【Android - View】之自定义View实现“刮刮卡”效果

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.PorterDuff;
import android.graphics.PorterDuffXfermode;
import android.support.annotation.Nullable;
import android.util.AttributeSet;
import android.util.TypedValue;
import android.view.MotionEvent;
import android.view.View;

/**
 * 自定义“刮刮卡”View
 */
public class GuaguakaView extends View {
    private int width, height; // 刮刮卡布局最终显示的宽度和高度

    private int foreImageRes = -1; // 自定义属性：前景图片
    private StringBuffer text = new StringBuffer(); // 自定义属性：显示的文本
    private int textSize = -1; // 自定义属性：文本字体大小
    private int textColor = Color.BLACK; // 自定义属性：文本颜色
    private float uncoverFraction = 0.6f; // 自定义属性：当刮开多少比重的时候消除所有覆盖物
    private int strokeWidth = -1; // 自定义属性：刮卡时的线条粗细

    private Canvas foreCanvas; // 前景画布，用于绘制前景色、前景图片和刮卡线条
    private Paint forePaint; // 用于绘制前景色、前景图片和刮卡线条的画笔
    private Paint textPaint; // 用于绘制文本的画笔
    private Bitmap foreBm; // 前景画布中的Bitmap对象
    private Bitmap foreImg; // 前景图片的Bitmap对象
    private Path path; // 刮卡线条
    private int[] bmPixels; // 保存前景中所有像素的数组

    private boolean isMaskCleared; // 记录前景是否都被消除了
    private float textWidth; // 文本的宽度

    private OnGuaguakaUncoverListener listener; // 回调接口

    public GuaguakaView(Context context) {
        this(context, null);
    }

    public GuaguakaView(Context context, @Nullable AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public GuaguakaView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        // 加载自定义属性
        TypedArray array = context.getTheme().obtainStyledAttributes(attrs, R.styleable.GuaguakaView, defStyleAttr, 0);
        int attrCount = array.getIndexCount();
        for (int i = 0; i < attrCount; i++) {
            int attr = array.getIndex(i);
            switch (attr) {
                case R.styleable.GuaguakaView_foreImage:
                    foreImageRes = array.getResourceId(attr, -1);
                    break;
                case R.styleable.GuaguakaView_text:
                    text.delete(0, text.length());
                    text.append(array.getString(attr));
                    break;
                case R.styleable.GuaguakaView_textSize:
                    textSize = (int) TypedValue.applyDimension(
                            TypedValue.COMPLEX_UNIT_SP,
                            array.getDimension(attr, TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_SP, 20, context.getResources().getDisplayMetrics())),
                            context.getResources().getDisplayMetrics());
                    break;
                case R.styleable.GuaguakaView_textColor:
                    textColor = array.getColor(attr, Color.BLACK);
                    break;
                case R.styleable.GuaguakaView_uncoverFraction:
                    uncoverFraction = array.getFloat(attr, 0.6f);
                    break;
                case R.styleable.GuaguakaView_strokeWidth:
                    strokeWidth = (int) TypedValue.applyDimension(
                            TypedValue.COMPLEX_UNIT_DIP,
                            array.getDimension(attr, TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 20, context.getResources().getDisplayMetrics())),
                            context.getResources().getDisplayMetrics());
                    break;
            }
        }
        array.recycle();
        // 设置一些初始值
        if (textSize == -1) {
            textSize = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_SP, 20, context.getResources().getDisplayMetrics());
        }
        if (strokeWidth == -1) {
            strokeWidth = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 20, context.getResources().getDisplayMetrics());
        }
        if (foreImageRes != -1) {
            foreImg = BitmapFactory.decodeResource(getResources(), foreImageRes);
        }
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        int widthSize = MeasureSpec.getSize(widthMeasureSpec);
        int widthMode = MeasureSpec.getMode(widthMeasureSpec);
        int heightSize = MeasureSpec.getSize(heightMeasureSpec);
        int heightMode = MeasureSpec.getMode(heightMeasureSpec);
        textPaint = new Paint();
        textPaint.setColor(textColor);
        textPaint.setTextSize(textSize);
        textWidth = textPaint.measureText(text.toString());
        // 如果设置了前景图片，则按照图片的宽高比例铺满父布局提供的宽高
        if (foreImageRes != -1) {
            int imgWidth = foreImg.getWidth();
            int imgHeight = foreImg.getHeight();
            double scale = Math.min(widthSize * 1.0 / imgWidth, heightSize * 1.0 / imgHeight);
            width = (int) (imgWidth * scale) + getPaddingLeft() + getPaddingRight();
            height = (int) (imgHeight * scale) + getPaddingTop() + getPaddingBottom();
        } else { // 如果没有设置前景图片
            width = widthMode == MeasureSpec.EXACTLY ? widthSize : (int) (textWidth + getPaddingLeft() + getPaddingRight());
            height = heightMode == MeasureSpec.EXACTLY ? heightSize : textSize + getPaddingTop() + getPaddingBottom();
        }
        setMeasuredDimension(width, height);
    }

