Android UI development topic (3) Various Drawable

Android UI development topic (3) Various Drawable

This section describes the various Drawable types on the Android platform. graphics. under the drawable package, we can see that there are more than a dozen Drawable classes. What are the relationships and differences between them?

I. AnimationDrawable

As the name suggests, this class mainly represents the animation graphics class, which can achieve frame-by-frame playback. The following code example is as follows:

1. Define a cwj_animation.xml file to be placed in the res/drawable directory. The defined attribute duration is latency, in milliseconds, and the oneshot attribute indicates whether to play only once. The content is:

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2. Calling in java is also very simple.

ImageView img = (ImageView) findViewById (R. id. cwj_image); // first declare an ImageView object in the xml layout File

Img. setBackgroundResource (R. drawable. cwj_animation); // xml file defined by the animation

AnimationDrawable frameAnimation = (AnimationDrawable) img. getBackground (); // constructs the AnimationDrawable object

FrameAnimation. start () // start playing the animation

3. The AnimationDrawable class also provides some common methods as follows:

Void stop () stop

Void addFrame (Drawable frame, int duration) adds a frame, similar to the layout in xml

Drawable getFrame (int index) returns the Drawable image of a frame.

Int getNumberOfFrames () returns the total number of animation frames.

Boolean isOneShot () Whether to play only once

Boolean isRunning () is playing?

Ii. BitmapDrawable

In the Android platform, BitmapDrawable class represents the scaled and deformed Bitmap objects, and its construction method is also very simple, because this class inherits from android. graphics. drawable. drawable provides more bitmap operations than Drawable. The main construction method is as follows:

BitmapDrawable () // construct an empty object directly. This method is not recommended and the SDK is marked as deprecated. It may not be available in the future.

BitmapDrawable (Resources res) // construct from the Resource

BitmapDrawable (Bitmap bitmap) // construct a Bitmap object directly, but it is not recommended.

BitmapDrawable (Resources res, Bitmap bitmap) // create an initial resolution from bitmap from res

BitmapDrawable (String filepath) // It is constructed from a specific file path and is not recommended, but a better one.

BitmapDrawable (Resources res, String filepath) // same as above

BitmapDrawable (InputStream is) // constructed from the input stream. The following method is also recommended.

BitmapDrawable (Resources res, InputStream is) // same as above

Compared with the Drawable class, BitmapDrawable mainly adds the following methods, which are more practical:

Final Bitmap getBitmap () gets a Bitmap object

Int getOpacity () // gets the transparency

Void setAntiAlias (boolean aa) // specifies whether the image is anti-aliasing.

Void setTargetDensity (Canvas canvas) // sets the target Canvas density.

Void setTargetDensity (DisplayMetrics metrics)

3. ClipDrawable

ColorDrawable

Drawable

GradientDrawable

InsetDrawable

LayerDrawable

LevelListDrawable

NinePatchDrawable

PaintDrawable

PictureDrawable

RotateDrawable

ScaleDrawable

ShapeDrawable

StateListDrawable

TransitionDrawable

The above types are rarely used in common development, mainly for the construction and use of base classes, and Multiple widgets in Android are used, interested users can view related content in open-source GIT.