比较有意思的ImageView

GuaGuaImageView.java

package com.example.huangxingli.androidshaderabout;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapShader;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Shader;
import android.text.LoginFilter;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.widget.ImageView;

/**
 * Created by huangxingli on 2015/4/7.
 */
public class GuaGuaImageView extends ImageView {
    float dx;
    float dy;
    final float radius=60;
    boolean shouldGua;
    Paint paint;

    public GuaGuaImageView(Context context) {
        super(context);
    }

    public GuaGuaImageView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public GuaGuaImageView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        int action=event.getAction();
        shouldGua=action==MotionEvent.ACTION_DOWN||action==MotionEvent.ACTION_MOVE;
        dx=event.getX();
        dy=event.getY();
        invalidate();
        return true;
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        if (paint==null){
            paint=new Paint();
            Bitmap bitmap= Bitmap.createBitmap(getWidth(),getHeight(), Bitmap.Config.ARGB_8888);
            Log.v("TAG","====GETWIDTH IS "+getWidth());
            Canvas originCanvas=new Canvas(bitmap);
            super.onDraw(originCanvas);
            BitmapShader bitmapShader=new BitmapShader(bitmap, Shader.TileMode.CLAMP, Shader.TileMode.CLAMP);
            paint.setShader(bitmapShader);
        }
        canvas.drawColor(Color.GRAY);
        if (shouldGua) {
            //dx dy circle的圆心的x y轴坐标
            //radius半径长度
            canvas.drawCircle(dx, dy, radius, paint);
        }


    }
}