    /**
     * 说明：正常情况下，我们不需要在继承自View的自定义View中写onLayout()方法
     * 但是由于onMeasure()方法在运行时会调用多次，因此我们把一些无关操作放到onLayout()中
     * 最终目的是避免一些操作执行多次影响整体性能
     */
    @Override
    protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
        foreBm = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
        bmPixels = new int[foreBm.getWidth() * foreBm.getHeight()];
        foreCanvas = new Canvas(foreBm);
        if (foreImageRes == -1) {
            // 如果不设置前景图片，则默认用灰色覆盖
            foreCanvas.drawColor(Color.GRAY);
        } else {
            foreImg = zoomBitmap(foreImg, width, height);
            foreCanvas.drawBitmap(foreImg, 0, 0, null);
        }
        // 准备绘制刮卡线条的画笔
        forePaint = new Paint();
        forePaint.setStyle(Paint.Style.STROKE);
        forePaint.setStrokeWidth(strokeWidth);
        forePaint.setAntiAlias(true);
        forePaint.setDither(true);
        forePaint.setStrokeCap(Paint.Cap.ROUND);
        forePaint.setStrokeJoin(Paint.Join.ROUND);
        forePaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.DST_OUT));
        path = new Path();
        super.onLayout(changed, left, top, right, bottom);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        // 绘制文本
        canvas.drawText(text.toString(), (width - textWidth) / 2, (height + textSize / 2) / 2, textPaint);
        // 绘制前景画布的Bitmap
        canvas.drawBitmap(foreBm, 0, 0, null);
        super.onDraw(canvas);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        // 如果所有覆盖物都被清除了，则不响应用户触摸事件
        if (!isMaskCleared) {
            int currX = (int) event.getX();
            int currY = (int) event.getY();
            switch (event.getAction()) {
                // 当用户按下时，将线条的前端点移动到用户按下的地方，准备绘制
                case MotionEvent.ACTION_DOWN:
                    path.moveTo(currX, currY);
                    break;
                // 当用户滑动时，将线条移动到当前位置，进行绘制
                case MotionEvent.ACTION_MOVE:
                    path.lineTo(currX, currY);
                    break;
                // 当用户抬起手指时，判断消除的面积是否达到一定的阈值，如果达到则清除所有覆盖物
                case MotionEvent.ACTION_UP:
                    int blankPx = 0;
                    foreBm.getPixels(bmPixels, 0, width, 0, 0, width, height);
                    for (int bmPixel : bmPixels) {
                        if (bmPixel == 0) {
                            blankPx++;
                        }
                    }
                    if (blankPx * 1.0 / bmPixels.length >= uncoverFraction) {
                        for (int i = 0; i < bmPixels.length; i++) {
                            bmPixels[i] = 0;
                        }
                        foreBm.setPixels(bmPixels, 0, width, 0, 0, width, height);
                        isMaskCleared = true;
                        listener.onGuaguakaUncovered(text.toString());
                    }
                    break;
            }
            // 绘制线条，请求重绘整个控件
            foreCanvas.drawPath(path, forePaint);
            invalidate();
        }
        return true;
    }

