Android使用Canvas对象实现刮刮乐效果

Android使用Canvas对象实现刮刮乐效果攻略

简介

在Android应用中实现刮刮乐效果可以增加用户的互动性和乐趣。本攻略将详细介绍如何使用Canvas对象来实现刮刮乐效果，并提供两个示例说明。

步骤

步骤一：创建布局文件

首先，我们需要创建一个布局文件来显示刮刮乐效果。在XML布局文件中添加一个SurfaceView元素，用于绘制刮刮乐效果。

<RelativeLayout xmlns:android=\"http://schemas.android.com/apk/res/android\"
    xmlns:tools=\"http://schemas.android.com/tools\"
    android:layout_width=\"match_parent\"
    android:layout_height=\"match_parent\">

    <SurfaceView
        android:id=\"@+id/scratch_view\"
        android:layout_width=\"match_parent\"
        android:layout_height=\"match_parent\" />

</RelativeLayout>

步骤二：创建自定义View

接下来，我们需要创建一个自定义的View类，用于处理刮刮乐效果的绘制和触摸事件。

public class ScratchView extends SurfaceView implements SurfaceHolder.Callback {

    private SurfaceHolder surfaceHolder;
    private Paint paint;
    private Path path;

    public ScratchView(Context context) {
        super(context);
        init();
    }

    public ScratchView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    private void init() {
        surfaceHolder = getHolder();
        surfaceHolder.addCallback(this);

        paint = new Paint();
        paint.setAntiAlias(true);
        paint.setStyle(Paint.Style.STROKE);
        paint.setStrokeWidth(50);
        paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));

        path = new Path();
    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        // 在Surface创建时开始绘制
        draw();
    }

    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
        // Surface尺寸改变时重新绘制
        draw();
    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        // Surface销毁时停止绘制
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        // 处理触摸事件，实现刮刮乐效果
        float x = event.getX();
        float y = event.getY();

        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                path.moveTo(x, y);
                break;
            case MotionEvent.ACTION_MOVE:
                path.lineTo(x, y);
                draw();
                break;
            case MotionEvent.ACTION_UP:
                break;
        }

        return true;
    }

    private void draw() {
        Canvas canvas = surfaceHolder.lockCanvas();
        if (canvas != null) {
            canvas.drawColor(Color.WHITE);
            canvas.drawPath(path, paint);
            surfaceHolder.unlockCanvasAndPost(canvas);
        }
    }
}

步骤三：在Activity中使用自定义View

最后，我们需要在Activity中使用自定义的View来显示刮刮乐效果。

public class MainActivity extends AppCompatActivity {

    private ScratchView scratchView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        scratchView = findViewById(R.id.scratch_view);
    }
}

示例说明

示例一：刮刮乐涂层

在这个示例中，我们将在刮刮乐涂层上绘制一个图片，并实现刮刮乐效果。

public class ScratchView extends SurfaceView implements SurfaceHolder.Callback {

    // ...

    private Bitmap scratchLayer;

    public ScratchView(Context context) {
        super(context);
        init();
    }

    public ScratchView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    private void init() {
        // ...

        scratchLayer = BitmapFactory.decodeResource(getResources(), R.drawable.scratch_layer);
    }

    private void draw() {
        Canvas canvas = surfaceHolder.lockCanvas();
        if (canvas != null) {
            canvas.drawColor(Color.WHITE);
            canvas.drawBitmap(scratchLayer, 0, 0, null);
            canvas.drawPath(path, paint);
            surfaceHolder.unlockCanvasAndPost(canvas);
        }
    }
}

示例二：刮刮乐奖品

在这个示例中，我们将在刮刮乐涂层上绘制一个奖品，并实现刮刮乐效果。

public class ScratchView extends SurfaceView implements SurfaceHolder.Callback {

    // ...

    private Bitmap prizeImage;

    public ScratchView(Context context) {
        super(context);
        init();
    }

    public ScratchView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    private void init() {
        // ...

        prizeImage = BitmapFactory.decodeResource(getResources(), R.drawable.prize_image);
    }

    private void draw() {
        Canvas canvas = surfaceHolder.lockCanvas();
        if (canvas != null) {
            canvas.drawColor(Color.WHITE);
            canvas.drawBitmap(prizeImage, 0, 0, null);
            canvas.drawPath(path, paint);
            surfaceHolder.unlockCanvasAndPost(canvas);
        }
    }
}

以上就是使用Canvas对象实现刮刮乐效果的完整攻略，希望对你有帮助！