学习笔记6：图形绘制

先看一下关于bitmap 配置的理解：跳转：关于ARGB_8888、ALPHA_8、ARGB_4444、RGB_565的理解再看一个关于path的几种画法：

arcTo

 用于绘制弧线（实际是截取圆或椭圆的一部分）--> 这个可以画半圆跳转：Android中moveTo、lineTo、quadTo、cubicTo、arcTo详解（实例

一、Android提供了一系列用于二维绘制的APIs，当绘制2D图形时，通常有两种选择：

　　1.在一个View对象中绘制。继承View类，在子类的 onDraw()方法中写入自己定义的绘制代码。

res/values/colors.xml   --> 一些颜色，方便使用

<?xml version="1.0" encoding="utf-8"?>
<resources>
<color name="red">#f00</color>
<color name="green">#0f0</color>
<color name="blue">#0000ff</color>
<color name="black">#000</color>
<color name="blue_light">#33b5e5</color>
<color name="blue_dark">#0099cc</color>
<color name="purple_light">#aa66cc</color>
<color name="purple_dark">#9933cc</color>
<color name="green_light">#99cc00</color>
<color name="green_dark">#669900</color>
<color name="yellow_light">#ffbb33</color>
<color name="yellow_dark">#ff8800</color>
<color name="red_light">#ff4444</color>
<color name="red_dark">#cc0000</color>
</resources>

java/view/MyPaintView.java

package view;

import android.content.Context;
import android.content.res.Resources;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Path;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;

import com.example.administrator.test.R;

/**
* Created by Administrator on 2016/1/8.
*/
public class MyPaintView extends View
{
private Resources myResources;

// 画笔，定义绘制属性
private Paint myPaint;
private Paint mBitmapPaint;

// 绘制路径
private Path myPath;

// 画布及其底层位图
private Bitmap myBitmap;
private Canvas myCanvas;

private float mX, mY;
private static final float TOUCH_TOLERANCE = 4;

// 记录宽度和高度
private int mWidth;
private int mHeight;

public MyPaintView(Context context)
{
super(context);
initialize();
}

public MyPaintView(Context context, AttributeSet attrs, int defStyle)
{
super(context, attrs, defStyle);
initialize();
}

public MyPaintView(Context context, AttributeSet attrs)
{
super(context, attrs);
initialize();
}

/**
* 初始化工作
*/
private void initialize()
{
// Get a reference to our resource table.
myResources = getResources();

// 绘制自由曲线用的画笔
myPaint = new Paint();
myPaint.setAntiAlias(true); //设置是否使用抗锯齿功能，会消耗较大资源，绘制图形速度会变慢。
myPaint.setDither(true);//设定是否使用图像抖动处理，会使绘制出来的图片颜色更加平滑和饱满，图像更加清晰
myPaint.setColor(myResources.getColor(R.color.purple_dark));
myPaint.setStyle(Paint.Style.STROKE);
myPaint.setStrokeJoin(Paint.Join.ROUND); //设置绘制时个图形的结合方式，如平滑效果等，MITER为锐角，ROUND为圆弧,BEVEL结合处为直线
myPaint.setStrokeCap(Paint.Cap.ROUND);//设置画笔为圆形样式  还有个方形 ract样式
myPaint.setStrokeWidth(12);

myPath = new Path();

mBitmapPaint = new Paint(Paint.DITHER_FLAG); //防抖？？

}

@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh)
{
super.onSizeChanged(w, h, oldw, oldh);
mWidth = w;
mHeight = h;
myBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
myCanvas = new Canvas(myBitmap);
}

@Override
public boolean onTouchEvent(MotionEvent event)
{
float x = event.getX();
float y = event.getY();

switch (event.getAction())
{
case MotionEvent.ACTION_DOWN:
touch_start(x, y);
invalidate();
break;
case MotionEvent.ACTION_MOVE:
touch_move(x, y);
invalidate();
break;
case MotionEvent.ACTION_UP:
touch_up();
invalidate();
break;
}
return true;
}

@Override
protected void onDraw(Canvas canvas)
{
super.onDraw(canvas);

// 背景颜色
// canvas.drawColor(getResources().getColor(R.color.blue_dark));

//Bitmap：图片对象，left:偏移左边的位置，top： 偏移顶部的位置
//drawBitmap(Bitmap bitmap, float left, float top, Paint paint)
// 如果不调用这个方法，绘制结束后画布将清空
canvas.drawBitmap(myBitmap, 0, 0, mBitmapPaint);

// 绘制路径
canvas.drawPath(myPath, myPaint);

