android实现圆角矩形背景的方法

import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.ColorFilter;
import android.graphics.Paint;
import android.graphics.Rect;
import android.graphics.drawable.Drawable;
import android.graphics.drawable.shapes.RoundRectShape;
import android.view.MotionEvent;
public class RoundRectDradable extends Drawable{
  private static final float DEFAULT_RADIUS = 6.f;
  private Paint mPaint = new Paint();
  private RoundRectShape mShape;
  private float[] mOuter;
  private int mColor;
  private int mPressColor;
  private float mTopLeftRadius = DEFAULT_RADIUS;
  private float mTopRightRadius = DEFAULT_RADIUS;
  private float mBottomLeftRadius = DEFAULT_RADIUS;
  private float mBottomRightRadius = DEFAULT_RADIUS;
  public RoundRectDradable() {
    mColor = Color.WHITE;
    mPressColor = Color.WHITE;
    mPaint.setColor(mColor);
    mPaint.setAntiAlias(true);
  }
  public float getTopLeftRadius() {
    return mTopLeftRadius;
  }
  public void setTopLeftRadius(float topLeftRadius) {
    this.mTopLeftRadius = topLeftRadius;
  }
  public float getTopRightRadius() {
    return mTopRightRadius;
  }
  public void setTopRightRadius(float topRightRadius) {
    this.mTopRightRadius = topRightRadius;
  }
  public float getBottomLeftRadius() {
    return mBottomLeftRadius;
  }
  public void setBottomLeftRadius(float bottomLeftRadius) {
    this.mBottomLeftRadius = bottomLeftRadius;
  }
  public float getBottomRightRadius() {
    return mBottomRightRadius;
  }
  public void setBottomRightRadius(float bottomRightRadius) {
    this.mBottomRightRadius = bottomRightRadius;
  }
  public int getPressColor() {
    return mPressColor;
  }
  public void setPressColor(int pressColor) {
    this.mPressColor = pressColor;
  }
  @Override
  protected void onBoundsChange(Rect bounds) {
    super.onBoundsChange(bounds);
    refreshShape();
    mShape.resize(bounds.right - bounds.left, bounds.bottom - bounds.top);
  }
  private void refreshShape(){
    mOuter = new float[]{mTopLeftRadius, mTopLeftRadius
        , mTopRightRadius, mTopRightRadius
        , mBottomLeftRadius, mBottomLeftRadius
        , mBottomRightRadius, mBottomLeftRadius};
    mShape = new RoundRectShape(mOuter, null, null);
  }
  public void setColor(int color){
    mColor = color;
    mPaint.setColor(color);
  }
  @Override
  public void draw(Canvas canvas) {
    mShape.draw(canvas, mPaint);
  }
  @Override
  public void setAlpha(int alpha) {
    mPaint.setAlpha(alpha);
  }
  @Override
  public void setColorFilter(ColorFilter cf) {
    mPaint.setColorFilter(cf);
  }
  @Override
  public int getOpacity() {
    return mPaint.getAlpha();
  }
}

import android.graphics.Rect;
import android.graphics.drawable.StateListDrawable;
public class StateRoundRectDrawable extends StateListDrawable{
  private static final float DEFAULT_RADIUS = 6.f;
  private float mTopLeftRadius = DEFAULT_RADIUS;
  private float mTopRightRadius = DEFAULT_RADIUS;
  private float mBottomLeftRadius = DEFAULT_RADIUS;
  private float mBottomRightRadius = DEFAULT_RADIUS;
  private int mNormalColor;
  private int mPressedColor;
  private RoundRectDradable mNormalDradable;
  private RoundRectDradable mPressedDradable;
  public StateRoundRectDrawable(int normalCorlor, int pressColor) {
    this.mNormalColor = normalCorlor;
    this.mPressedColor = pressColor;
  }
  @Override
  protected void onBoundsChange(Rect bounds) {
    if(mNormalDradable == null){
      mNormalDradable = new RoundRectDradable();
      mNormalDradable.setTopLeftRadius(mTopLeftRadius);
      mNormalDradable.setTopRightRadius(mTopRightRadius);
      mNormalDradable.setBottomLeftRadius(mBottomLeftRadius);
      mNormalDradable.setBottomRightRadius(mBottomRightRadius);
      mNormalDradable.setColor(mNormalColor);
      mNormalDradable.onBoundsChange(bounds);
    }
    if(mPressedDradable == null){
      mPressedDradable = new RoundRectDradable();
      mPressedDradable.setTopLeftRadius(mTopLeftRadius);
      mPressedDradable.setTopRightRadius(mTopRightRadius);
      mPressedDradable.setBottomLeftRadius(mBottomLeftRadius);
      mPressedDradable.setBottomRightRadius(mBottomRightRadius);
      mPressedDradable.setColor(mPressedColor);
      mPressedDradable.onBoundsChange(bounds);
    }
    this.addState(new int[]{-android.R.attr.state_pressed}, mNormalDradable);
    this.addState(new int[]{android.R.attr.state_pressed}, mPressedDradable);
  }
  public float getTopLeftRadius() {
    return mTopLeftRadius;
  }
  public void setTopLeftRadius(float topLeftRadius) {
    this.mTopLeftRadius = topLeftRadius;
  }
  public float getTopRightRadius() {
    return mTopRightRadius;
  }
  public void setTopRightRadius(float topRightRadius) {
    this.mTopRightRadius = topRightRadius;
  }
  public float getBottomLeftRadius() {
    return mBottomLeftRadius;
  }
  public void setBottomLeftRadius(float bottomLeftRadius) {
    this.mBottomLeftRadius = bottomLeftRadius;
  }
  public float getBottomRightRadius() {
    return mBottomRightRadius;
  }
  public void setBottomRightRadius(float bottomRightRadius) {
    this.mBottomRightRadius = bottomRightRadius;
  }
  public int getNormalColor() {
    return mNormalColor;
  }
  public void setNormalColor(int normalColor) {
    this.mNormalColor = normalColor;
  }
  public int getPressedColor() {
    return mPressedColor;
  }
  public void setPressedColor(int pressedColor) {
    this.mPressedColor = pressedColor;
  }
}