自定义 View：Bitmap 和 Drawable

package com.besmart.components;
import android.content.Context;import android.graphics.Canvas;import android.graphics.drawable.Drawable;import android.util.AttributeSet;import android.view.View;
import androidx.annotation.Nullable;
public class DrawableView extends View {
    Drawable drawable;
    public DrawableView(Context context, @Nullable AttributeSet attrs) {        super(context, attrs);    }
    {        drawable = new MeshDrawable();    }
    @Override    protected void onDraw(Canvas canvas) {        super.onDraw(canvas);        drawable.setBounds(0, 0, (int) Util.dp2px(300), (int) Util.dp2px(300));        drawable.draw(canvas);    }}

package com.besmart.components;
import android.graphics.Canvas;import android.graphics.Color;import android.graphics.ColorFilter;import android.graphics.Paint;import android.graphics.PixelFormat;import android.graphics.Rect;import android.graphics.drawable.Drawable;
import androidx.annotation.NonNull;import androidx.annotation.Nullable;
public class MeshDrawable extends Drawable {    private static final int INTERVAL = (int) Util.dp2px(80);    Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG); // 抗锯齿
    {        paint.setColor(Color.RED);        paint.setStrokeWidth(Util.dp2px(2));    }
    @Override    public void draw(@NonNull Canvas canvas) {        Rect bound = getBounds();        for (int i = 0; i < bound.right; i+=INTERVAL) {            for (int j = 0; j < bound.bottom; j+=INTERVAL) {                canvas.drawLine(bound.left, j, bound.right, j, paint);                canvas.drawLine(i, bound.top, i, bound.bottom, paint);            }        }    }
    @Override    public void setAlpha(int alpha) {        paint.setAlpha(alpha);    }
    @Override    public int getAlpha() {        return paint.getAlpha();    }
    @Override    public void setColorFilter(@Nullable ColorFilter colorFilter) {        paint.setColorFilter(colorFilter);    }
    @Override    public int getOpacity() { // 获取透明度，其实就是 画笔的透明度        return getAlpha() == 0? PixelFormat.TRANSPARENT: // 完全透明                getAlpha() == 0xff? PixelFormat.OPAQUE: // 不透明的                PixelFormat.TRANSLUCENT; // 半透明的    }}