Android的2D画图（一）

Android SDK支持基本的2D绘图。这一节比较简单，但是要按照自己的想法实现自己想要的目标图还是有一点困难的，这个要到项目开发实际问题中方能见到它的美妙之处。此处给出一个例子看一下注释就明白了。

package mobile.android.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 };@Overridepublic 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);}//扩展多条直线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);}@Overrideprotected void onDraw(Canvas canvas){//绘制像素点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);//绘制直线canvas.drawLine(10, 10, 300, 10, paint1);canvas.drawLine(10, 30, 300, 30, paint2);canvas.drawLine(10, 50, 300, 50, paint3);//绘制正方形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);//绘制三角形drawLinesExt(canvas, new float[]{ 160, 70, 230, 150, 170, 155, 160, 70 }, paint2);//设置非填充状态paint2.setStyle(Style.STROKE);//画空心圆canvas.drawCircle(260, 110, 40, paint2);//设置填充状态paint2.setStyle(Style.FILL);//画实心圆canvas.drawCircle(260, 110, 30, paint2);RectF rectF = new RectF();rectF.left = 30;rectF.top = 190;rectF.right = 120;rectF.bottom = 280;//画弧canvas.drawArc(rectF, 0, 200, useCenter, paint2);rectF.left = 140;rectF.top = 190;rectF.right = 280;rectF.bottom = 290;paint2.setStyle(Style.STROKE);//画空心椭圆canvas.drawArc(rectF, 0, 360, useCenter, paint2);rectF.left = 160;rectF.top = 190;rectF.right = 260;rectF.bottom = 290;paint3.setStyle(Style.STROKE);//画空心圆canvas.drawArc(rectF, 0, 360, useCenter, paint3);float y = 0;//绘制文本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);canvas.drawPosText("圆形", new float[]{180,230, 210,250}, paint1);}}@Overridepublic void onCreate(Bundle savedInstanceState){super.onCreate(savedInstanceState);//装载视图setContentView(new MyView(this));}}

上面写了一些注释，一目了然就可以知道怎么做了！！