什么是Drawable ?
Android 把所有显示出来的图形都抽象为drawable ，意思就是可绘制的，包括，图片、色块、背景等。
简单的drawable都是静态的图形，当然也有其他的，比如StateListDrawable，可以根据不同的触摸来变换不同的图形。也是通常我们在drawable文件中创建的selector.xml
我们通过简单三个例子来了解一下自定义drawable
效果图
图片圆形的实现
/*** 圆形图片实现*/public class CircleDrawable extends BitmapDrawable {private final Paint mPaint;public CircleDrawable(Resources resources, Bitmap bitmap){super(resources,bitmap);BitmapShader shader=new BitmapShader(bitmap, Shader.TileMode.CLAMP, Shader.TileMode.CLAMP);mPaint = new Paint();mPaint.setAntiAlias(true);mPaint.setShader(shader);mPaint.setColor(Color.RED);}@Overridepublic void draw(Canvas canvas) {int width = getBitmap().getWidth();int height = getBitmap().getHeight();int radius = Math.min(width/2, height/2);int x = (width>radius+radius)?width/2:radius;int y = (height>radius+radius)?height/2:radius;canvas.drawCircle(x,y,radius,mPaint);}/*** 这两个方法可以获取到drawable绘制的区域，不过ImageView的源码中调用的是下面的* @param bounds*/@Overridepublic void setBounds(Rect bounds) {super.setBounds(bounds);}/*** 这两个方法可以获取到drawable绘制的区域 Imagview中会调用该方法，设置宽高*/@Overridepublic void setBounds(int left, int top, int right, int bottom) {super.setBounds(left, top, right, bottom);}}
图片圆角的实现
/*** 圆角图片实现*/public class RoundDrawable extends BitmapDrawable {private final Paint paint;private float radisu;private RectF rectF;public RoundDrawable(Resources resources, Bitmap bitmap){super(resources,bitmap);BitmapShader shader=new BitmapShader(bitmap, Shader.TileMode.CLAMP, Shader.TileMode.CLAMP);paint = new Paint();paint.setAntiAlias(true);paint.setShader(shader);}@Overridepublic void draw(Canvas canvas) {canvas.drawRoundRect(rectF,radisu,radisu,paint);}public void setRadius(float radisu){this.radisu = radisu;}@Overridepublic void setBounds(int left, int top, int right, int bottom) {rectF = new RectF(left,top,right,bottom);}}
椭圆图片的实现
/*** 椭圆图片实现*/public class OvalDrawable extends BitmapDrawable {private final Paint mPaint;private RectF rectF;public OvalDrawable(Resources res, Bitmap bitmap){super(res,bitmap);BitmapShader shader=new BitmapShader(bitmap, Shader.TileMode.CLAMP, Shader.TileMode.CLAMP);mPaint = new Paint();mPaint.setAntiAlias(true);mPaint.setDither(true);mPaint.setShader(shader);}@Overridepublic void draw(Canvas canvas) {canvas.drawOval(rectF,mPaint);}@Overridepublic void setBounds(int left, int top, int right, int bottom) {super.setBounds(left, top, right, bottom);rectF = new RectF(left,top,right,bottom);}}
按钮点击调用
public void onClick(View v) {switch (v.getId()) {case R.id.original: // 原图imageView.setImageResource(R.drawable.demo);break;case R.id.circle: // 圆形Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.demo);CircleDrawable drawable = new CircleDrawable(getResources(), bitmap);imageView.setImageDrawable(drawable);break;case R.id.round: // 圆角Bitmap roundBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.demo);RoundDrawable roundDrawable = new RoundDrawable(getResources(), roundBitmap);roundDrawable.setRadius(30);imageView.setImageDrawable(roundDrawable);break;case R.id.oval: // 椭圆Bitmap ovalBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.demo);OvalDrawable ovalDrawable = new OvalDrawable(getResources(), ovalBitmap);imageView.setImageDrawable(ovalDrawable);break;}}
MainActivity界面xml
<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="/apk/res/android"xmlns:tools="/tools"android:id="@+id/activity_main"android:layout_width="match_parent"android:layout_height="match_parent"android:orientation="vertical"tools:context="com.lg.customdrawable.MainActivity"><ImageView android:id="@+id/image_view"android:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_marginLeft="5dp"android:layout_marginRight="5dp"android:src="@drawable/demo" /><LinearLayout android:layout_width="match_parent"android:layout_height="wrap_content"android:orientation="horizontal"><Button android:id="@+id/original"android:layout_width="0dp"android:layout_height="wrap_content"android:layout_weight="1"android:text="原图" /><Button android:id="@+id/circle"android:layout_width="0dp"android:layout_height="wrap_content"android:layout_weight="1"android:text="圆形" /><Button android:id="@+id/round"android:layout_width="0dp"android:layout_height="wrap_content"android:layout_weight="1"android:text="圆角" /><Button android:id="@+id/oval"android:layout_width="0dp"android:layout_height="wrap_content"android:layout_weight="1"android:text="椭圆" /></LinearLayout></LinearLayout>
总结
简单实现了三种效果，帮助理解自定义Drawable。
Demo下载地址有需要的可以看下
