Android编程实现自定义手势的方法详解

为了实现Android自定义手势，我们需要遵循以下步骤：

1. 声明手势识别器

在Android应用中声明一个GestureDetector实例。手势识别器负责识别手势事件并将其转换为对应的回调方法。

private GestureDetector mGestureDetector = new GestureDetector(context, new GestureDetector.SimpleOnGestureListener() {
    @Override
    public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
        // 处理滑动手势事件
        return true;
    }

    @Override
    public boolean onDoubleTap(MotionEvent e) {
        // 处理双击手势事件
        return true;
    }

    // 其他手势回调方法
});

2. 重载触摸事件

将手势识别器与你的View关联，并在View中重载onTouchEvent方法，将触摸事件传递给手势识别器进行处理。

@Override
public boolean onTouchEvent(MotionEvent event) {
    mGestureDetector.onTouchEvent(event);
    return super.onTouchEvent(event);
}

3. 编写手势处理方法

根据需要编写各种手势的回调处理方法，例如滑动、双击、长按等等。

@Override
public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
    // 处理快速滑动手势
    return true;
}

@Override
public boolean onDown(MotionEvent e) {
    // 处理按下手势
    return true;
}

@Override
public void onLongPress(MotionEvent e) {
   // 处理长按手势
}

@Override
public boolean onSingleTapConfirmed(MotionEvent e) {
    // 处理单击手势
    return true;
}

@Override
public boolean onDoubleTap(MotionEvent e) {
    // 处理双击手势
    return true;
}

以下是两个关于手势动画实现的示例：

示例1：实现一个向下滑动时文字缩小，向上滑动时文字放大的效果

创建一个继承自TextView的类，在类中重载onDraw方法并在其中执行缩放操作。

public class TextZoomTextView extends TextView {
    private float mScaleFactor = 1.0f;
    private GestureDetectorCompat mGestureDetector;

    public TextZoomTextView(Context context) {
        super(context);
        mGestureDetector = new GestureDetectorCompat(context, new GestureListener());
    }

    public TextZoomTextView(Context context, AttributeSet attrs) {
        super(context, attrs);
        mGestureDetector = new GestureDetectorCompat(context, new GestureListener());
    }

    @Override
    protected void onDraw(Canvas canvas) {
        canvas.save();
        canvas.scale(mScaleFactor, mScaleFactor, getWidth() / 2f, getHeight() / 2f);
        super.onDraw(canvas);
        canvas.restore();
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        mGestureDetector.onTouchEvent(event);
        return super.onTouchEvent(event);
    }

    private class GestureListener extends GestureDetector.SimpleOnGestureListener {
        @Override
        public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
            mScaleFactor *= (1 - distanceY / getHeight());
            mScaleFactor = Math.max(0.1f, Math.min(mScaleFactor, 1f));
            invalidate();
            return true;
        }
    }
}

在你的布局文件中引用该自定义View

<com.example.TextZoomTextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Hello World!"
    android:textSize="30sp"/>

示例2：实现一个向左滑动时执行动画的效果

public class SwipeAnimationView extends View {
    private Paint mPaint;
    private RectF mRectF;
    private GestureDetectorCompat mGestureDetector;

    public SwipeAnimationView(Context context) {
        super(context);
        mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
        mPaint.setStyle(Paint.Style.FILL);
        mPaint.setColor(Color.RED);
        mRectF = new RectF();
        mGestureDetector = new GestureDetectorCompat(context, new GestureListener());
    }

    public SwipeAnimationView(Context context, AttributeSet attrs) {
        super(context, attrs);
        mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
        mPaint.setStyle(Paint.Style.FILL);
        mPaint.setColor(Color.RED);
        mRectF = new RectF();
        mGestureDetector = new GestureDetectorCompat(context, new GestureListener());
    }

    @Override
    protected void onDraw(Canvas canvas) {
        canvas.drawRoundRect(mRectF, 5, 5, mPaint);
        super.onDraw(canvas);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        mGestureDetector.onTouchEvent(event);
        return true;
    }

    private class GestureListener extends GestureDetector.SimpleOnGestureListener {
        @Override
        public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
            mRectF.left -= distanceX;
            mRectF.right -= distanceX;
            invalidate();
            return true;
        }

        @Override
        public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
            final float distance = e2.getX() - e1.getX();
            final float duration = Math.abs(velocityX) / 1000f;

            ValueAnimator animator = ValueAnimator.ofFloat(mRectF.left, mRectF.left - distance);
            animator.setInterpolator(new DecelerateInterpolator());
            animator.setDuration((long) (duration * 1000));
            animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
                @Override
                public void onAnimationUpdate(ValueAnimator animation) {
                    mRectF.left = (float) animation.getAnimatedValue();
                    mRectF.right = mRectF.left + getWidth() / 2f;
                    invalidate();
                }
            });
            animator.start();
            return true;
        }
    }
}