背景
項目中測試反饋在Android P以下圖片邊黑了。看了一下項目代碼發現是自定義圓角圖片View造成的,review 代碼發現實現原理很簡單。就是如下圖繪製出四個黃色的角,蓋在圖片上就行了。(PS:圖畫的比較粗糙,大家見諒)
先上代碼
package com.wzc.xfermodedemo.view;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.PorterDuff;
import android.graphics.PorterDuffXfermode;
import android.graphics.RectF;
import android.util.AttributeSet;
import androidx.annotation.Nullable;
import androidx.appcompat.widget.AppCompatImageView;
/**
* Author: Wuzuchang
* Date: 2020/4/4 12:24
* Description: Test
*/
public class RoundImageView extends AppCompatImageView {
private Paint mPaint;
private RectF mRoundRectF;
private Path mRoundPath;
private Path mRectanglePath;
private int mViewWidth;
private int mViewHeight;
private float[] mCornerRadius = new float[]{50, 50, 50, 50, 50, 50, 50, 50};
public RoundImageView(Context context) {
super(context);
initView();
}
public RoundImageView(Context context, @Nullable AttributeSet attrs) {
super(context, attrs);
initView();
}
public RoundImageView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
initView();
}
private void initView() {
mRoundRectF = new RectF();
mRoundPath = new Path();
mRectanglePath = new Path();
mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
mPaint.setColor(Color.BLUE);
mPaint.setStyle(Paint.Style.FILL);
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
mViewWidth = w;
mViewHeight = h;
mRoundRectF.set(0, 0, w, h);
mRoundPath.reset();
mRoundPath.addRoundRect(mRoundRectF, mCornerRadius, Path.Direction.CW);
mRectanglePath.reset();
mRectanglePath.addRect(mRoundRectF, Path.Direction.CW);
mRectanglePath.op(mRoundPath, Path.Op.DIFFERENCE);
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
mPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
canvas.drawPath(mRectanglePath, mPaint);
mPaint.setXfermode(null);
}
}
運行復現一下
如下圖,左邊是在android9.0以下的效果,中間是android9.0及以上的效果,右邊是想要的效果。中間的只要把藍色改爲Activity背景色就是想要的效果了。
解決辦法:
1.去掉setXfermode
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
canvas.drawPath(mRectanglePath, mPaint);
}
2.使用canvas.saveLayer
//第一種
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
int sc = canvas.saveLayer(0, 0, mViewWidth, mViewHeight, null, Canvas.ALL_SAVE_FLAG);
//去掉setXfermode或者PorterDuff.Mode.SRC_IN改爲PorterDuff.Mode.SRC
//mPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC));
canvas.drawPath(mRectanglePath, mPaint);
mPaint.setXfermode(null);
canvas.restoreToCount(sc);
}
//第二種
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
int sc = canvas.saveLayer(0, 0, mViewWidth, mViewHeight, null, Canvas.ALL_SAVE_FLAG);
//如果不設置canvas.drawColor,只能是去掉setXfermode或者PorterDuff.Mode.SRC_IN改爲PorterDuff.Mode.SRC
canvas.drawColor(Color.RED);
//如果設置了canvas.drawColor,PorterDuffXfermode可以是SRC_IN或者SRC,也可以是DST_IN(但是此時四個角的顏色是canvas.drawColor(XXX)設置的顏色
mPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
canvas.drawPath(mRectanglePath, mPaint);
mPaint.setXfermode(null);
canvas.restoreToCount(sc);
}
但就官方不建議使用該方法,具體可以看官方文檔
3.關閉硬件加速
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
mPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
//關閉硬件加速,如果應用已經關閉的硬件加速設置LAYER_TYPE_HARDWARE和LAYER_TYPE_SOFTWARE效果是相同的
setLayerType(LAYER_TYPE_SOFTWARE, null);
canvas.drawPath(mRectanglePath, mPaint);
mPaint.setXfermode(null);
}
注意:你是無法在視圖級別開啓硬件加速的,如果你的應用已經關閉了硬件加速,那麼設置LAYER_TYPE_HARDWARE和LAYER_TYPE_SOFTWARE 效果是相同的。可以看官方文檔 視圖級別關閉硬件加速 和 hardware layer
爲什麼是黑色的原因,我找了很久也沒找到,如果有知道原因的,希望能告訴我一下,謝謝。