate() in Timer. It is not calling onDraw().
View 8 Replies View RelatedI hope this question belongs in the Android Developers and not Android Beginners group but I have a question about ScrollViews. I am currently working with a customized GraphView class and am trying to put it into a ScrollView but it doesn't seem to work. Whenever I run the code, it comes up with a blank screen. I've written the code in XML and also tried to create the ScrollView encapsulating the GraphView programmatically but whenever the code runs, it comes up with just a blank screen and GraphView's onDraw() is never called.Code...
View 2 Replies View RelatedI have an List Activity with a Base Adapter where the contents have changed (example - the rows are reordered). I have tried invalidate.
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I am new to Android. Can someone show to me how do I force invalidate a portion of an item in listview? I have listview row item that contains textview and image view. I only want to invalidate text in the textview of a particular item in the listview.
View 3 Replies View RelatedI am trying to draw an animation. To do so I have extended View and overridden the onDraw() method. What I would expect is that each time onDraw() is called the canvas would be in the state that I left it in and I could choose to clear it or just draw over parts of it (This is how it worked when I used a SurfaceView) but each time the canvas comes back already cleared. Is there a way that I can not have it cleared? Or maybe save the previous state into a Bitmap so I can just draw that Bitmap and then draw over top of it?
View 4 Replies View RelatedI can add children just fine, but I'm never getting my custom onDraw() being called. dispatchDraw() gets called, but that seems to have a different canvas (the one that's within the padding. I need to draw on the whole layout area). Is there some flag that needs to get set to get onDraw() called for the layout?
View 1 Replies View RelatedI have a ListView with an adapter attached. In the individual list items are placed views with widgets that continually update themselves within the list. Everything works well except for this case: Touch the list and start scrolling it just before the longTouch event would be thrown. Then lift your finger from the ListView. At this point the widget views in the ListView no longer receive onDraw events in response to the invalidate calls that continue to be made on the ListView. It is like the ListView starting blocking the invalidate calls during the scroll and forgot to re-allow them when the scrolling stopped. If I touch and scroll with out holding or scroll with a fling this does not happen. The ListView will start allowing the onDraw events back through if you touch anywhere in the list. Any ideas on how to help the ListView not block those onDraw calls?
View 3 Replies View RelatedWe came across a strange behavior. The clip rect of our custom view is getting reset to its entire visible region, if we change the value of another view.
View 4 Replies View Relatedwhat parameters do I pass to this function? invalidate(left, top, right, bottom) for use with google map on android ?
View 1 Replies View RelatedI have an expandable list view with a static array for the group data and an SQLite database for the child data. It is implemented with the BaseExpandableListAdapter and works great, except, when I edit the database to delete or add children to the list I do not see the changes onscreen. It looks like I can use the registerDataSetObserver method to notify the adapter and expandable list of a data change. What I have to do in the callback to make Android redraw the list after data changes is what I need to know. Can I do it? Documentation on this part of the SDK is a bit sparse and expandable list view example code is not a good match. Can anyone offer advice on how to use a DataSetObserver? It feels like I have to switch over to a Cursor type adapter.
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View 1 Replies View RelatedI'm implementing a fairly standard app with the Android sdk that involves drawing using the SurfaceView, SurfaceHolder, Callback setup.
In my main thread (UI thread) I have no drawing or handling of the SurfaceHolder (or the canvas you retrieve with it).
In a separate thread I have the following:
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This code is being executed, throws no exceptions, and has no negative side effects that I can find; however, the unlockCanvasAndPost() call never causes onDraw() to be called.
In other words, unlockCanvasAndPost() does not cause a redraw of the SurfaceView.
Any ideas what could cause this symptom? I have plenty of java experience, a fair amount of android experience, and a lot of debugging experience and cannot track this one down.
I have create a subclass of View and overwritten onDraw() - see some test code below. It draws a line consisting of some points. Before the line is drawn the canvas is rotated and restore after the drawing. The angle by which the canvas is rotated increases by 5 degrees every time onDraw() is called. The view is invalidated about once a second causing the view to be redrawn. Due to the rotated canvas the line drawn looks like a clock hand rotating counter-clockwise. This works - but not always. Sometimes the line is not drawn for one or more seconds, although I know from the log statement that onDraw() was called. Sometimes means: The line may be not shown after 8 seconds, then again after 35 seconds and so on. If the canvas is not rotated the problem does not occur. This also happens when I use a SurfaceView instead of a View. It does not only occur in the simulator but also on my G1 - both using Android 1.6.
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I want to get a set of Views to redraw after I change some drawing parameters. I'm calling invalidate() and forceLayout() on the parent of the Views but nothing happens. If I rotate the screen then the Views redraw correctly using the new parameters, as you would expect. What else do I need to do to get the Views to redraw?
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View 4 Replies View RelatedI have a custom view that fills my entire screen. (A piano keyboard) When a user touches the key, it causes invalidate() to be called and the whole keyboard gets redrawn to show the new state with a touched key.
Currently the view is very simple, but I plan to add a bit more nice graphics. Since the whole keyboard is dynamically rendered this would make redrawing the entire keyboard more expensive.
So I thought, let's look into partial redrawing. Now I call invalidate(Rect dirty) with the correct dirty region. I set my onDraw(Canvas canvas) method to only draw the keys in the dirty region if I do indeed want a partial redraw. This results in those keys being drawn, but the rest of the keyboard is totally black/not drawn at all.
Am I wrong in expecting that calling invalidate(Rect dirty) would "cache" the current canvas, and only "allows" drawing in the dirty region?
Is there any way I can achieve what I want? (A way to "cache" the canvas and only redraw the dirty area?"
I have just published my application and would to be able to provide a link on my website that will show my application? Also, if they browse to my website on their phone, is there some kind of link I can add that the user can click on that will take them to the market to download my app?
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View 6 Replies View RelatedHas anyone else noticed that after updating to Froyo, that text wrapping/redrawing is not working properly while web-browsing?For example, if you go to a text heavy website, like Reddit, and I zoom in (either by double-tap or pinch), the text will redraw, but it will be slightly larger than the screen's width. To read the text, I am required to scroll a bit to the right, then back to the left, and so on.I never had this problem prior to the Froyo update. Can anyone else confirm that they are having this problem? before I get bombed on, I should say that I am very happy with Froyo in other regards. I have not had any battery drain issues or any lag anywhere. I did not do a factory reset.
View 2 Replies View RelatedI have created a custom component in my program by extending a ViewGroup. This component listens to touch events and are supposed to start animations when the user has move their finger past some certain points.I'm able to start animations while the user is touching the screen. But I'm not able to start animations if the user doesn't move their finger. It's probably that the phone thinks it doesn't have to update the screen if the user isn't moving their finger.I added some logs and according to them the animation starts and ends but it doesn't draw on the screen. I have the same problems when starting an animation with a timer.I use AlphaAnimations and Translate Animations on ImageViews. I have tried to use invalidate() both on the component and the ImageView but it doesn't help.Anyone who has an idea how to solve this?
View 1 Replies View RelatedI was usind ADW for a while and liked it. I like LP better because of the scrollable bar bit when I hit the home key or back up to home, about 50+% of the time it takes ten seconds to redraw. I do ude widgets but it should not be this bad. In settings I tried keeping LP in memory, I set high mem useage and many of the other options and its the same. I even uninstalled wiped cache pulled battery and its the same. Is there a setting config I should be using, or not?
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