本文主要是介绍自定义View实现阴影，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
其实实现阴影Android系统自带android:elevation实现阴影功能，但是在低版本系统可能就无效了，当然还可以使用shape.xml实现，CardView也可以实行阴影功能，但是尴尬的是不知道怎么切换阴影的颜色。
上图中图一是使用setShadowLayer实现的阴影效果
上图中图二是使用 setMaskFilter(new BlurMaskFilter(50,BlurMaskFilter.Blur.SOLID));
- 实现图一完整代码
定义几个属性
<declare-styleable name="ShadowLayerView"><attr name="elevate" format="integer"/><attr name="elevationColor" format="color"/><attr name="shape" format="enum"><enum name="shapeRect" value="1"/><enum name="circle" value="2"/><enum name="round" value="3"/></attr><attr name="roundRx" format="integer"/><attr name="roundRy" format="integer"/></declare-styleable>
import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Rect;
import android.os.Build;
import android.support.annotation.Nullable;
import android.support.annotation.RequiresApi;
import android.util.AttributeSet;
import android.view.View;import com.jewelermobile.gangfu.zdydemo1.R;public class ShadowLayerView extends View {/**阴影*/private int elevation;/**阴影的颜色*/private int elevationColor;/**view的形状*/private int shape = 1;private static final int shapeRect = 1 ;private static final int circle = 2 ;private static final int round = 3 ;/**圆角 x轴半径*/private int roundRx ;/**圆角 y轴半径*/private int roundRy ;public ShadowLayerView(Context context) {this(context,null);}public ShadowLayerView(Context context, @Nullable AttributeSet attrs) {this(context, attrs,0);}public ShadowLayerView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {super(context, attrs, defStyleAttr);TypedArray array = context.obtainStyledAttributes(attrs,R.styleable.ShadowLayerView,0,defStyleAttr);int count = array.getIndexCount();for (int i = 0 ; i<count ; i++){int attr = array.getIndex(i);switch (attr){case R.styleable.ShadowLayerView_elevate:elevation = array.getInt(attr,20);break;case R.styleable.ShadowLayerView_elevationColor:elevationColor = array.getColor(attr,Color.RED);break;case R.styleable.ShadowLayerView_shape:shape = array.getInt(attr,shapeRect);break;case R.styleable.ShadowLayerView_roundRx:roundRx = array.getInt(attr,0);break;case R.styleable.ShadowLayerView_roundRy:roundRy = array.getInt(attr,0);break;}}array.recycle();}@RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)@Overrideprotected void onDraw(Canvas canvas) {super.onDraw(canvas);Paint paint=new Paint(Paint.ANTI_ALIAS_FLAG);paint.setStrokeWidth(10);paint.setColor(Color.BLUE);paint.setStyle(Paint.Style.FILL);paint.setShadowLayer(elevation,0,0,elevationColor);Rect rect=new Rect(getPaddingLeft(),getPaddingTop(),getWidth()-getPaddingRight(),getBottom()-getPaddingBottom());switch (shape){case shapeRect:canvas.drawRect(rect,paint);break;case circle:int r= Math.min(getWidth(),getHeight())/2;canvas.drawCircle(r+getPaddingLeft(),r+getPaddingTop(),r-getPaddingLeft()-getPaddingRight(),paint);break;case round:canvas.drawRoundRect(rect.left,rect.top,rect.right,rect.bottom,roundRx,roundRy,paint);break;}}/*** @param val* @return*/public int dpToPx(int val){float density = getResources().getDisplayMetrics().density;return (int) (density * val + 0.5f);}}
图二完整代码
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.BitmapShader;
import android.graphics.BlurMaskFilter;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Shader;
import android.support.annotation.Nullable;
import android.util.AttributeSet;
import android.view.View;import com.jewelermobile.gangfu.zdydemo1.R;public class BitmapShaderView extends View {int radius = 300 ;public BitmapShaderView(Context context) {this(context,null);}public BitmapShaderView(Context context, @Nullable AttributeSet attrs) {this(context, attrs,0);}public BitmapShaderView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {super(context, attrs, defStyleAttr);}@Overrideprotected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {if (radius>0){setMeasuredDimension(radius*2+getPaddingLeft()+getPaddingRight(),radius*2+getPaddingTop()+getPaddingBottom());}else {super.onMeasure(widthMeasureSpec, heightMeasureSpec);}}@Overrideprotected void onDraw(Canvas canvas) {super.onDraw(canvas);Paint paint=new Paint(Paint.ANTI_ALIAS_FLAG);Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.mipmap.a0);/*** replicate the edge color if the shader draws outside of its* original bounds* CLAMP (0), 拉伸* repeat the shader's image horizontally and vertically* REPEAT (1),* repeat the shader's image horizontally and vertically, alternating* mirror images so that adjacent images always seam* IRROR (2);*/BitmapShader bitmapShader=new BitmapShader(bitmap, Shader.TileMode.CLAMP,Shader.TileMode.CLAMP);paint.setShader(bitmapShader);paint.setColor(Color.RED);/*** Blur inside and outside the original border.NORMAL(0),* Draw solid inside the border, blur outside.SOLID(1),* Draw nothing inside the border, blur outside.OUTER(2),* Blur inside the border, draw nothing outside.INNER(3);*/paint.setMaskFilter(new BlurMaskFilter(50,BlurMaskFilter.Blur.SOLID));canvas.drawCircle(radius+getPaddingLeft(),radius+getPaddingTop(),radius,paint);}
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