Android实现随意拖动View效果的实例代码

项目过程中要实现能在页面中随意的拖动，刚开始实现是用悬浮球的形式进行实现，因为之前项目中用过，实现后发现用户每次安装后，都有权限的限制，甚至有些用户关闭悬浮球权限之后，不知道怎么在手机上打开悬浮球的权限，这样的话用户体验很不好，所以自己重新自定义实现在页面中拖动，不需要请求权限。

自定义随意拖动view：

package com.dragdemo;
import android.annotation.suppresslint;
import android.content.context;
import android.util.attributeset;
import android.util.log;
import android.view.motionevent;
import android.widget.imageview;
/**
 *随意拖动的view
 */
@suppresslint("appcompatcustomview")
public class dragview extends imageview {
  private int width;
  private int height;
  private int screenwidth;
  private int screenheight;
  private context context;
  //是否拖动
  private boolean isdrag=false;
  public boolean isdrag() {
    return isdrag;
  }
  public dragview(context context, attributeset attrs) {
    super(context, attrs);
    this.context=context;
  }
  @override
  protected void onmeasure(int widthmeasurespec, int heightmeasurespec) {
    super.onmeasure(widthmeasurespec, heightmeasurespec);
    width=getmeasuredwidth();
    height=getmeasuredheight();
    screenwidth= screenutil.getscreenwidth(context);
    screenheight=screenutil.getscreenheight(context)-getstatusbarheight();
  }
  public int getstatusbarheight(){
    int resourceid = getresources().getidentifier("status_bar_height", "dimen", "android");
    return getresources().getdimensionpixelsize(resourceid);
  }
  private float downx;
  private float downy;
  @override
  public boolean ontouchevent(motionevent event) {
    super.ontouchevent(event);
    if (this.isenabled()) {
      switch (event.getaction()) {
        case motionevent.action_down:
          isdrag=false;
          downx = event.getx();
          downy = event.gety();
          break;
        case motionevent.action_move:
          log.e("kid","action_move");
          final float xdistance = event.getx() - downx;
          final float ydistance = event.gety() - downy;
          int l,r,t,b;
          //当水平或者垂直滑动距离大于10,才算拖动事件
          if (math.abs(xdistance) >10 ||math.abs(ydistance)>10) {
            log.e("kid","drag");
            isdrag=true;
             l = (int) (getleft() + xdistance);
             r = l+width;
             t = (int) (gettop() + ydistance);
             b = t+height;
            //不划出边界判断,此处应按照项目实际情况,因为本项目需求移动的位置是手机全屏,
            // 所以才能这么写,如果是固定区域,要得到父控件的宽高位置后再做处理
            if(l<0){
              l=0;
              r=l+width;
            }else if(r>screenwidth){
              r=screenwidth;
              l=r-width;
            }
            if(t<0){
              t=0;
              b=t+height;
            }else if(b>screenheight){
              b=screenheight;
              t=b-height;
            }
            this.layout(l, t, r, b);
          }
          break;
        case motionevent.action_up:
          setpressed(false);
          break;
        case motionevent.action_cancel:
          setpressed(false);
          break;
      }
      return true;
    }
    return false;
  }
}

