Android实现图片拖动效果

xmlns:tools="http://schemas.and***roid.com/tools"

android:layout_width="match_parent"

android:layout_height="match_parent">

android:id="@+id/iv_main"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:src="@drawable/test"/>

publicclassMainActivityextendsActivityimplementsOnTouchListener {

privateImageView iv_main;

privateRelativeLayout parentView;

@Override

protectedvoidonCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

iv_main = (ImageView) findViewById(R.id.iv_main);

parentView = (RelativeLayout) iv_main.getParent();

/*

int right = parentView.getRight(); //0

int bottom = parentView.getBottom(); //0

Toast.makeText(this, right+"---"+bottom, 1).show();

*/

//设置touch监听

iv_main.setOnTouchListener(this);

}

privateintlastX;

privateintlastY;

privateintmaxRight;

privateintmaxBottom;

@Override

publicbooleanonTouch(View v, MotionEvent event) {

//得到事件的坐标

inteventX = (int) event.getRawX();

inteventY = (int) event.getRawY();

switch(event.getAction()) {

caseMotionEvent.ACTION_DOWN:

//得到父视图的right/bottom

if(maxRight==0) {//保证只赋一次值

maxRight = parentView.getRight();

maxBottom = parentView.getBottom();

}

//第一次记录lastX/lastY

lastX =eventX;

lastY = eventY;

break;

caseMotionEvent.ACTION_MOVE:

//计算事件的偏移

intdx = eventX-lastX;

intdy = eventY-lastY;

//根据事件的偏移来移动imageView

intleft = iv_main.getLeft()+dx;

inttop = iv_main.getTop()+dy;

intright = iv_main.getRight()+dx;

intbottom = iv_main.getBottom()+dy;

//限制left >=0

if(left

right += -left;

left =0;

}

//限制top

if(top

bottom += -top;

top =0;

}

//限制right

if(right>maxRight) {

left -= right-maxRight;

right = maxRight;

}

//限制bottom

if(bottom>maxBottom) {

top -= bottom-maxBottom;

bottom = maxBottom;

}

iv_main.layout(left, top, right, bottom);

//再次记录lastX/lastY

lastX = eventX;

lastY = eventY;

break;

default:

break;

}

returntrue;//所有的motionEvent都交给imageView处理

}

}