Android开发基于Drawable实现圆角矩形的方法

本文实例讲述了Android开发基于Drawable实现圆角矩形的方法。分享给大家供大家参考，具体如下：

第一步：写个类继承drawable,重写里面的方法，实现的核心代码在draw里

关键技术：BitmapShader

public BitmapShader(Bitmap bitmap,Shader.TileMode tileX,Shader.TileMode tileY)

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 The tiling mode for x to draw the bitmap in. 在位图上X方向渲染器平铺模式
tileY The tiling mode for y to draw the bitmap in. 在位图上Y方向渲染器平铺模式

TileMode：
CLAMP ：如果渲染器超出原始边界范围，会复制范围内边缘染色。
REPEAT ：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REPEAT重复方式不一样，他是以镜像方式平铺。

public class RoundImageDrawable extends Drawable {
 private Paint mPaint;
 private Bitmap mBitmap;
 private RectF mRectF;
 private int mRound;
 public RoundImageDrawable(Bitmap bitmap) {
  this.mBitmap = bitmap;
  mPaint = new Paint();
  mPaint.setAntiAlias(true);
  BitmapShader shader = new BitmapShader(mBitmap, TileMode.CLAMP, TileMode.CLAMP);
  mPaint.setShader(shader);
 }
 
 @Override
 public void setBounds(int left, int top, int right, int bottom) {
  mRectF = new RectF(left, top, right, bottom);
  super.setBounds(left, top, right, bottom);
 }
 
 @Override
 public void draw(Canvas canvas) {
  canvas.drawRoundRect(mRectF, mRound, mRound, mPaint);
 }
 
 public void setRound(int round) {
  this.mRound = round;
 }
 
 @Override
 public int getIntrinsicHeight() {
  return mBitmap.getHeight();
 }
 @Override
 public int getIntrinsicWidth() {
  return mBitmap.getWidth();
 }
 
 @Override
 public void setAlpha(int alpha) {
  mPaint.setAlpha(alpha);
 }
 
 @Override
 public void setColorFilter(ColorFilter cf) {
  mPaint.setColorFilter(cf);
 }
 @Override
 public int getOpacity() {
  return PixelFormat.TRANSLUCENT;
 }
}

第二步：实现类

public class RoundActivity extends Activity {
 private ImageView mImageView;
 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_round_drawable);
  setContentView(R.layout.activity_round_drawable);
  mImageView = (ImageView) findViewById(R.id.iv_round);
  Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.aa);
  RoundImageDrawable drawable = new RoundImageDrawable(bitmap);
  drawable.setRound(30);
  mImageView.setImageDrawable(drawable); }
}

activity_round_drawable.xml

绘制圆形图片

核心代码：

mWidth = Math.min(bitmap.getWidth(), bitmap.getHeight());
canvas.drawCircle(mWidth / 2, mWidth / 2, mRadius, mPaint);

public class CircleImageDrawable extends Drawable {
  private Bitmap mBitmap;
  private Paint mPaint;
  private int mWidth;
  private int mRadius;
  public CircleImageDrawable(Bitmap bitmap){
    this.mBitmap = bitmap;
    mPaint.setAntiAlias(true);
    BitmapShader shader = new BitmapShader(mBitmap, TileMode.CLAMP, TileMode.CLAMP);
    mPaint.setShader(shader);
    mWidth = Math.min(bitmap.getWidth(), bitmap.getHeight());
    mRadius = mWidth / 2;
  }
  
  @Override
  public void draw(Canvas canvas) {
    canvas.drawCircle(mWidth / 2, mWidth / 2, mRadius, mPaint);
  }
  
  @Override
  public int getIntrinsicHeight() {
    return mWidth;
  }
  @Override
  public int getIntrinsicWidth() {
    return mWidth;
  }
  @Override
  public void setAlpha(int alpha) {
    mPaint.setAlpha(alpha);
  }
  @Override
  public void setColorFilter(ColorFilter cf) {
    mPaint.setColorFilter(cf);
  }
  @Override
  public int getOpacity() {
    return PixelFormat.TRANSLUCENT;
  }
}

更多关于Android相关内容感兴趣的读者可查看本站专题：《Android图形与图像处理技巧总结》、《Android开发入门与进阶教程》、《Android调试技巧与常见问题解决方法汇总》、《Android基本组件用法总结》、《Android视图View技巧总结》、《Android布局layout技巧总结》及《Android控件用法总结》

希望本文所述对大家Android程序设计有所帮助。