android 图片的 放大 缩小 移动
jopen
10年前
public class MainActivity extends Activity { private ImageView imageView; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); imageView = (ImageView) findViewById(R.id.imageView); imageView.setOnTouchListener(new OnTouchListener() { // 设置开始点 private PointF startPoint = new PointF(); // 设置图片位置的变换矩阵 private Matrix matrix = new Matrix(); // 设置图片当前位置的变换矩阵 private Matrix currentMatrix = new Matrix(); // 初始化模式参数 private int mode = 0; // 无模式 private static final int NONE = 0; // 拖拉模式 private static final int DRAG = 1; // 缩放模式 private static final int ZOOM = 2; // 开启缩放效果的门槛 private static final float ZOOM_THRESHOLD = 10.0f; // 开始距离 private float startDistance; // 中心点 private PointF middlePoint; @Override public boolean onTouch(View v, MotionEvent event) { switch (event.getAction() & MotionEvent.ACTION_MASK) { case MotionEvent.ACTION_DOWN: mode = DRAG; // 记录图片当前的移动位置 currentMatrix.set(imageView.getImageMatrix()); // 记录开始坐标 startPoint.set(event.getX(), event.getY()); break; // 当屏幕上已经有触点（手指），再有手指按下时触发该事件 case MotionEvent.ACTION_POINTER_DOWN: mode = ZOOM; //得到两点间的距离 startDistance = getDistance(event); //如果大于 if(startDistance > ZOOM_THRESHOLD) { //得到两点的中间点 middlePoint = getMiddlePoint(event); // 记录图片当前的缩放比例 currentMatrix.set(imageView.getImageMatrix()); } break; case MotionEvent.ACTION_MOVE: if(mode == DRAG) { // 获取X轴移动距离 float distanceX = event.getX() - startPoint.x; // 获取Y轴移动距离 float distanceY = event.getY() - startPoint.y; // 在上次移动停止位置的基础上再进行移动 matrix.set(currentMatrix); // 实现图片位置移动 matrix.postTranslate(distanceX, distanceY); }else if(mode == ZOOM) { // 结束距离 float endDistance = getDistance(event); if(endDistance > ZOOM_THRESHOLD) { // 缩放比例 float scale = endDistance / startDistance; matrix.set(currentMatrix); matrix.postScale(scale, scale, middlePoint.x, middlePoint.y); } } break; case MotionEvent.ACTION_UP: // 当手指离开屏幕，但屏幕上仍有其他触点（手指）时触发该事件 case MotionEvent.ACTION_POINTER_UP: mode = 0; break; } imageView.setImageMatrix(matrix); return true; } }); } /** * 计算两点之间的距离 */ public static float getDistance(MotionEvent event) { //第二个点x、y坐标减去第一个点x、y坐标 float disX = event.getX(1) - event.getX(0); float disY = event.getY(1) - event.getY(0); return FloatMath.sqrt(disX * disX + disY * disY); } /** * 计算两点之间的中间点 */ public static PointF getMiddlePoint(MotionEvent event) { float midX = (event.getX(0) + event.getX(1)) /2; float midY = (event.getY(0) + event.getY(1)) /2; return new PointF(midX, midY); } }