安卓突击：绘制图形和文本

drawPointdrawLinedrawCircledrawArcdrawText
创建一个类继承于View首先创建一个Paint对象，给这个Paint对象设置线的颜色，大小等风格。然后在onDraw方法里，通过Canvas对象来调用划线函数，最后一个参数是paint对象。invalidate（）方法是：让屏幕刷新一次。即是将所有的图形都抹掉，重新画。在画弧线的时候，可以设置是不是选择经过圆心。
在Activity的onCreate的方法里，setContentView（）函数里的参数是new 一个视图的对象。下面这个例子是，点击一次屏幕，重新绘制一遍屏幕上的线或者字。其中有一个是画扇形的时候不经过圆心，有一个是经过的。

package cn.eoe.draw;

import android.app.Activity;

import android.content.Context;

import android.graphics.Canvas;

import android.graphics.Color;

import android.graphics.Paint;

import android.graphics.RectF;

import android.graphics.Paint.Style;

import android.os.Bundle;

import android.view.MotionEvent;

import android.view.View;

public class Main extends Activity

{

class MyView extends View

{

private Paint paint1 = new Paint();

private Paint paint2 = new Paint();

private Paint paint3 = new Paint();

private boolean useCenter = true;

private float[] textSizeArray = new float[]

{ 15, 18, 21, 24, 27 };

@Override

public boolean onTouchEvent(MotionEvent event)

{

if (useCenter)

{

useCenter = false;

paint1.setColor(Color.RED);

paint2.setColor(Color.BLACK);

paint3.setColor(Color.GREEN);

paint1.setStrokeWidth(6);

paint2.setStrokeWidth(4);

paint3.setStrokeWidth(2);

}

else

{

useCenter = true;

paint1.setColor(Color.BLACK);

paint2.setColor(Color.RED);

paint3.setColor(Color.BLUE);

paint1.setStrokeWidth(2);

paint2.setStrokeWidth(4);

paint3.setStrokeWidth(6);

}

for (int i = 0; i < textSizeArray.length / 2; i++)

{

float textSize = textSizeArray[i];

textSizeArray[i] = textSizeArray[textSizeArray.length - i - 1];

textSizeArray[textSizeArray.length - i - 1] = textSize;

}

invalidate();

return super.onTouchEvent(event);

}

public MyView(Context context)

{

super(context);

setBackgroundColor(Color.WHITE);

paint1.setColor(Color.BLACK);

paint1.setStrokeWidth(2);

paint2.setColor(Color.RED);

paint2.setStrokeWidth(4);

paint3.setColor(Color.BLUE);

paint3.setStrokeWidth(6);

}

private void drawLinesExt(Canvas canvas, float[] pts, Paint paint)

{

float[] points = new float[pts.length * 2 - 4];

for (int i = 0, j = 0; i < pts.length; i = i + 2)

{

points[j++] = pts[i];

points[j++] = pts[i + 1];

if (i > 1 && i < pts.length - 2)

{

	points[j++] = pts[i];

	points[j++] = pts[i + 1];

}

}

canvas.drawLines(points, paint);

}

@Override

protected void onDraw(Canvas canvas)

{

canvas.drawPoint(60, 120, paint3);

canvas.drawPoint(70, 130, paint3);

canvas.drawPoints(new float[]

{ 70, 140, 75, 145, 75, 160 }, paint2);

//canvas.drawPoints(new float[]

  //              { 70, 140, 75, 145, 75, 160 }, 1,4,paint2);

canvas.drawLine(10, 10, 300, 10, paint1);

canvas.drawLine(10, 30, 300, 30, paint2);

canvas.drawLine(10, 50, 300, 50, paint3);

drawLinesExt(canvas, new float[]

{ 10, 70, 120, 70, 120, 170, 10, 170, 10, 70 }, paint2);

drawLinesExt(canvas, new float[]

{ 25, 85, 105, 85, 105, 155, 25, 155, 25, 85 }, paint3);

drawLinesExt(canvas, new float[]

{ 160, 70, 230, 150, 170, 155, 160, 70 }, paint2);

paint2.setStyle(Style.STROKE);

canvas.drawCircle(260, 110, 40, paint2);

paint2.setStyle(Style.FILL);

canvas.drawCircle(260, 110, 30, paint2);

RectF rectF = new RectF();

rectF.left = 30;

rectF.top = 190;

rectF.right = 120;

rectF.bottom = 280;

canvas.drawArc(rectF, 0, 200, useCenter, paint2);

rectF.left = 140;

rectF.top = 190;

rectF.right = 280;

rectF.bottom = 290;

paint2.setStyle(Style.STROKE);

canvas.drawArc(rectF, 0, 360, useCenter, paint2);

rectF.left = 160;

rectF.top = 190;

rectF.right = 260;

rectF.bottom = 290;

paint3.setStyle(Style.STROKE);

canvas.drawArc(rectF, 0, 360, useCenter, paint3);

float y = 0;

for (int i = 0; i < textSizeArray.length; i++)

{

	paint1.setTextSize(textSizeArray[i]);

	paint1.setColor(Color.BLUE);

	canvas.drawText("Android（宽度：" + paint1.measureText("Android")

+ "）", 20, 315 + y, paint1);

	y += paint1.getTextSize() + 5;

}

paint1.setTextSize(22);

}

}

@Override

public void onCreate(Bundle savedInstanceState)

{

super.onCreate(savedInstanceState);

setContentView(new MyView(this));

}

}

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来自为知笔记(Wiz)