}

private void touch_start(float x, float y)
{
myPath.reset();
myPath.moveTo(x, y);
mX = x;
mY = y;
}

private void touch_move(float x, float y)
{
float dx = Math.abs(x - mX);
float dy = Math.abs(y - mY);
if (dx >= TOUCH_TOLERANCE || dy >= TOUCH_TOLERANCE)
{
myPath.quadTo(mX, mY, (x + mX) / 2, (y + mY) / 2); //用于绘制圆滑曲线，即贝塞尔曲线。
mX = x;
mY = y;
}
}

private void touch_up()
{
myPath.lineTo(mX, mY);
// commit the pat
ebba
h to our offscreen
// 如果少了这一句，笔触抬起时myPath重置，那么绘制的线将消失
myCanvas.drawPath(myPath, myPaint);
// kill this so we don't double draw
myPath.reset();
}

/**
* 清除整个图像
*/
public void clear()
{
// 清除方法1：重新生成位图
// myBitmap = Bitmap
// .createBitmap(mWidth, mHeight, Bitmap.Config.ARGB_8888);
// myCanvas = new Canvas(myBitmap);

// 清除方法2：将位图清除为白色
myBitmap.eraseColor(myResources.getColor(R.color.white));

// 两种清除方法都必须加上后面这两步：
// 路径重置
myPath.reset();
// 刷新绘制
invalidate();

}

}

activity/DrawPaintActivity.java

public class DrawPaintActivity extends Activity {@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_draw_paint);final MyPaintView myPaintView = (MyPaintView)findViewById(R.id.paintView);findViewById(R.id.btn_clear).setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View view) {myPaintView.clear();}});}}

布局文件

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"android:layout_height="match_parent"tools:context="com.example.administrator.test.DrawPaintActivity"><view.MyPaintViewandroid:layout_width="fill_parent"android:layout_height="fill_parent"android:id="@+id/paintView"/><Buttonandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:id="@+id/btn_clear"android:text="Clear"/></RelativeLayout>

效果：

　　2.直接在画布（Canvas）上绘制。

package com.example.administrator.test;import android.app.Activity;import android.graphics.Bitmap;import android.graphics.Canvas;import android.graphics.Color;import android.graphics.Paint;import android.graphics.Path;import android.graphics.RectF;import android.os.Bundle;import android.view.ViewGroup;import android.widget.ImageView;import android.widget.LinearLayout;public class DrawActivity extends Activity {@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);Bitmap bitmap = Bitmap.createBitmap(getWindowManager().getDefaultDisplay().getWidth(),getWindowManager().getDefaultDisplay().getHeight(),Bitmap.Config.ARGB_8888);Canvas canvas = new Canvas(bitmap); //画布Paint paint = new Paint();//画笔paint.setAlpha(100); //取值范围为0~255，数值越小越透明/*** 风格： paint.setStyle*         STROKE 仅绘形状的轮廓*         FILL   仅填充形状*         FILL_AND_STROKE 填充并绘制形状的轮廓*///1:画一个点//  paint.setStyle(Style.STROKE);不涉及封闭图形，不写此属性ok~paint.setStrokeWidth(10);    //设置线宽paint.setColor(Color.RED);canvas.drawPoint(400, 201, paint);//2，画一条线//  paint.setStyle(Style.STROKE);不涉及封闭图形，不写此属性ok~paint.setStrokeWidth(10);canvas.drawLine(50, 50, 100, 400, paint); //4个参数分别为起点的xy坐标，终点的xy坐标//3，画一个矩形paint.setStyle(Paint.Style.STROKE);paint.setStrokeWidth(10);paint.setColor(Color.BLUE);canvas.drawRect(50, 500, 400, 700, paint);//距离左边，上边，右边和下边的位置距离坐标。//4，画一个椭圆paint.setStyle(Paint.Style.FILL);paint.setStrokeWidth(10);paint.setColor(Color.GREEN);RectF oval = new RectF(50, 500, 400, 700) ;//这4个参数和矩形一样，相当于矩形里面画了一个椭圆canvas.drawOval(oval, paint);//5，画一个圆paint.setStyle(Paint.Style.FILL_AND_STROKE);paint.setStrokeWidth(10);paint.setColor(Color.YELLOW);canvas.drawCircle(550, 600, 100, paint);//参数表示圆心的xy坐标，半经//6,路径：通过路径Path对象paint.setStyle(Paint.Style.STROKE);paint.setStrokeWidth(10);Path path = new Path();path.moveTo(0, 1000);//起始点path.lineTo(100, 800);path.lineTo(200, 1000);path.lineTo(300, 800);path.lineTo(400, 1000);path.lineTo(500, 800);path.lineTo(600, 1000);path.lineTo(700, 800);canvas.drawPath(path, paint);ImageView imageView = new ImageView(this);ViewGroup.LayoutParams p = new ViewGroup.LayoutParams(LinearLayout.LayoutParams.FILL_PARENT,LinearLayout.LayoutParams.FILL_PARENT);imageView.setLayoutParams(p);imageView.setImageBitmap(bitmap);setContentView(imageView);}}