要绘图，首先得调整画笔，待画笔调整好之后，再将图像绘制到画布上，这样才可以显示在手机屏幕上。Android 中的画笔是 Paint类，Paint 中包含了很多方法对其属性进行设置，主要方法如下： 

   setAntiAlias: 设置画笔的锯齿效果。 
   setColor: 设置画笔颜色 
   setARGB:  设置画笔的a,r,p,g值。 
   setAlpha:  设置Alpha值 
   setTextSize: 设置字体尺寸。 
   setStyle:  设置画笔风格，空心或者实心。 
   setStrokeWidth: 设置空心的边框宽度。 
   getColor:  得到画笔的颜色 
   getAlpha:  得到画笔的Alpha值。 

下面是一个简单的示例 来说明这些方法的使用。先来看看运行效果吧。 

PaintView.java类

package com.example.guaguale;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.util.Log;
import android.view.KeyEvent;
import android.view.MotionEvent;
import android.view.View;

public class PaintView extends View implements Runnable {
	public final static String TAG = "PaintView";
	// 声明Paint对象
	private Paint mPaint = null;

	public PaintView(Context context) {
		super(context);
		// 构建对象
		mPaint = new Paint();

		// 开启线程
		new Thread(this).start();
	}

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

		// 设置Paint为无锯齿
		mPaint.setAntiAlias(true);

		// 设置Paint的颜色
		mPaint.setColor(Color.RED);
		mPaint.setColor(Color.BLUE);
		mPaint.setColor(Color.YELLOW);
		mPaint.setColor(Color.GREEN);
		// 同样是设置颜色
		mPaint.setColor(Color.rgb(255, 0, 0));

		// 提取颜色
		Color.red(0xcccccc);

		// 设置paint的颜色和Alpha值(a,r,g,b)
		mPaint.setAlpha(220);

		// 这里可以设置为另外一个paint对象
		// mPaint.set(new Paint());
		// 设置字体的尺寸
		mPaint.setTextSize(14);

		// 设置paint的风格为“空心”
		// 当然也可以设置为"实心"(Paint.Style.FILL)
		mPaint.setStyle(Paint.Style.STROKE);
		mPaint.setColor(Color.RED);
		// 设置“空心”的外框的宽度
		mPaint.setStrokeWidth(5);

		// 绘制一空心个矩形
		canvas.drawRect(100, 20, 140, 20 + 40, mPaint);

		 // 设置风格为实心
		mPaint.setStyle(Paint.Style.FILL);

		mPaint.setColor(Color.YELLOW);

		// 绘制黄色实心矩形
		canvas.drawRect(10, 20, 50, 20 + 40, mPaint); 
	}

	// 触笔事件
	public boolean onTouchEvent(MotionEvent event) {
		return true;
	}

	// 按键按下事件
	public boolean onKeyDown(int keyCode, KeyEvent event) {
		return true;
	}

	// 按键弹起事件
	public boolean onKeyUp(int keyCode, KeyEvent event) {
		return true;
	}

	public boolean onKeyMultiple(int KeyCode, int repeatCount, KeyEvent event) {
		return true;
	}

	@Override
	public void run() {
		while (!Thread.currentThread().isInterrupted()) {
			try {
				Thread.sleep(100);
			} catch (Exception e) {
				Thread.currentThread().interrupt();
			}
			// 更新界面
			postInvalidate();
		}
	}

}

PaintActivity.java

package com.example.guaguale;

import android.app.Activity;
import android.os.Bundle;

public class PaintActivity extends Activity {

	private PaintView paintView;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_paint);
	 
		paintView = new PaintView(this);
	 
	 setContentView(paintView);
	}
}