setShadpwLayer实现阴影效果

package com.loaderman.customviewdemo;

import android.content.Context;
import android.graphics.*;
import android.util.AttributeSet;
import android.view.View;

public class ShadowLayerView extends View {
    private Paint mPaint = new Paint();
    private Bitmap mDogBmp;
    private int mRadius = 1, mDx = 10, mDy = 10;
    private boolean mSetShadow = true;

    public ShadowLayerView(Context context) {
        super(context);
        init();
    }

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

    public ShadowLayerView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        init();
    }

    private void init() {
        setLayerType(LAYER_TYPE_SOFTWARE, null);
        mPaint.setColor(Color.BLACK);
        mPaint.setTextSize(25);
        mDogBmp = BitmapFactory.decodeResource(getResources(), R.drawable.dog);
    }

    public void changeRadius() {
        mRadius++;
        postInvalidate();
    }

    public void changeDx() {
        mDx += 5;
        postInvalidate();
    }

    public void changeDy() {
        mDy += 5;
        postInvalidate();
    }

    public void setShadow(boolean showShadow) {
        mSetShadow = showShadow;
        postInvalidate();
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);

        canvas.drawColor(Color.WHITE);

        if (mSetShadow) {
            mPaint.setShadowLayer(mRadius, mDx, mDy, Color.GRAY);
        } else {
            mPaint.clearShadowLayer();
        }

        canvas.drawText("启舰", 100, 100, mPaint);

        canvas.drawCircle(200, 200, 50, mPaint);

        canvas.drawBitmap(mDogBmp, null, new Rect(200, 300, 200 + mDogBmp.getWidth(), 300 + mDogBmp.getHeight()), mPaint);
    }
}

package com.loaderman.customviewdemo;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;

public class MainActivity extends Activity  implements View.OnClickListener{

    private ShadowLayerView mShadowLayerView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mShadowLayerView = (ShadowLayerView)findViewById(R.id.shadowlayerview);
        findViewById(R.id.radius_btn).setOnClickListener(this);
        findViewById(R.id.dx_btn).setOnClickListener(this);
        findViewById(R.id.dy_btn).setOnClickListener(this);
        findViewById(R.id.clear_btn).setOnClickListener(this);
        findViewById(R.id.show_btn).setOnClickListener(this);
    }
    public void onClick(View v) {
        switch (v.getId()){
            case R.id.radius_btn:
                mShadowLayerView.changeRadius();
                break;
            case R.id.dx_btn:
                mShadowLayerView.changeDx();;
                break;
            case R.id.dy_btn:
                mShadowLayerView.changeDy();
                break;
            case R.id.clear_btn:
                mShadowLayerView.setShadow(false);
                break;
            case R.id.show_btn:
                mShadowLayerView.setShadow(true);
                break;
        }
    }
}

效果:

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setShadowLayer(float radius, float dx, float dy, int shadowColor)

radius 模糊半径
dx和dy偏移距离
shadowColor绘制阴影的画笔颜色,对图片无效