Best practices for Android graffiti

Best practices for Android graffiti

In Android, there are two ways to implement gesture plotting. One is to draw directly on the View, but to use SurfaceView. There are some differences between the two. View: display View, built-in canvas, provides graphics rendering functions, touch screen events, button event functions, etc. You must update the screen in the main UI thread, the speed is slow. SurfaceView: Expanded view Class Based on view, which is more suitable for the development of 2D games. It is a subclass of view and uses the double easing mechanism, refreshing the interface is faster than refreshing the view because the screen is updated in the new thread. Therefore, the latter should be preferred for graffiti.

Before starting the code, let's simply look at the functions to be implemented.

1. You can customize the paint brush color.

2. You can customize the paint brush width.

3. Various common shapes can be drawn.

4. To allow the canvas to be rolled back, return to the previous step.

5. Support the eraser Function

6. Save the finished painting.

Next we will gradually implement these five features.

1. For the color and width of a custom Paint brush, the simplest method is to call the setColor (int color) and setStrokeWidth (float width) Methods of painting. It is important to note that SurfaceView is used to draw a Canvas instance through SurfaceHolder. In this case, you can draw a Canvas instance and call unlockCanvasAndPost (canvas) to submit the changes after the painting ends.

2. Supports free curves, straight lines, rectangles, circles, solid rectangles, and solid circles for convenient extension. Here, we first abstract a base class Action. Every draw is an action instance, and our canvas is a list of actions, so that the rollback function can be well supported.

3. roll back the canvas. If the action list on the canvas is not 0, it indicates that the canvas currently supports rollback. You only need to remove the last action from the list and redraw it. <喎?http: www.bkjia.com kf ware vc " target="_blank" class="keylink"> VcD4KPHA + CjxpbWcgc3JjPQ = "http://www.2cto.com/uploadfile/Collfiles/20140903/2014090308253764.jpg" alt = "\">

4. eraser. Here I took a coincidence that the canvas background is white, so the implementation of the eraser is also an action, the shape is a free curve, the color is also white, in this way, a erased effect is created, but it is actually covered by a white curve. According to the implementation of the third point, the eraser also supports rollback.

5. Save the canvas. The canvas is full of your various images. The last step is to save them, but the screenshot of the View and SurfaceView is different. The View is static and passive, and the SurfaceView is active and dynamic, if you use the View method, you can only obtain one black screen. In this case, we can re-plot the saved action list. The Code is as follows:

Address: https://github.com/JackCho/AndroidDoodle

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