Android刮刮卡实现原理与代码讲解

 public class GuaGuaLe extends View{ /**中奖文本变量*/ private String mText;//显示文本 private Paint mTextPaint;//绘制文本的画笔 private Rect mTextBounds;//文本的边界 public GuaGuaLe(Context context) { this(context, null); } public GuaGuaLe(Context context, AttributeSet attrs) { super(context, attrs); initView(); } /**初始化一些实例变量*/ private void initView() { setTextMessage();//实例化文本的一些变量 } private void setTextMessage() { mText = "谢谢惠顾"; mTextBounds = new Rect(); mTextPaint = new Paint(); mTextPaint.setAntiAlias(true); mTextPaint.setColor(Color.DKGRAY); mTextPaint.setTextSize(22); mTextPaint.getTextBounds(mText,0,mText.length(),mTextBounds);//获取到绘制文本的长宽 } @Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { super.onMeasure(widthMeasureSpec, heightMeasureSpec); } @Override protected void onDraw(Canvas canvas) { //绘制文本 canvas.drawText(mText,getWidth()/2 - mTextBounds.width()/2,getHeight()/2 + mTextBounds.height()/2,mTextPaint); }}

 /**画板变量*/ private Canvas mCanvas;//缓冲画板 private Bitmap mLayerBimtap;//图层图片 private Bitmap mBitmap;//画板上的画纸 private Paint mPaint;//画笔 @Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { super.onMeasure(widthMeasureSpec, heightMeasureSpec); setCanvasMessage(getMeasuredWidth(),getMeasuredHeight());//实例化缓存画板的一些变量 } /*** * 双缓冲技术 * 1.创建一个与屏幕绘制区域一致的Canvas对象 * 2.先将图形绘制到内存中 * 3.再一次性将对象上的图形拷贝到屏幕上 * @param width * @param height */ private void setCanvasMessage(int width,int height) { mPaint = new Paint(); mPaint.setAntiAlias(true); mPaint.setStyle(Paint.Style.FILL); mPaint.setStrokeWidth(3); mPaint.setColor(Color.parseColor("#c0c0c0")); mBitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);//创建一个空白的位图 mCanvas = new Canvas(mBitmap);//在此Bitmap上作画 //mCanvas.drawColor(Color.parseColor("#c0c0c0"));//绘制背景颜色 mCanvas.drawRoundRect(new RectF(0, 0, width, height), 20, 20, mPaint);//绘制圆角矩形 mLayerBimtap = BitmapFactory.decodeResource(getResources(), R.mipmap.fg_guaguaka); mCanvas.drawBitmap(mLayerBimtap, null, new RectF(0, 0, width, height), null);//绘制图层图片 @Override protected void onDraw(Canvas canvas) { //绘制文本 canvas.drawText(mText,getWidth()/2 - mTextBounds.width()/2,getHeight()/2 + mTextBounds.height()/2,mTextPaint); //绘制图层 //canvas.drawBitmap(mBitmap,0,0,null); //绘制图层图片 canvas.drawBitmap(mBitmap,0,0,null); } }

 /**路径变量*/ private Path mPath; private Paint mPathPaint; private int mLastX;//记录上一次X坐标 private int mLastY;//记录上一次Y坐标 /**初始化一些实例变量*/ private void initView() { setTextMessage();//实例化文本的一些变量 setPathMessage();//实例化路径的一些变量 } @Override public boolean onTouchEvent(MotionEvent event) { int action = event.getAction(); //获取手指在屏幕上的坐标 int x = (int) event.getX(); int y = (int) event.getY(); switch (action){  case MotionEvent.ACTION_DOWN:  mLastX = x;  mLastY = y;  mPath.moveTo(mLastX,mLastY);  break;  case MotionEvent.ACTION_MOVE:  int dx = Math.abs(x - mLastX);  int dy = Math.abs(y - mLastY);  if(dx > 3 || dy >3){   mPath.lineTo(x, y);  }  mLastX = x;  mLastY = y;  break;  case MotionEvent.ACTION_UP:  break;  default:  break; } invalidate();//主线程中刷新 return true;//截取事件向下分发 } @Override protected void onDraw(Canvas canvas) { //绘制文本 canvas.drawText(mText,getWidth()/2 - mTextBounds.width()/2,getHeight()/2 + mTextBounds.height()/2,mTextPaint); //绘制路径 drawPath(); //绘制图片【图层背景颜色】 //canvas.drawBitmap(mBitmap,0,0,null); //绘制图片【图层图片】 canvas.drawBitmap(mBitmap, 0, 0, null); } //返回给系统的canvas是一幅带有路径的位图 private void drawPath() { //这之前是设置了图层图片 mPathPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.DST_OUT)); mCanvas.drawPath(mPath,mPathPaint); }

