Question

我正在尝试使用底部的对角线切割实现一个imageview，我将用户在我的应用上显示图像。这是我采取的方法

我创建了一个扩展ImageView的自定义类。
然后我重写onDraw方法来绘制形状（这是我不确定我是否正在做正确的事情

我的自定义imageview类

public class DiagonalSquare extends ImageView {

private Context mContext;
Paint paint ;
Path path;

public DiagonalSquare(Context context, AttributeSet attrs) {
    super(context, attrs);
    this.mContext = context;
    setWillNotDraw(false);
    paint = new Paint(Paint.ANTI_ALIAS_FLAG);
}

@Override
protected void onDraw(Canvas canvas) {

    int w = getWidth(), h = getHeight();
    paint.setStrokeWidth(2);
    paint.setColor(Color.WHITE);
    paint.setStyle(Paint.Style.FILL_AND_STROKE);
    paint.setAntiAlias(true);

    path = new Path();
    path.setFillType(Path.FillType.EVEN_ODD);

    path.moveTo(w,h*3/4);
    path.lineTo(w,h);
    path.lineTo(0,h);
    path.close();
    canvas.drawPath(path, paint);
  }
}

这是我最终得到的 - 蓝色部分是imageview。这是

  <com.noel.CustomShape.DiagonalSquare
            android:id="@+id/background_image"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:fitsSystemWindows="true"
            android:scaleType="centerCrop"
            app:layout_collapseMode="parallax"
            android:src="@drawable/bebe" />

Answer 1

您错过了对super.onDraw(canvas);

的来电

Answer 2

除了@Dimezis回答：如果你想对ImageView背景产生透明效果，你必须清除硬件图层类型，并设置Xfermode疼痛，如下例所示：

package com.j2ko.customviews;

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.util.AttributeSet;
import android.widget.ImageView;

public class CustomImageView extends ImageView {
    private Context mContext;
    Paint paint ;
    Path path;

    public CustomImageView(Context context, AttributeSet attrs) {
        super(context, attrs);
        this.mContext = context;
        setWillNotDraw(false);
        //Move to XML if needed
        setBackgroundColor(Color.TRANSPARENT);
        setLayerType(LAYER_TYPE_HARDWARE, null);
        paint = new Paint(Paint.ANTI_ALIAS_FLAG);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        int w = getWidth(), h = getHeight();
        paint.setStrokeWidth(2);
        paint.setColor(Color.WHITE);
        paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));
        paint.setStyle(Paint.Style.FILL_AND_STROKE);
        paint.setAntiAlias(true);

        path = new Path();

        path.setFillType(Path.FillType.EVEN_ODD);

        path.moveTo(w,h*3/4);
        path.lineTo(w,h);
        path.lineTo(0,h);
        path.close();
        canvas.drawPath(path, paint);
    }
}

这将得到以下结果：

自定义ImageView不显示图像

2 个答案: