mysurfaceview.java

来自「Android开发精典案例60个」· Java 代码 · 共 168 行

package com.mcp;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.view.KeyEvent;
import android.view.MotionEvent;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.SurfaceHolder.Callback;

/**
 * 
 * @author Himi
 *
 */
public class MySurfaceView extends SurfaceView implements Callback, Runnable {
	private SurfaceHolder sfh;
	private Paint paint;
	private Thread th;
	private boolean flag;
	private Canvas canvas;
	private int screenW, screenH;
	//声明一张icon位图
	private Bitmap bmpIcon;
	//记录两个触屏点的坐标
	private int x1, x2, y1, y2;
	//倍率
	private float rate = 1;
	//记录上次的倍率
	private float oldRate = 1;
	//记录第一次触屏时线段的长度
	private float oldLineDistance;
	//判定是否头次多指触点屏幕
	private boolean isFirst = true;

	/**
	 * SurfaceView初始化函数
	 */
	public MySurfaceView(Context context) {
		super(context);
		sfh = this.getHolder();
		sfh.addCallback(this);
		paint = new Paint();
		paint.setAntiAlias(true);
		setFocusable(true);
		bmpIcon = BitmapFactory.decodeResource(this.getResources(), R.drawable.icon);
	}

	/**
	 * SurfaceView视图创建，响应此函数
	 */
	@Override
	public void surfaceCreated(SurfaceHolder holder) {
		screenW = this.getWidth();
		screenH = this.getHeight();
		flag = true;
		//实例线程
		th = new Thread(this);
		//启动线程
		th.start();
	}

	/**
	 * 游戏绘图
	 */
	public void myDraw() {
		try {
			canvas = sfh.lockCanvas();
			if (canvas != null) {
				canvas.drawColor(Color.WHITE);
				canvas.save();
				//缩放画布(以图片中心点进行缩放，XY轴缩放比例相同)
				canvas.scale(rate, rate, screenW / 2, screenH / 2);
				//绘制位图icon
				canvas.drawBitmap(bmpIcon, screenW / 2 - bmpIcon.getWidth() / 2, screenH / 2 - bmpIcon.getHeight() / 2, paint);
				canvas.restore();
				//便于观察，这里绘制两个触点时形成的线段
				canvas.drawLine(x1, y1, x2, y2, paint);
			}
		} catch (Exception e) {
			// TODO: handle exception
		} finally {
			if (canvas != null)
				sfh.unlockCanvasAndPost(canvas);
		}
	}

	/**
	 * 触屏事件监听
	 */
	@Override
public boolean onTouchEvent(MotionEvent event) {
	//用户手指抬起默认还原为第一次触屏标识位，并且保存本次的缩放比例
	if (event.getAction() == MotionEvent.ACTION_UP) {
		isFirst = true;
		oldRate = rate;
	} else {
		x1 = (int) event.getX(0);
		y1 = (int) event.getY(0);
		x2 = (int) event.getX(1);
		y2 = (int) event.getY(1);
		if (event.getPointerCount() == 2) {
			if (isFirst) {
				//得到第一次触屏时线段的长度
				oldLineDistance = (float) Math.sqrt(Math.pow(event.getX(1) - event.getX(0), 2) + Math.pow(event.getY(1) - event.getY(0), 2));
				isFirst = false;
			} else {
				//得到非第一次触屏时线段的长度
				float newLineDistance = (float) Math.sqrt(Math.pow(event.getX(1) - event.getX(0), 2) + Math.pow(event.getY(1) - event.getY(0), 2));
				//获取本次的缩放比例
				rate = oldRate * newLineDistance / oldLineDistance;
			}
		}
	}
	return true;
}

	/**
	 * 按键事件监听
	 */
	@Override
	public boolean onKeyDown(int keyCode, KeyEvent event) {
		return super.onKeyDown(keyCode, event);
	}

	/**
	 * 游戏逻辑
	 */
	private void logic() {
	}

	@Override
	public void run() {
		while (flag) {
			long start = System.currentTimeMillis();
			myDraw();
			logic();
			long end = System.currentTimeMillis();
			try {
				if (end - start < 50) {
					Thread.sleep(50 - (end - start));
				}
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
		}
	}

	/**
	 * SurfaceView视图状态发生改变，响应此函数
	 */
	@Override
	public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
	}

	/**
	 * SurfaceView视图消亡时，响应此函数
	 */
	@Override
	public void surfaceDestroyed(SurfaceHolder holder) {
		flag = false;
	}
}