 /**擦除是否完成*/ private volatile boolean isComplete; /**回调接口*/ private OnCompleteListener mOnCompleteListener; public interface OnCompleteListener{ void complete(); } //对外设置调用的公开方法 public void setmOnCompleteListener(OnCompleteListener mOnCompleteListener){ this.mOnCompleteListener = mOnCompleteListener; } case MotionEvent.ACTION_UP:  //开启一个线程去计算擦除的面积  new Thread(new Runnable() {   @Override   public void run() {   int width = getWidth();   int height = getHeight();   int area = 0;//记录被擦数的范围大小   int percent ;   for(int i=0;i<width;i++)    for(int j = 0;j<height;j++){    if(mBitmap.getPixel(i,j) == 0){     area ++;    }    }   if(area > 0){    percent = area *100/(width*height);    if(percent > 20){    isComplete = true;    postInvalidate();//在子线程中刷新，可能比较耗时操作    }   }   }  }).start(); @Override protected void onDraw(Canvas canvas) { //绘制文本 canvas.drawText(mText, getWidth() / 2 - mTextBounds.width() / 2, getHeight() / 2 + mTextBounds.height() / 2, mTextPaint); if(isComplete){  if(mOnCompleteListener != null){  mOnCompleteListener.complete();//接口回调，在主线程中  } } if(!isComplete){  //绘制路径  drawPath();  //绘制图片【图层背景颜色】  //canvas.drawBitmap(mBitmap,0,0,null);  //绘制图片【图层图片】  canvas.drawBitmap(mBitmap, 0, 0, null); } }public class MainActivity extends AppCompatActivity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); GuaGuaLe guaguaLeView = (GuaGuaLe) findViewById(R.id.guaguale); //注册了一个观察者 guaguaLeView.setmOnCompleteListener(new GuaGuaLe.OnCompleteListener() {  @Override  public void complete() {  Toast.makeText(MainActivity.this, "用户绘制了大部分", Toast.LENGTH_SHORT).show();  } }); }}

在values/attrs.xml中定义 <declare-styleable name="GuaGuaLe"> <attr name="text" format="string"></attr> <attr name="textSize" format="dimension"></attr> <attr name="textColor" format="color"></attr> </declare-styleable>在布局文件中定义属性 <zlll.bg.com.example.cn.myapplication.view.GuaGuaLe  android:id="@+id/guaguale"  android:layout_width="350dp"  android:layout_height="200dp"  app:text="$5,000"  app:textColor="#c02040"  app:textSize="22sp"  android:layout_centerInParent="true"/>在主界面中定义Text文本public class MainActivity extends AppCompatActivity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); GuaGuaLe guaguaLeView = (GuaGuaLe) findViewById(R.id.guaguale); //注册了一个观察者 guaguaLeView.setmOnCompleteListener(new GuaGuaLe.OnCompleteListener() {  @Override  public void complete() {  Toast.makeText(MainActivity.this, "用户绘制了大部分", Toast.LENGTH_SHORT).show();  } }); guaguaLeView.setTextByUser("Android 新技能Get"); }} /**中奖文本变量*/ private String mText;//显示文本 private Paint mTextPaint;//绘制文本的画笔 private Rect mTextBounds;//文本的边界 //以下两个是新增的 private int mTextSize;//文本大小 private int mTextColor;//文本颜色 //对外设置调用的设置文本公开方法 public void setTextByUser(String text){ mText = text; mTextPaint.getTextBounds(mText,0,mText.length(),mTextBounds);//重新计算文本的范围 }在构造函数中定义 public GuaGuaLe(Context context, AttributeSet attrs) { super(context, attrs); //获取自定义属性的值 TypedArray a = context.obtainStyledAttributes(attrs,R.styleable.GuaGuaLe); mText = a.getString(R.styleable.GuaGuaLe_text); mTextColor = a.getColor(R.styleable.GuaGuaLe_textColor, Color.parseColor("#c0c0c0")); //TypedValue.applyDimension内部就是将sp,dp转化为px mTextSize = a.getDimensionPixelSize(R.styleable.GuaGuaLe_textSize, (int) TypedValue.applyDimension  (TypedValue.COMPLEX_UNIT_SP,22,getResources().getDisplayMetrics())); a.recycle(); initView(); }