Android 图片拖拽、放大缩小的自定义控件
需求：像相册中的图片跟随手指拖动，双指的放大和缩小，相册中拖出范围之后有弹回的动画，感觉上很圆润，很舒服，我写的例子中并没有加动画
思路：1.自定义DragImageView.java
2.自定义中先画图片，图片大于屏幕就把图片缩小后显示，图片小于屏幕就直接显示，显示之前要计算显示图片的Rect，Rect是其实就是四个坐标，用来控制显示图片的范 围，这个Rect是根据图片的长宽比例计算而来，显示在屏幕中间。
3.跟随手指移动：在touchEvent事件中处理好单双指的各种事件之后，跟随手指就是不断的改变Rect的坐标，然后不断的invalidate()(该方法是重新强制绘制View);
4.双指缩放：双指缩放的时候从图片Rect的中心缩放的，没有实现相册那种从手指中心缩放的那种。
5.单指和双指的事件在touc事件中已近处理好了
event.getPointerCount()==2的情况就是双指部分
float X0,Y0,X1,Y1双指的四个坐标
在双指移动的时候计算一个双指的距离出来m1,在MOVE执行的时候重新计算一个新的距离m2，去判断m1和m2大小来判断双指是张开还是捏合，并且执行相应事件，判断之后把m2复制给m1，这时的MOVE事件会有新的m2出来，所以就一直判断就ok了。放大和缩小就是按照一定的比例去改变Rect的值。
DragImageView.java
public class DragImageView extends View {
private Paint mPaint;
private Drawable mDrawable;
private Rect mDrawableRect = new Rect();
// private Rect mDrawableOffsetRect = new Rect();
private Context mContext;
private float mRation_WH = 0;
private float mOldX = 0;
private float mOldY = 0;
private float mOldX0, mOldY0, mOldX1, mOldY1, mOldK, mOldB, mOldHandsX,
mOldHandsY;
private double mD1;
private boolean isFirst = true;
private int SINGALDOWN = 1;// 单点按下
private int MUTILDOWM = 2;// 双点按下
private int MUTILMOVE = 3;// 双点拖拽
private int mStatus = 0;
enum STATUS {
SINGAL, MUTILDOWN, MUTILMOVE;
}
public DragImageView(Context context) {
super(context);
this.mContext = context;
mPaint = new Paint();
mPaint.setAntiAlias(true);
mPaint.setColor(Color.BLACK);
mPaint.setStyle(Style.FILL);
mPaint.setTextSize(35.0f);
}
@SuppressLint("DrawAllocation")
@Override
protected void onDraw(Canvas canvas) {
// TODO Auto-generated method stub
super.onDraw(canvas);
if (mDrawable == null || mDrawable.getIntrinsicHeight() == 0
|| mDrawable.getIntrinsicWidth() == 0) {
return;
}
setBounds();
mDrawable.draw(canvas);
// Log.i("draw", "draw+++++++++++++++++++++++++++++++++++++++");
}
@SuppressLint("ClickableViewAccessibility")
@Override
public boolean onTouchEvent(MotionEvent event) {
// TODO Auto-generated method stub
switch (event.getPointerCount()) {
case 1:
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
mStatus = SINGALDOWN;
mOldX = event.getX();
mOldY = event.getY();
// Log.i("x_y_down", event.getX() + "__" + event.getY());
break;
case MotionEvent.ACTION_UP:
checkBounds();
// Log.i("x_y_up", event.getX() + "__" + event.getY());
break;
case MotionEvent.ACTION_MOVE:
// Log.i("x_y_move", event.getX() + "__" + event.getY());
if (mStatus == SINGALDOWN) {
int offsetWidth = (int) (event.getX() - mOldX);
int offsetHeight = (int) (event.getY() - mOldY);
// Log.i("x_y_offset", offsetWidth + "__" + offsetHeight);
mOldX = event.getX();
mOldY = event.getY();
mDrawableRect.offset(offsetWidth, offsetHeight);
invalidate();
}
break;
default:
break;
}
break;
default:
/*
* mStatus = MUTILDOWM; if (mStatus == MUTILDOWM) { mOldX0 =
* event.getX(0); mOldY0 = event.getY(0); mOldX1 = event.getX(1);
* mOldY1 = event.getY(1); mOldK = (mOldY1 - mOldY0) / (mOldX1 -
* mOldX0); mOldB = (mOldY0 * mOldX1 - mOldY1 * mOldX0) / (mOldX1 -
* mOldX0); mOldHandsX = (mOldX0 + mOldX1) / 2; mOldHandsY =
* mOldHandsX * mOldK + mOldB; mD1 = Math.sqrt(Math.pow(mOldX0 -
* mOldX1, 2) + Math.pow(mOldY0 - mOldY1, 2)); Log.i("mD1", mD1 +
* "________________"); }
*/
switch (event.getAction()) {
case MotionEvent.ACTION_POINTER_DOWN:
Log.i("DOUBLETOWDOWN", "true");
break;
case MotionEvent.ACTION_MOVE:
// Log.i("x_y_move", event.getX(0) + "__" + event.getY(0) +
// "___"
// + event.getX(1) + "__" + event.getY(1));
mStatus = MUTILMOVE;
float X0 = event.getX(0);
float Y0 = event.getY(0);
float X1 = event.getX(1);
float Y1 = event.getY(1);
float k = (Y1 - Y0) / (X1 - X0);
float b = (Y0 * X1 - Y1 * X0) / (X1 - X0);
int RectCenterX = mDrawableRect.centerX();
int RectCenterY = mDrawableRect.centerY();
float mHandsX = (X0 + X1) / 2;
float mHandsY = mHandsX * k + b;
double mD2 = Math.sqrt(Math.pow(X0 - X1, 2)
+ Math.pow(Y0 - Y1, 2));
Log.i("GCM", mD2 + "________________X:" + mHandsX + "___Y:"
+ mHandsY);
if (mD1 < mD2) {