两个铁球同时落地

最新推荐文章于 2023-03-30 15:39:06 发布

最新推荐文章于 2023-03-30 15:39:06 发布 · 278 阅读

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#Android #OS #Go #thread #UI

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本文介绍了一个模拟伽利略比萨斜塔实验的Android应用案例，通过编程实现两个不同大小铁球的同时下落，展示了如何使用Android系统的绘图和动画功能。

这是一篇"在比萨斜塔上模拟两个铁球同时落地",如下:

[img]http://dl.iteye.com/upload/attachment/365533/9e7dd723-2b14-3dba-b2eb-e0ddb1c8fa00.png[/img]

代码如下:


package com.chaoqun;

import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.PixelFormat;
import android.graphics.PorterDuffXfermode;
import android.graphics.Rect;
import android.graphics.Bitmap.Config;
import android.graphics.Paint.FontMetrics;
import android.graphics.PorterDuff.Mode;
import android.os.Bundle;
import android.os.Handler;
import android.view.Display;
import android.view.Gravity;
import android.view.View;
import android.view.WindowManager;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ImageView;

public class TwoBalls extends Activity {
    /** Called when the activity is first created. */
	protected WindowManager.LayoutParams _windowParams;
	protected WindowManager _windowManager;
	protected static Display _display;
	protected ImageView  _icon01;
	protected ImageView  _icon02;
	private Handler _messageHandler;
	private Button _go;



    @Override
	protected void onDestroy() {
		//清除手工添加的View
		if(_icon01 != null && _windowManager != null) {
    		_windowManager.removeViewImmediate(_icon01);
    		_icon01 = null;
    	}

		if(_icon02 != null && _windowManager != null) {
    		_windowManager.removeViewImmediate(_icon02);
    		_icon02 = null;
    	}
		super.onDestroy();
	}


	@Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        _go =(Button)findViewById(R.id.options_btn);
        _display = ((WindowManager)this.getSystemService(Context.WINDOW_SERVICE)).getDefaultDisplay(); //获取屏幕介质信息
        _messageHandler = new Handler();
        _go.setOnClickListener( new OnClickListener() {

			@Override
			public void onClick(View v) {
				startAnim(genBitMapforAnim("02", 40), _display.getWidth()-100 , 2, (30-40)/2);
				startAnim(genBitMapforAnim("01", 30), _display.getWidth()-150, 1, 0);
				//这里先后有时间差，忽略了,另外UI Thread在消息处理也有时间差，忽略了。
				//要精确模拟，只有自定义View,单独绘制了。
			}

        });

    }




    protected Bitmap genBitMapforAnim(String itemCode, int size) {
    	 String text = itemCode.length() >= 5 ? itemCode.substring(0, 5) : itemCode;
    	 Bitmap result = Bitmap.createBitmap(size*2,size*2, Config.ARGB_8888);
    	 Canvas canvas =  new   Canvas(result);
    	 canvas.drawARGB(0, 0xff, 0, 0);
    	 Paint paint = new Paint();
    	 paint.setAntiAlias(true); //抗锯齿
    	 paint.setFilterBitmap(true);  //透明设置
    	 paint.setColor(Color.RED);
    	 paint.setAlpha(200);
    	 canvas.drawCircle(size/2, size/2, size/2, paint);//绘制半径为size/2的圆
    	 paint.setAlpha(255);
    	 paint.setTextSize(9);
    	 paint.setColor(Color.WHITE);
    	 float textWidth = paint.measureText(text);  //取得字体宽度
    	 FontMetrics fm = paint.getFontMetrics();  
    	 float textHeight = (float)(fm.descent +  fm.ascent) / 2; //取得字体高度

    	 canvas.drawText(text, (size-textWidth) /2.0f,(size-textHeight)/2.0f, paint); //编号


    	 final Rect rect = new Rect(0, 0,size, size);
    	 paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN));
    	 canvas.drawBitmap(result, rect, rect, paint); //生成透明位图
    	 return result;
    }

    protected  void startAnim(final Bitmap bitmap, final int startXLocation, int id, final int offset) {
    	final int startY = 160;

    	final ImageView imageView = new ImageView(this);
    	imageView.setImageBitmap(bitmap);
    	if(_windowParams == null)
    	_windowParams = new WindowManager.LayoutParams();
    	_windowParams.gravity = Gravity.TOP | Gravity.LEFT;  //标示要关注上下，左右位置
    	_windowParams.x =  startXLocation; //起点坐标x
    	_windowParams.y = startY + offset; //起点坐标y, 设置offset是为了保证起始位置在同一高度

    	_windowParams.height = WindowManager.LayoutParams.WRAP_CONTENT;
    	_windowParams.width = WindowManager.LayoutParams.WRAP_CONTENT;
    	_windowParams.flags = WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE
    					| WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE
    					| WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON
    					| WindowManager.LayoutParams.FLAG_LAYOUT_IN_SCREEN;
    	_windowParams.format = PixelFormat.TRANSLUCENT;
    	_windowParams.windowAnimations = 0;

    	if(_windowManager == null)
    	_windowManager = (WindowManager)TwoBalls.this.getSystemService("window"); //获取全局实例WindowManager


    	ImageView icon = id == 1 ? _icon01 : _icon02; 
    	if(icon != null) {
    		_windowManager.removeViewImmediate(icon);  //移除先前的View
    		icon = null;
    	}
    	else {
    		icon = imageView;
    	}

    	_windowManager.addView(icon, _windowParams); //添加View到当前界面 	


    	  final Runnable runnable = new Runnable() {
    		 double t = 0.0d;
     		 final double g = 2.0d; 
    		  public void run() {
    			t++;
    			_windowParams.x =  startXLocation;  //由于WindowManager是单实例,所以这里要记录每个的x坐标
    			_windowParams.y  = startY + offset + (int)(0.5 * g * t * t); //匀加速运动位置计算
    			_windowManager.updateViewLayout(imageView, _windowParams); //更新坐标
    		  }
    	  };

    	 new Thread() {
    		 long lastUpdate = System.currentTimeMillis();
    		 public void run() {
    			 //设置大家都经过同一高度(这里依旧考虑到球的半径不同)
    			 while (_windowParams.y + offset  < _display.getHeight() - 60  && !Thread.interrupted() && !TwoBalls.this.isFinishing()) {
    				  if(System.currentTimeMillis() - lastUpdate >= 100) { //每隔100ms动一下,移动一侦
    					  lastUpdate = System.currentTimeMillis();
    					  _messageHandler.post(runnable);
    				  }


    			 }

    			 if(!bitmap.isRecycled()) 
    				 bitmap.recycle();    

    		 }
    	 }.start();


    }  








}

已打包，有兴趣的看看.