Android应用开发揭秘的第9个程序5_4_canvas修改版和高仿版的源码注释

最新推荐文章于 2024-03-28 21:48:52 发布

翻译最新推荐文章于 2024-03-28 21:48:52 发布 · 676 阅读

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本文介绍了一个具体的Android应用实例，通过使用Canvas API进行图形绘制。包括如何创建自定义视图(GameView)，设置画布背景颜色，实现锯齿消除，旋转画布，绘制矩形等操作。同时展示了如何通过线程不断刷新界面以达到动画效果。

//学会运用画布canvas

Activity01.java

package com.canvas;

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

public class Activity01 extends Activity
{
private GameView mGameView =null;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState)
{
  super.onCreate(savedInstanceState);

  mGameView = new GameView(this);

  setContentView(mGameView);
}
}

GameView.java

package com.canvas;

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

public class GameView extends View implements Runnable
{
/* 声明Paint对象 */
private Paint mPaint = null;

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

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

public void onDraw(Canvas canvas)
{
  super.onDraw(canvas);

  /* 设置画布的颜色 */
  canvas.drawColor(Color.BLACK);

  /* 设置取消锯齿效果 */
  mPaint.setAntiAlias(true);

  /* 设置裁剪区域 */
  //canvas.clipRect(10, 10, 280, 260);

  /* 线锁定画布 */
  canvas.save();
  /* 旋转画布 */
  canvas.rotate(10.0f); //45.0f

  /* 设置颜色及绘制矩形 */
  mPaint.setColor(Color.RED);
  canvas.drawRect(new Rect(15,15,140,70), mPaint);

  /* 解除画布的锁定 */
  canvas.restore();

  /* 设置颜色及绘制另一个矩形 */
  mPaint.setColor(Color.GREEN);
  canvas.drawRect(new Rect(150,75,260,120), 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 false;
}

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

public void run()
{
  while (!Thread.currentThread().isInterrupted())
  {
   try
   {
    Thread.sleep(100);
   }
   catch (InterruptedException e)
   {
    Thread.currentThread().interrupt();
   }
   // 使用postInvalidate可以直接在线程中更新界面
   postInvalidate();
  }
}
}

Gf_canvasActivity.java

package pak.canvas;

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

public class Gf_canvasActivity extends Activity {
private GameView mGameView =null;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState)
{
  super.onCreate(savedInstanceState);

  mGameView = new GameView(this);

  setContentView(mGameView);
}
}