平台
RK3399 + Android 8.1
问题
代码中, 屏幕分辨率为1024x600, 自定义View的尺寸为300x300, 在窗口居中显示.
自定义View绘制的顺序为:
绘制白色背景-Canvas.drawColor
绘制黑色矩形-Canvas.drawRect
绘制红色交叉线, 分别为左上-右下 和 右上-左下 两条
绘制四个角圆, 半径为10个像素
效果图:
在代码中,增加了左右拖动旋转控件的功能
上图的虚线, 非代码绘制
在没有旋转控件前, 并未出现图中的虚线, 而且虚线还会根据旋转的角度而产生变化, 虚线的颜色会根据自定义View的背景色发生改变.
源码
canvas_test.xml
<?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:id="@+id/rlRoot" android:background="#FF000000"/>
CanvasTest.java
package com.android.test; import android.content.Context; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import android.graphics.RectF; import android.os.Bundle; import android.view.MotionEvent; import android.view.View; import android.widget.RelativeLayout; import com.android.test.R; public class CanvasTest extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.canvas_test); RelativeLayout rlRoot = (RelativeLayout)findViewById(R.id.rlRoot); CanvasView cv = new CanvasView(this); RelativeLayout.LayoutParams lp = new RelativeLayout.LayoutParams(300, 300); lp.addRule(RelativeLayout.CENTER_IN_PARENT); rlRoot.addView(cv, lp); } class CanvasView extends View { Paint p_anti = new Paint(Paint.ANTI_ALIAS_FLAG); Paint p_norm = new Paint(); public CanvasView(Context context) { super(context); } int W, H; int CX, CY; RectF viewPort = new RectF(); @Override protected void onSizeChanged(int w, int h, int oldw, int oldh) { super.onSizeChanged(w, h, oldw, oldh); W = w; CX = W/2; H = h; CY = H/2; viewPort.set(0, 0, W, H); } float dx, dy, cx, cy; float rotZ = 0; @Override public boolean onTouchEvent(MotionEvent event) { float x = event.getRawX(); float y = event.getRawY(); cx = x; cy = y; switch(event.getAction()){ case MotionEvent.ACTION_DOWN: dx = x; dy = y; rotZ = getRotation(); break; case MotionEvent.ACTION_MOVE: float rotate = (dx - cx) / W; setRotation(rotZ + 90f * rotate); break; } return true; } @Override protected void onDraw(Canvas canvas) { Paint p = p_anti; canvas.drawColor(Color.WHITE); //RECT p.setColor(Color.BLACK); canvas.drawRect(viewPort, p); //LINES p.setColor(Color.RED); float[] lines = {viewPort.left, viewPort.top, viewPort.right, viewPort.bottom, viewPort.right, viewPort.top, viewPort.left, viewPort.bottom}; canvas.drawLines(lines, p); //CIRCLE for(int i = 0; i < lines.length / 2; i ++){ canvas.drawCircle(lines[i * 2], lines[i * 2 + 1], 10, p); } } } }
最终发现, 这是由Paint引起的.
在代码中定义了两个Paint
Paint p_anti = new Paint(Paint.ANTI_ALIAS_FLAG); Paint p_norm = new Paint();
在onDraw函数中, 使用p_norm并不会出现虚线的问题, 而使用p_anti才会出现.
放大图像:
