android 图片的 放大 缩小 移动

jopen 11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);                }                        }