android 图片放大缩小

package com.leo.lsn7; import android.animation.ObjectAnimator; import android.content.Context; import android.graphics.Bitmap; import android.graphics.BitmapFactory; import android.graphics.Canvas; import android.graphics.Paint; import android.util.AttributeSet; import android.view.GestureDetector; import android.view.MotionEvent; import android.view.ScaleGestureDetector; import android.view.View; import android.widget.OverScroller; import androidx.annotation.Nullable; public class PhotoView extends View { private Bitmap bitmap; private Paint paint; // 偏移值 private float originalOffsetX; private float originalOffsetY; // 一边全屏，一边留白 private float smallScale; // 一边全屏，一边超出屏幕 private float bigScale; private float OVER_SCALE_FACTOR = 1.5f; private float currentScale; private boolean isEnlarge; private GestureDetector gestureDetector; private float offsetX; private float offsetY; private OverScroller overScroller; private FlingRunner flingRunner; private ScaleGestureDetector scaleGestureDetector; private boolean isScale; public PhotoView(Context context) { this(context, null); } public PhotoView(Context context, @Nullable AttributeSet attrs) { this(context, attrs, 0); } public PhotoView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) { super(context, attrs, defStyleAttr); init(context); } private void init(Context context) { // 获取bitmap对象 bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.photo); paint = new Paint(); gestureDetector = new GestureDetector(context, new PhotoGestureListener()); overScroller = new OverScroller(context); flingRunner = new FlingRunner(); scaleGestureDetector = new ScaleGestureDetector(context, new PhotoScaleGestureListener()); } @Override public boolean onTouchEvent(MotionEvent event) { // 双指操作优先 boolean result = scaleGestureDetector.onTouchEvent(event); if (!scaleGestureDetector.isInProgress()) { result = gestureDetector.onTouchEvent(event); } return result; } @Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); float scaleFraction = (currentScale - smallScale) / (bigScale - smallScale); canvas.translate(offsetX * scaleFraction, offsetY * scaleFraction); // smallScale --》 bigScale canvas.scale(currentScale, currentScale, getWidth() / 2f, getHeight() / 2f); // 绘制bitmap canvas.drawBitmap(bitmap, originalOffsetX, originalOffsetY, paint); } // onMeasure --> onSizeChanged // 每次改变尺寸时也会调用 @Override protected void onSizeChanged(int w, int h, int oldw, int oldh) { super.onSizeChanged(w, h, oldw, oldh); // 需要得到 浮点数，否则会留条小缝 originalOffsetX = (getWidth() - bitmap.getWidth()) / 2f; originalOffsetY = (getHeight() - bitmap.getHeight()) / 2f; // 图片是横向的 if ((float) bitmap.getWidth() / bitmap.getHeight() > (float) getWidth() / getHeight()) { smallScale = (float) getWidth() / bitmap.getWidth(); bigScale = (float) getHeight() / bitmap.getHeight() * OVER_SCALE_FACTOR; } else { // 纵向的图片 smallScale = (float) getHeight() / bitmap.getHeight(); bigScale = (float) getWidth() / bitmap.getWidth() * OVER_SCALE_FACTOR; } currentScale = smallScale; } class PhotoGestureListener extends GestureDetector.SimpleOnGestureListener { // Up时触发 双击的时候，触发两次？？第二次抬起时触发 @Override public boolean onSingleTapUp(MotionEvent e) { return super.onSingleTapUp(e); } // 长按 -- 300ms @Override public void onLongPress(MotionEvent e) { super.onLongPress(e); } /** * 类似move事件 * * @param e1 * @param e2 * @param distanceX 在 X 轴上滑过的距离（单位时间） 旧位置 - 新位置 * @param distanceY * @return */ @Override public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) { // 只有在放大的情况下，才能进行移动 if (isEnlarge) { offsetX -= distanceX; offsetY -= distanceY; fixOffsets(); invalidate(); } return super.onScroll(e1, e2, distanceX, distanceY); } // 抛掷 @Override public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) { if (isEnlarge) { // 只会处理一次 overScroller.fling((int) offsetX, (int) offsetY, (int) velocityX, (int) velocityY, -(int) (bitmap.getWidth() * bigScale - getWidth()) / 2, (int) (bitmap.getWidth() * bigScale - getWidth()) / 2, -(int) (bitmap.getHeight() * bigScale - getHeight()) / 2, (int) (bitmap.getHeight() * bigScale - getHeight()) / 2, 600, 600); postOnAnimation(flingRunner); } return super.onFling(e1, e2, velocityX, velocityY); } // 延时触发 100ms -- 点击效果，水波纹 @Override public void onShowPress(MotionEvent e) { super.onShowPress(e); } // 按下 -- 注意：直接返回true @Override public boolean onDown(MotionEvent e) { return true; } // 双击 -- 第二次点击按下的时候 -- 40ms（小于表示：防抖动） -- 300ms @Override public boolean onDoubleTap(MotionEvent e) { isEnlarge = !isEnlarge; if (isEnlarge) { offsetX = (e.getX() - getWidth() / 2f) - (e.getX() - getWidth() / 2) * bigScale / smallScale; offsetY = (e.getY() - getHeight() / 2f) - (e.getY() - getHeight() / 2) * bigScale / smallScale; fixOffsets(); // 启动属性动画 getScaleAnimator().start(); } else { getScaleAnimator().reverse(); } // invalidate(); return super.onDoubleTap(e); } // 双击第二次 down、move、up都会触发 @Override public boolean onDoubleTapEvent(MotionEvent e) { return super.onDoubleTapEvent(e); } // 单击按下时触发，双击时不触发， // 延时300ms触发TAP事件 @Override public boolean onSingleTapConfirmed(MotionEvent e) { return super.onSingleTapConfirmed(e); } } class FlingRunner implements Runnable { @Override public void run() { // 动画还在执行 则返回true if (overScroller.computeScrollOffset()) { offsetX = overScroller.getCurrX(); offsetY = overScroller.getCurrY(); invalidate(); // 没帧动画执行一次，性能更好 postOnAnimation(this); } } } private void fixOffsets() { offsetX = Math.min(offsetX, (bitmap.getWidth() * bigScale - getWidth()) / 2); offsetX = Math.max(offsetX, -(bitmap.getWidth() * bigScale - getWidth()) / 2); offsetY = Math.min(offsetY, (bitmap.getHeight() * bigScale - getHeight()) / 2); offsetY = Math.max(offsetY, -(bitmap.getHeight() * bigScale - getHeight()) / 2); } /** * 属性动画，设置放大缩小的效果 */ private ObjectAnimator scaleAnimator;