第一篇简书的文章，记录下我的学习情况吧，目前想学习下android的拖拽的实现，因为支付宝之前的首页是支持拖动的，而且实现非常好看，我就想实现支付宝的控件拖动，后来支付宝更新之后改成添加了，这个demo我也实现了，所以现在学习一下android的拖拽，现在网上找个例子。
public classDraftDemoextendsAppCompatActivityimplementsView.OnTouchListener {
ImageView image;
int X,Y;
int screenWidth,screenHeight;
ActionBar actionbar;
@Override
protected void onCreate(@NullableBundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.draft);
image= (ImageView) findViewById(R.id.image);
if(image!=null) {
image.setOnTouchListener(this);
}
actionbar= getSupportActionBar();
Display dis =this.getWindowManager().getDefaultDisplay();
screenWidth= dis.getWidth();
screenHeight= dis.getHeight();
}
@Override
public booleanonTouch(View v,MotionEvent event) {
switch(event.getAction()) {
caseMotionEvent.ACTION_DOWN:
X= (int) event.getRawX();
Y= (int) event.getRawY();
break;
caseMotionEvent.ACTION_MOVE:
int dx = (int) event.getRawX() -X;
int dy = (int) event.getRawY() -Y;
int top = v.getTop() + dy;
int left = v.getLeft() + dx;
if(top <=0) {
top =0;
}
if(actionbar!=null){//判断是否超出屏幕范围
if(top >=screenHeight-image.getHeight()-actionbar.getHeight()-getStatusBarHeight()) {
top =screenHeight-image.getHeight()-actionbar.getHeight()-getStatusBarHeight();
}
}else{
if(top >=screenHeight-image.getHeight()-getStatusBarHeight()) {
top =screenHeight-image.getHeight()-getStatusBarHeight();
}
}
if(left >=screenWidth-image.getWidth()) {
left =screenWidth-image.getWidth();
}
if(left <=0) {
left =0;
}
v.layout(left,top,left +image.getWidth(),top +image.getHeight());
X= (int) event.getRawX();
Y= (int) event.getRawY();
break;
caseMotionEvent.ACTION_UP:
break;
}
return false;
}
private intgetStatusBarHeight() {
Class c =null;
Object obj =null;
Field field =null;
intx =0,sbar =0;
try{
c = Class.forName("com.android.internal.R$dimen");
obj = c.newInstance();
field = c.getField("status_bar_height");
x = Integer.parseInt(field.get(obj).toString());
sbar =this.getResources().getDimensionPixelSize(x);
}catch(Exception e1) {
e1.printStackTrace();
}
returnsbar;
}
｝
上面这段代码是根据链接的源代码修改得来，源代码没有解决有actionbar时的高度检测不正确的问题，intgetStatusBarHeight()该函数是返回手机状态栏的高度，加上actionbar完美解决。
解释：getTop();是获取子View左上角距父View顶部的距离，getLeft();是获取子View左上角距父View左侧的距离；event.getX();event.getY();是触摸点相对于其所在组件坐标系的坐标event.getRawX();event.getRawY();是触摸点相对于屏幕默认坐标系的坐标。详情请看这边
这篇就简单说明这些。至于事件分发以后再更。
