Android 使用View类绘图

View类是Android的一个超类，这个类几乎包含了所有的屏幕类型，每一个View都有一个用户绘画的画布。任何一个View类都只要重写onDraw方法来实现界面显示。

package com.Aina.Android;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.view.View;

public class ImageView extends View {

	public static int x = 20;
	public static int y = 20;
	
	public ImageView(Context context) {
		super(context);
	}

	/**
	 * 绘制方法.
	 */
	@Override
	protected void onDraw(Canvas canvas) {
		super.onDraw(canvas);
		Paint paint = new Paint();
		paint.setColor(Color.RED);//设置颜色
		canvas.drawRect(x, y, x+40, y+40, paint);//绘制一个矩形
	}

}

package com.Aina.Android;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.KeyEvent;
import android.view.MotionEvent;
import android.view.Window;
import android.view.WindowManager;
import android.util.DisplayMetrics;
import android.util.Log;

public class Test_View extends Activity {
	/** Called when the activity is first created. */
	private ImageView iv = null;
	private static final int MSG = 0x0000001;
	private int DisplayWidth = 0, DisplayHeight = 0;

	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		//隐藏标题栏和状态栏也可以设置主题（Theme）在AndridManifest.xml里面设置：android:theme="@android:style/Theme.Black.NoTitleBar.Fullscreen"
		Window window = this.getWindow();
		window.setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
				WindowManager.LayoutParams.FLAG_FULLSCREEN);//隐藏状态栏
		this.requestWindowFeature(Window.FEATURE_NO_TITLE);//隐藏标题栏
		
		iv = new ImageView(this);
		setContentView(iv);
		// 获得屏幕宽带和高度
		DisplayMetrics dm = new DisplayMetrics();
		this.getWindowManager().getDefaultDisplay().getMetrics(dm);
		DisplayWidth = dm.widthPixels;// 屏幕宽带
		DisplayHeight = dm.heightPixels;// 屏幕高度

		MyThread th = new MyThread();
		th.start();
	}

	private Handler handle = new Handler() {
		public void handleMessage(Message msg) {
			super.handleMessage(msg);
			if (msg.what == MSG) {
				iv.invalidate();// 更新界面
			}
		}
	};

	class MyThread extends Thread {
		public void run() {
			while (!Thread.currentThread().isInterrupted()) {// 当前线程没有中断
				try {
					Message msg = new Message();
					msg.what = MSG;
					Test_View.this.handle.sendMessage(msg);// 发送消息
					Thread.sleep(100);
				} catch (Exception ex) {
					ex.printStackTrace();
					Thread.currentThread().interrupt();// 中断当前线程.
				}

			}
		}
	}

	/*使用postInvalidate()方法更新界面，可以直接在线程里面更新。
	 * class MyThread extends Thread { public void run() { while
	 * (!Thread.currentThread().isInterrupted()) {// 当前线程没有中断 try {
	 * Thread.sleep(100); iv.postInvalidate(); } catch (Exception ex) {
	 * ex.printStackTrace(); Thread.currentThread().interrupt();// 中断当前线程. } } }
	 * }
	 */
	/**
	 * 触笔事件
	 */
	@Override
	public boolean onTouchEvent(MotionEvent event) {
				int x = (int) event.getX();
		int y = (int) event.getY();
		ImageView.x = x;
		ImageView.y=y;
		Log.d("EVENT", x+"|"+y);
		return super.onTouchEvent(event);
	}

	/**
	 * 键盘按下事件
	 */
	@Override
	public boolean onKeyDown(int keyCode, KeyEvent event) {
		switch (keyCode) {
		case KeyEvent.KEYCODE_DPAD_DOWN:// 向下
			Log.d("y", ImageView.y + "");
			if (ImageView.y + 40 >= DisplayHeight) {
				ImageView.y = DisplayHeight - 40;
			} else {
				ImageView.y += 5;
			}
			break;
		case KeyEvent.KEYCODE_DPAD_UP:// 向上
			if (ImageView.y <= 0) {
				ImageView.y = 0;
			} else {
				ImageView.y -= 5;
			}
			break;
		case KeyEvent.KEYCODE_DPAD_LEFT:// 向左
			if (ImageView.x <= 0) {
				ImageView.x = 0;
			} else {
				ImageView.x -= 5;
			}
			break;
		case KeyEvent.KEYCODE_DPAD_RIGHT:// 向右
			if (ImageView.x + 40 >= DisplayWidth) {
				ImageView.x = DisplayWidth - 40;
			} else {
				ImageView.x += 5;
			}
			break;
		default:
			break;
		}
		return super.onKeyDown(keyCode, event);
	}

	/**
	 * 键盘按下之后弹起事件
	 */
	@Override
	public boolean onKeyUp(int keyCode, KeyEvent event) {

		return super.onKeyUp(keyCode, event);
	}

}