本篇内容主要讲解“Android怎么实现可随意拖动的View效果”，感兴趣的朋友不妨来看看。本文介绍的方法操作简单快捷，实用性强。下面就让小编来带大家学习“Android怎么实现可随意拖动的View效果”吧!
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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：
