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Editor to share with you how to use a resource picture in StateBackgroundUtil to set up a background with press effect for View. I believe most people don't know much about it, so share this article for your reference. I hope you will gain a lot after reading this article. Let's learn about it together.

How to use a resource picture to set the background drawable with a press effect for View.

Origin

Some time ago, in the process of developing a new version of the project, the designer issued a set of press effect specifications for the project. The specification goes something like this.

For a general button, there are only two different implementations of the effect of pressing the button.

1. Darken the front background image after pressing, specifically by adding a 20% black mask on top of the normal drawable.

2. Reduce the transparency of the front background resources after pressing. Specifically, the drawable transparency of the normal state is changed to 70% when pressed.

Obviously, this set of specifications will bring the following benefits.

When drawing, the designer only needs to produce a picture, and then only needs to tell the developer to press the effect strategy, which can reduce the designer's burden of drawing.

On the client side, there is no need to import two resource images to achieve a press effect, which reduces the package size and saves the client developer the trouble of writing selector files.

Realization scheme

In fact, in the previous development process, I also had this thought about how to set the background of View according to a picture and make it have a press effect. At first, I naturally thought of dealing with the touch event of View, and then dynamically pressed the background resource according to the normal background setting when pressed.

But later, I felt that it was still troublesome, and sometimes some View itself needed to deal with touch events, which would cause conflicts, so it was over at that time.

This time, after some search, thinking, and finally using StateListDrawable to achieve the goal.

StateListDrawable has a method addState for setting drawable in different states, including press, focus, unavailable, and so on.

Therefore, to meet the demand, you only need to calculate the pressed state drawable based on the drawable in the normal state, and then set the pressed state to * implement a set of resources to achieve the pressed state of View.

Concrete realization

The solution has been made clear, the implementation is actually very simple, the code is as follows.

/ / Press status stateListDrawable.addState (new int [] {android.R.attr.state_pressed}, pressed); / / normal status stateListDrawable.addState (new int [] {}, normal); return stateListDrawable;}

Process the pressed drawable according to different pressing modes

Private static void setPressedStateDrawable (@ StatePressedMode.Mode int mode, @ FloatRange (from = 0.0f, to = 1.0f) float alpha, @ NonNull Drawable pressed) {switch (mode) {case StatePressedMode.ALPHA: pressed.setAlpha (convertAlphaToInt (alpha)); break; case StatePressedMode.DARK: pressed.setColorFilter (alphaColor (Color.BLACK, convertAlphaToInt (alpha)), PorterDuff.Mode.SRC_ATOP); break Default: pressed.setAlpha (convertAlphaToInt (alpha));}}

At present, the implementation of the scheme has been placed in GitHub, StateBackgroundUtil, welcome to watch and support.

Some details.

When setting the drawable of the pressed state

Drawable normal = context.getResources () .getDrawable (res); Drawable pressed = context.getResources () .getDrawable (res)

The resource res resource used by normal and pressed here is the same id. However, during the loading process of drawable, as long as the same res resource is loaded once in memory, the corresponding state of the drawable will remain the same, so here you need to change the setting of pressed.

Pressed.mutate ()

Official note on the mutate method

This is especially useful when you need to modify properties of drawables loaded from resources. By default, all drawables instances loaded from the same resource share a common state

Deficiency

Color background is not supported (of course you can save the country through the shape curve)

The above is all the content of the article "how to use a resource picture in StateBackgroundUtil to set the background with a press effect for View". Thank you for reading! I believe we all have a certain understanding, hope to share the content to help you, if you want to learn more knowledge, welcome to follow the industry information channel!

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