Drawable 综述

Drwable看似简单，在平时的应用中也不少，但是一般只是简单的应用,涉及到的覆盖面十分光，今天我们就来扒一扒drawble的的详情

Drawble是对可绘制物件的一般抽象，相对于View缺少一些和事件交互的方法

大致分类:Bitmap,AnimationDrawable,Levels,Nine Patch,Scale,shape,Layers,states

Drawble常用API:

   setBounds();控制大小

   draw(Canvas canvas) 绘制

自定义Drawble 如圆角图片,圆形图片

先来介绍一个特殊的类Shader,这个类主要是用于渲染图像以及一些几何图形

Shader有几个直接子类：

BitmapShader:主要用于渲染图像

LinearGradient:用来进行线性渲染

RedialGradient:用来进行环形渲染

SweepGradient:扫描渐变 围绕一个中心点，360等安全扫描

ComposeShader:组合渲染，可以和其他几个子类组合起来使用

1:BitampShader

   渲染器着色一个位图作为一个纹理，位图可以重复或设置模式

    /**     * Call this to create a new shader that will draw with a bitmap.     *     * @param bitmap            The bitmap to use inside the shader     * @param tileX             The tiling mode for x to draw the bitmap in.     * @param tileY             The tiling mode for y to draw the bitmap in.     */    public BitmapShader(@NonNull Bitmap bitmap, TileMode tileX, TileMode tileY) {        mBitmap = bitmap;        mTileX = tileX;        mTileY = tileY;        init(nativeCreate(bitmap, tileX.nativeInt, tileY.nativeInt));    }

调用这个方法来产生一个画有一个位图的渲染器(Shader)

Bitmap  在渲染器内使用的位图

tileX 在为位图上X方向瓷砖模式

tileY 在位图上Y方向瓷砖模式

public enum TileMode {        /**         * replicate the edge color if the shader draws outside of its         * original bounds         */        CLAMP   (0),        /**         * repeat the shader's image horizontally and vertically         */        REPEAT  (1),        /**         * repeat the shader's image horizontally and vertically, alternating         * mirror images so that adjacent images always seam         */        MIRROR  (2);            TileMode(int nativeInt) {            this.nativeInt = nativeInt;        }        final int nativeInt;    }

TitleModo 一共有三种

CLAMP:如果渲染器超出原始边界范围，会复制范围内边缘染色

REPEADT:横向和纵向的重复渲染器图片，平铺

MIRROR:横向和纵向的重复渲染器图片，这个和REPEAR重复方式不一样，他是以镜像方式平铺

2:LinearGradient

/** Create a shader that draws a linear gradient along a line.        @param x0           The x-coordinate for the start of the gradient line        @param y0           The y-coordinate for the start of the gradient line        @param x1           The x-coordinate for the end of the gradient line        @param y1           The y-coordinate for the end of the gradient line        @param  colors      The colors to be distributed along the gradient line        @param  positions   May be null. The relative positions [0..1] of                            each corresponding color in the colors array. If this is null,                            the the colors are distributed evenly along the gradient line.        @param  tile        The Shader tiling mode    */    public LinearGradient(float x0, float y0, float x1, float y1, int colors[], float positions[],            TileMode tile) {        if (colors.length < 2) {            throw new IllegalArgumentException("needs >= 2 number of colors");        }        if (positions != null && colors.length != positions.length) {            throw new IllegalArgumentException("color and position arrays must be of equal length");        }        mType = TYPE_COLORS_AND_POSITIONS;        mX0 = x0;        mY0 = y0;        mX1 = x1;        mY1 = y1;        mColors = colors;        mPositions = positions;        mTileMode = tile;        init(nativeCreate1(x0, y0, x1, y1, colors, positions, tile.nativeInt));    }

x0: 渐变起初点坐标x位置

y0: 渐变起初点坐标y位置

x1:渐变终点坐标x位置

y1:渐变终点坐标y位置

colors 渐变的颜色

positions 渐变颜色对应的位置

tile 平铺方式

LinearGradient是线性渐变的，用法如下:

Gradient是居于Shader类，所以我们要通过Paint的setShader方法来设置这个渐变,

代码如下:

Paint paint=new Paint();

//也可采用颜色位置数组方式LinearGradient lg=new LinearGradient(0,0,100,100, Color.RED,Color.BLUE, Shader.TileMode.MIRROR);paint.setShader(lg);

canvas.drawCircle(0,0,200,paint);

下面来看一下例子:

package com.example.drawablestudy.shader;import android.content.Context;import android.graphics.Bitmap;import android.graphics.BitmapShader;import android.graphics.Canvas;import android.graphics.Shader;import android.graphics.drawable.BitmapDrawable;import android.graphics.drawable.Drawable;import android.graphics.drawable.ShapeDrawable;import android.graphics.drawable.shapes.OvalShape;import android.util.AttributeSet;import android.view.View;import com.example.drawablestudy.R;/** * @author xuanyouwu * @email [e-mail] * @time 2016-01-16 12:51 */public class MyBitmapShader extends View {    public MyBitmapShader(Context context) {        super(context);        initBitmap();    }    public MyBitmapShader(Context context, AttributeSet attrs) {        super(context, attrs);        initBitmap();    }    public MyBitmapShader(Context context, AttributeSet attrs, int defStyleAttr) {        super(context, attrs, defStyleAttr);        initBitmap();    }    private Drawable d;    private Bitmap b;    private BitmapShader shader;    private void initBitmap() {        d = getResources().getDrawable(R.drawable.car2);        b = ((BitmapDrawable) d).getBitmap();        shader = new BitmapShader(b, Shader.TileMode.REPEAT, Shader.TileMode.MIRROR);    }    @Override    protected void onDraw(Canvas canvas) {        super.onDraw(canvas);        //将图片裁剪为椭圆        //构建ShapeDrawable对象并定义形状为椭圆形        ShapeDrawable sha = new ShapeDrawable(new OvalShape());        sha.getPaint().setShader(shader);        sha.setBounds(20, 20, canvas.getWidth(), canvas.getHeight());        sha.draw(canvas);    }}

Shape类型详解

  Shape类型用来绘制集合图形，易用而轻量化

  Shape通常用xml文件方式使用，存放在drawable目录下

 shape主要API：

 /**     * Draw this shape into the provided Canvas, with the provided Paint.     * Before calling this, you must call {@link #resize(float,float)}.     *      * @param canvas the Canvas within which this shape should be drawn     * @param paint  the Paint object that defines this shape's characteristics     */    public abstract void draw(Canvas canvas, Paint paint);    /**     * Resizes the dimensions of this shape.     * Must be called before {@link #draw(Canvas,Paint)}.     *      * @param width the width of the shape (in pixels)     * @param height the height of the shape (in pixels)     */    public final void resize(float width, float height) {        if (width < 0) {            width = 0;        }        if (height < 0) {            height =0;        }        if (mWidth != width || mHeight != height) {            mWidth = width;            mHeight = height;            onResize(width, height);        }    }    

Shape的类型:

  RectShape 矩形,直角矩形,圆角矩形等

 OvalShape  椭圆形,圆形

 PathShape 线性,环形等

 Ring,Line 环形,环形进度条,线性，实线，虚线

 ArcShape 弧形