View去锯齿，在有些机器需要在图层的软件层才能实现

来源：互联网发布：熊猫加速器mac版编辑：程序博客网时间：2024/05/18 00:05

众所周知，android绘图抗锯齿常规方法有两种：一种在Paint设置，一种在Canvas设置：

package com.example.root.antialias;import android.content.Context;import android.graphics.Bitmap;import android.graphics.BitmapFactory;import android.graphics.Canvas;import android.graphics.Matrix;import android.graphics.Paint;import android.graphics.PaintFlagsDrawFilter;import android.util.AttributeSet;import android.util.Log;import android.view.View;/** * Created by root on 7/31/16. */public class AntiAliasView extends View {    private PaintFlagsDrawFilter paintFlagsDrawFilter;    private Matrix mMatrix = new Matrix();    private Paint mPaint = new Paint();    private Bitmap bitmap;    public AntiAliasView(Context context, AttributeSet attributeSet){        super(context,attributeSet);        if(this.isHardwareAccelerated()){            Log.d("vfp8341","Opened");            setLayerType(View.LAYER_TYPE_SOFTWARE, null);            Log.d("vfp8341","If hardWareAccelerated:" + this.isHardwareAccelerated());        }else {            Log.d("vfp8341","Closed");            Log.d("vfp8341","LayerType  before:" + getLayerType());            setLayerType(View.LAYER_TYPE_SOFTWARE, null);            Log.d("vfp8341","LayerType   after:" + getLayerType());            Log.d("vfp8341","If hardWareAccelerated:" + this.isHardwareAccelerated());        }        paintFlagsDrawFilter = new PaintFlagsDrawFilter(0, Paint.ANTI_ALIAS_FLAG|Paint.FILTER_BITMAP_FLAG);        mPaint.setAntiAlias(true);        mPaint.setFilterBitmap(true);        mMatrix.setRotate(-30);        mMatrix.postScale(1.0f, 1.0f);        bitmap = BitmapFactory.decodeResource(getResources(),R.drawable.math);    }    @Override    public void onDraw(Canvas canvas){        super.onDraw(canvas);                canvas.translate(0,100);                   //for the contrast        canvas.drawBitmap(bitmap,mMatrix,null);                canvas.translate(0,260);                   //Paint        canvas.drawBitmap(bitmap,mMatrix,mPaint);                canvas.translate(0, 260);                  //PaintFlagsDrawFilter        canvas.setDrawFilter(paintFlagsDrawFilter);        canvas.drawBitmap(bitmap, mMatrix, null);    }}

在HuaweiG520上运行，如果把构造函数里的if-else去掉，则两种去锯齿方法都无效；如果加上if-else，其实就是一句setLayerType有效，则两种去锯齿方法都生效（G520不支持Studio截图，只好拍照了）。如下是三张图从上到下叠加了的，效果不是太明显，仔细看的话，边沿确实不一样。G520分辨率低，还可勉强看的出来，在N6则完全无效果，锯齿被分辨率消化了：

Log如下：

    08-20 10:04:57.102 2292-2292/com.example.root.antialias D/vfp8341: Closed
    08-20 10:04:57.102 2292-2292/com.example.root.antialias D/vfp8341: LayerType before:0
    08-20 10:04:57.102 2292-2292/com.example.root.antialias D/vfp8341: LayerType   after:1
    08-20 10:04:57.102 2292-2292/com.example.root.antialias D/vfp8341: If hardWareAccelerated:false

View中定义：

    public static final int LAYER_TYPE_HARDWARE = 2;
    public static final int LAYER_TYPE_NONE = 0;
    public static final int LAYER_TYPE_SOFTWARE = 1;

说明在该机器必须在软件层才能开启抗锯齿。之前看过文章说硬件加速会对抗锯齿有影响，但是这种情况下硬件加速一直是关闭的。

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