下面我将详细讲解“Android刮刮卡效果实现代码”的完整攻略。
1. 刮刮卡效果的原理
刮刮卡效果的实现原理是在一个遮罩层上绘制一张不透明的灰色图片,在用户拖动时,用透明的颜色替换遮罩层上的灰色颜色,从而显示出下面的图片。
2. 实现步骤
Step 1:设计布局
首先,需要在布局文件中添加一个自定义View,用于实现刮刮卡效果。
<com.example.scratchcard.ScratchCardView
android:id="@+id/scratch_card_view"
android:layout_width="match_parent"
android:layout_height="match_parent" />
Step 2:在ScratchCardView类中实现刮刮卡效果
在ScratchCardView类中实现刮刮卡的效果,需要重写onDraw()、onTouchEvent()方法。
public class ScratchCardView extends View {
//遮罩层Bitmap
private Bitmap mMaskBitmap;
//遮罩层画布
private Canvas mMaskCanvas;
private Paint mMaskPaint;
//底图Bitmap
private Bitmap mBitmap;
//底图画布
private Canvas mCanvas;
private Paint mBitmapPaint;
//手指移动时的起点
private float mLastX, mLastY;
//遮罩颜色
private int mMaskColor = 0xFF9E9E9E;
//刮开的面积占总面积的比例
private float mScratchPercent = 0.5f;
//刮开后的回调接口
private OnScratchCompleteListener mListener;
public ScratchCardView(Context context) {
super(context);
}
public ScratchCardView(Context context, AttributeSet attrs) {
super(context, attrs);
}
public ScratchCardView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
}
@Override
protected void onDraw(Canvas canvas) {
canvas.drawBitmap(mBitmap, 0, 0, null);
canvas.drawBitmap(mMaskBitmap, 0, 0, mMaskPaint);
}
@Override
public boolean onTouchEvent(MotionEvent event) {
int action = event.getAction();
switch (action) {
case MotionEvent.ACTION_DOWN:
mLastX = event.getX();
mLastY = event.getY();
break;
case MotionEvent.ACTION_MOVE:
float x = event.getX();
float y = event.getY();
//在两个点之间绘制一条线,画笔采用SRC_OUT模式
mMaskCanvas.drawLine(mLastX, mLastY, x, y, mMaskPaint);
mLastX = x;
mLastY = y;
//计算刮开的面积占总面积的比例
float scratchArea = getScratchArea();
if (scratchArea > mScratchPercent) {
if (mListener != null) {
mListener.onScratchComplete(this);
}
}
invalidate();
break;
}
return true;
}
/**
* 获取刮开的面积占总面积的比例
*/
private float getScratchArea() {
int width = getWidth();
int height = getHeight();
int[] pixels = new int[width * height];
mMaskBitmap.getPixels(pixels, 0, width, 0, 0, width, height);
int count = 0;
for (int i = 0; i < pixels.length; i++) {
if (pixels[i] == 0) {
count++;
}
}
return (float) count / (float) (width * height);
}
/**
* 初始化画笔
*/
private void initPaint() {
mMaskPaint = new Paint();
mMaskPaint.setAntiAlias(true);
mMaskPaint.setStrokeWidth(50f);
mMaskPaint.setStyle(Paint.Style.STROKE);
mMaskPaint.setStrokeJoin(Paint.Join.ROUND);
mMaskPaint.setStrokeCap(Paint.Cap.ROUND);
mMaskPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_OUT));
mBitmapPaint = new Paint();
mBitmapPaint.setAntiAlias(true);
mBitmapPaint.setStrokeWidth(50f);
mBitmapPaint.setStyle(Paint.Style.STROKE);
mBitmapPaint.setStrokeJoin(Paint.Join.ROUND);
mBitmapPaint.setStrokeCap(Paint.Cap.ROUND);
mBitmapPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_OVER));
}
/**
* 初始化Bitmap和Canvas
*/
private void initBitmapAndCanvas() {
int width = getWidth();
int height = getHeight();
//初始化遮罩层Bitmap和Canvas
mMaskBitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
mMaskCanvas = new Canvas(mMaskBitmap);
mMaskCanvas.drawColor(mMaskColor);
//初始化底图Bitmap和Canvas
mBitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
mCanvas = new Canvas(mBitmap);
}
/**
* 初始化ScratchCardView
*/
public void init() {
initPaint();
initBitmapAndCanvas();
}
/**
* 设置遮罩层的颜色
*/
public void setMaskColor(int color) {
mMaskColor = color;
}
/**
* 设置刮开的面积占总面积的比例
*/
public void setScratchPercent(float percent) {
mScratchPercent = percent;
}
/**
* 设置刮开后的回调接口
*/
public void setOnScratchCompleteListener(OnScratchCompleteListener listener) {
mListener = listener;
}
/**
* 获取底图Bitmap
*/
public Bitmap getBitmap() {
return mBitmap;
}
/**
* 清除ScratchCardView的内容
*/
public void clear() {
mMaskCanvas.drawColor(mMaskColor, PorterDuff.Mode.CLEAR);
mCanvas.drawColor(Color.TRANSPARENT, PorterDuff.Mode.CLEAR);
invalidate();
}
/**
* 刮开后的回调接口
*/
public interface OnScratchCompleteListener {
void onScratchComplete(View view);
}
}
Step 3:使用ScratchCardView实现自定义的刮刮卡效果
public class MainActivity extends AppCompatActivity implements ScratchCardView.OnScratchCompleteListener {
private ScratchCardView mScratchCardView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mScratchCardView = findViewById(R.id.scratch_card_view);
mScratchCardView.setScratchPercent(0.5f);
mScratchCardView.setMaskColor(0xFF9E9E9E);
mScratchCardView.setOnScratchCompleteListener(this);
mScratchCardView.init();
Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.pic);
mScratchCardView.getBitmap().drawBitmap(bitmap, null,
new Rect(0, 0, mScratchCardView.getWidth(), mScratchCardView.getHeight()), mScratchCardView.mBitmapPaint);
mScratchCardView.invalidate();
}
@Override
public void onScratchComplete(View view) {
Toast.makeText(this, "刮开了一半", Toast.LENGTH_SHORT).show();
}
}
3. 示例说明
示例一:
在上面的代码中,我们添加了一个自定义View,实现了刮刮卡效果,定义了遮罩层Bitmap、遮罩层画布、底图Bitmap、底图画布、手指移动的起点、遮罩颜色、刮开的面积占总面积的比例、刮开后的回调接口,并在ScratchCardView类中重写了onDraw()、onTouchEvent()方法。
示例二:
在MainActivity中,我们初始化了ScratchCardView,设置了刮开的面积占总面积的比例、遮罩颜色、刮开后的回调接口,并将刮刮卡的底图和Bitmap加载到ScratchCardView中。在onScratchComplete()方法中,我们使用了Toast来显示“刮开了一半”的信息。
以上两个示例展示了如何使用ScratchCardView实现自定义的刮刮卡效果。需要注意的是,ScratchCardView在使用之前需要先调用init()方法进行初始化。
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