    /**
     * 设置刮刮卡View显示的文本
     */
    public void setText(String text) {
        this.text.delete(0, this.text.length());
        this.text.append(text);
    }

    /**
     * 设置刮刮卡View显示的文本的颜色
     */
    public void setTextColor(int textColor) {
        this.textColor = textColor;
    }

    /**
     * 将指定图片缩放到指定宽高，返回新的图片Bitmap对象
     */
    public static Bitmap zoomBitmap(Bitmap bm, int newWidth, int newHeight) {
        // 获得图片的宽高
        int width = bm.getWidth();
        int height = bm.getHeight();
        // 计算缩放比例
        float scaleWidth = ((float) newWidth) / width;
        float scaleHeight = ((float) newHeight) / height;
        // 取得想要缩放的matrix参数
        Matrix matrix = new Matrix();
        matrix.postScale(scaleWidth, scaleHeight);
        // 得到新的图片
        return Bitmap.createBitmap(bm, 0, 0, width, height, matrix, true);
    }

    /**
     * 刮刮卡的回调接口
     */
    interface OnGuaguakaUncoverListener {
        // 当所有覆盖物都被清除后，回调这个方法
        void onGuaguakaUncovered(String text);
    }

    /**
     * 为刮刮卡View设置Listener
     */
    public void setOnGuaguakaUncoverListener(OnGuaguakaUncoverListener listener) {
        this.listener = listener;
    }
}

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <attr name="foreImage" format="reference" />   <!-- 前景图片 -->
    <attr name="text" format="string" />           <!-- 奖励文本 -->
    <attr name="textSize" format="dimension" />    <!-- 文本字体大小 -->
    <attr name="textColor" format="color" />       <!-- 文本颜色 -->
    <attr name="uncoverFraction" format="float" /> <!-- 刮卡阈值，达到这个阈值后自动清除所有覆盖物 -->
    <attr name="strokeWidth" format="dimension" /> <!-- 刮卡线条的粗细 -->

    <declare-styleable name="GuaguakaView">
        <attr name="foreImage" />
        <attr name="text" />
        <attr name="textSize" />
        <attr name="textColor" />
        <attr name="uncoverFraction" />
        <attr name="strokeWidth" />
    </declare-styleable>
</resources>

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <my.itgungnir.custom_guaguaka.GuaguakaView
        android:id="@+id/guaguaka_main_ggk_ggk"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_centerInParent="true"
        app:foreImage="@mipmap/foreground"
        app:strokeWidth="20.0dip"
        app:textSize="20.0sp"
        app:uncoverFraction="0.6" />

</RelativeLayout>

import android.graphics.Color;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {
    private GuaguakaView ggk;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        ggk = (GuaguakaView) findViewById(R.id.guaguaka_main_ggk_ggk);

        int r = (int) (Math.random() * 10000);
        if (r != 0 && r % 2 == 0) {
            ggk.setText("$" + r);
            ggk.setTextColor(Color.RED);
        } else {
            ggk.setText("谢谢惠顾");
            ggk.setTextColor(Color.BLACK);
        }

        ggk.setOnGuaguakaUncoverListener(new GuaguakaView.OnGuaguakaUncoverListener() {
            @Override
            public void onGuaguakaUncovered(String text) {
                if ("谢谢惠顾".equals(text)) {
                    Toast.makeText(MainActivity.this, "很遗憾，没有中奖", Toast.LENGTH_SHORT).show();
                } else {
                    Toast.makeText(MainActivity.this, "恭喜！中奖" + text + "！", Toast.LENGTH_SHORT).show();
                }
            }
        });
    }
}