用到的工具类：

package com.dragdemo;
import android.content.context;
import android.util.displaymetrics;
import android.view.display;
import android.view.view;
import android.view.windowmanager;
public class screenutil {
  private static int width = 0;
  private static int height = 0;
  private static int showheight = 0;
  private static int statusheight = 0;
  private static float density = 0;
  public static int getscreenwidth(context context) {
    if (width == 0) {
      windowmanager manager = (windowmanager) context
          .getsystemservice(context.window_service);
      display display = manager.getdefaultdisplay();
      width = display.getwidth();
    }
    return width;
  }
  public static int getscreenheight(context context) {
    if (height == 0) {
      windowmanager manager = (windowmanager) context
          .getsystemservice(context.window_service);
      display display = manager.getdefaultdisplay();
      height = display.getheight();
    }
    return height;
  }
  public static int getscreenshowheight(context context) {
    if (showheight == 0) {
      showheight = getscreenheight(context) - getstatusbarheight(context);
    }
    return showheight;
  }
  public static int getstatusbarheight(context context) {
    if (statusheight > 0) {
      return statusheight;
    }
    class<?> c = null;
    object obj = null;
    java.lang.reflect.field field = null;
    int x = 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());
      statusheight = context.getresources().getdimensionpixelsize(x);
      return statusheight;
    } catch (throwable e) {
      e.printstacktrace();
    }
    return statusheight;
  }
  public static float getscreendensity(context context) {
    if (density == 0) {
      try {
        displaymetrics dm = new displaymetrics();
        windowmanager manager = (windowmanager) context
            .getsystemservice(context.window_service);
        manager.getdefaultdisplay().getmetrics(dm);
        density = dm.density;
      } catch (exception ex) {
        ex.printstacktrace();
        density = 1.0f;
      }
    }
    return density;
  }
  public static float getscreentminlength(context context) {
    return getscreenheight(context) > getscreenwidth(context) ? getscreenwidth(context)
        : getscreenheight(context);
  }
  /**
   * 根据指定k的系数获取屏幕在max范围内的最大长宽,默认宽比较小
   * 
   * @param context
   * @param k
   * @return
   */
  public static drawwrap getcutwrap(context context, float k, float max) {
    float twidth = getscreenwidth(context);
    float theight = getscreenheight(context);
    if (twidth * max * k > theight) {
      return new drawwrap(theight * max / k, theight * max);
    } else {
      return new drawwrap(twidth * max, twidth * max * k);
    }
  }
  public static class drawwrap {
    public float width;
    public float height;
    public drawwrap(float width, float height) {
      this.width = width;
      this.height = height;
    }
  }
  public static int dip2px(context context, float dipvalue) {
    return (int) (dipvalue * getscreendensity(context) + 0.5f);
  }
  /**
   * 将sp值转换为px值，保证文字大小不变
   *
   * @param context
   * @param spvalue
   *      （displaymetrics类中属性scaleddensity）
   * @return
   */
  public static int sp2px(context context, float spvalue) {
    final float fontscale = context.getresources().getdisplaymetrics().scaleddensity;
    return (int) (spvalue * fontscale + 0.5f);
  }
  /**
   * 根据手机的分辨率从 px(像素) 的单位 转成为 dp
   */
  public static int px2dip(context context, float pxvalue) {
    final float scale = context.getresources().getdisplaymetrics().density;
    return (int) (pxvalue / scale + 0.5f);
  }
  /**
   * 获取屏幕中控件顶部位置的高度--即控件顶部的y点
   * 
   * @return
   */
  public static int getscreenviewtopheight(view view) {
    return view.gettop();
  }
  /**
   * 获取屏幕中控件底部位置的高度--即控件底部的y点
   * 
   * @return
   */
  public static int getscreenviewbottomheight(view view) {
    return view.getbottom();
  }
  /**
   * 获取屏幕中控件左侧的位置--即控件左侧的x点
   * 
   * @return
   */
  public static int getscreenviewleftheight(view view) {
    return view.getleft();
  }
  /**
   * 获取屏幕中控件右侧的位置--即控件右侧的x点
   * 
   * @return
   */
  public static int getscreenviewrightheight(view view) {
    return view.getright();
  }
  /*
   * 获取控件宽
   */
  public static int getwidth(view view) {
    int w = view.measurespec.makemeasurespec(0,
        view.measurespec.unspecified);
    int h = view.measurespec.makemeasurespec(0,
        view.measurespec.unspecified);
    view.measure(w, h);
    return (view.getmeasuredwidth());
  }
  /*
   * 获取控件高
   */
  public static int getheight(view view) {
    int w = view.measurespec.makemeasurespec(0,
        view.measurespec.unspecified);
    int h = view.measurespec.makemeasurespec(0,
        view.measurespec.unspecified);
    view.measure(w, h);
    return (view.getmeasuredheight());
  }
}

xml文件：

<com.dragdemo.dragview
    android:id="@+id/iv_drag"
    android:layout_gravity="center"
    android:src="@drawable/function_night_open"
    android:layout_width="80dp"
    android:layout_height="80dp"
    />

mainactivity:

package com.dragdemo;
import android.support.v7.app.appcompatactivity;
import android.os.bundle;
import android.view.view;
import android.widget.toast;
public class mainactivity extends appcompatactivity {
  dragview iv_drag;
  @override
  protected void oncreate(bundle savedinstancestate) {
    super.oncreate(savedinstancestate);
    setcontentview(r.layout.activity_main);
    iv_drag= (dragview) findviewbyid(r.id.iv_drag);
    iv_drag.setonclicklistener(new view.onclicklistener() {
      @override
      public void onclick(view v) {
        if(!iv_drag.isdrag()){
          toast.maketext(mainactivity.this, "响应点击", toast.length_short).show();
        }
      }
    });
  }
}

总结

以上所述是小编给大家介绍的android实现随意拖动view效果的实例代码,希望对大家有所帮助