一、创建悬浮图标类

package com.test.androidtest;

import android.content.Context;
import android.graphics.PixelFormat;
import android.util.Log;
import android.view.Gravity;
import android.view.MotionEvent;
import android.view.View;
import android.view.WindowManager;
import android.widget.ImageView;

/**
 * 悬浮图标
 */
public class GameFloatView extends ImageView {

	private static GameFloatView instance;
	
	private WindowManager wm;
	private WindowManager.LayoutParams wmParams;
	
	private float mTouchStartX;
	private float mTouchStartY;
	private float mRawX;
	private float mRawY;
	
	public GameFloatView(Context context) {
		super(context);
		createFloat(context);
	}
	
	private void createFloat(Context context)
	{
		wm = (WindowManager)(context.getSystemService(Context.WINDOW_SERVICE));
		wmParams = new WindowManager.LayoutParams();
		//wmParams.type = WindowManager.LayoutParams.TYPE_TOAST;//设置窗口类型
		wmParams.format = PixelFormat.RGBA_8888;//设置背景透明
		wmParams.flags = WindowManager.LayoutParams.FLAG_NOT_TOUCH_MODAL|WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE;
		wmParams.gravity = Gravity.LEFT|Gravity.TOP;   //设置屏幕坐标系的原点在左上角
		//设置坐标(屏幕左上角)
		wmParams.x = 0;
		wmParams.y = 0;
		//设置宽高
		wmParams.width = WindowManager.LayoutParams.WRAP_CONTENT;
		wmParams.height = WindowManager.LayoutParams.WRAP_CONTENT;
		wm.addView(this, wmParams);//显示悬浮图标
		this.setImageResource(R.drawable.game_float_view_bg);
		//处理拖动
		this.setOnTouchListener(new OnTouchListener(){
			@Override
			public boolean onTouch(View v, MotionEvent event) {
				//获取屏蔽坐标(以屏幕左上角为原点)
				mRawX = event.getRawX();
				mRawY = event.getRawY();
				
				switch(event.getAction()){
					case MotionEvent.ACTION_DOWN:
						//获取相对view的坐标(以此view左上角为原点)
						mTouchStartX = event.getX();
						mTouchStartY = event.getY();
						break;
					case MotionEvent.ACTION_MOVE:
						updatePosition();
						break;
					case MotionEvent.ACTION_UP:
						updatePosition();
						mTouchStartX=mTouchStartY=0;
						break;
				}
				return false;
			}
		});
		//处理Click
		this.setOnClickListener(new OnClickListener(){
			@Override
			public void onClick(View v) {
				Log.i("test", "点击悬浮图标 onClick");
			}
		});
	}

	void updatePosition()
	{
		//在全屏模式(Fullscreen)下以下计算方式是对的。如果有状态栏，需要减去状态栏高度。
		wmParams.x=(int)(mRawX-mTouchStartX);
		wmParams.y=(int)(mRawY-mTouchStartY);
		wm.updateViewLayout(this, wmParams);
	}
	
	public static void show(Context context)
	{
		if(instance == null)
			instance = new GameFloatView(context);
		instance.setVisibility(VISIBLE);
	}
	
	public static void hide()
	{
		if(instance != null)
			instance.setVisibility(GONE);
	}
	
	public void onDestroy()
	{
		wm.removeView(this);
	}
	
	public static void destroy()
	{
		if(instance != null){
			instance.onDestroy();
			instance = null;
		}
	}
}

二、创建活动

package com.test.androidtest;

import android.app.Activity;
import android.os.Bundle;

public class GameFloatActivity extends Activity{
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.fragment_main);
	}
	
	@Override
	protected void onResume(){
		super.onResume();
		GameFloatView.show(this);
	}
	
	@Override
	protected void onPause(){
		super.onPause();
		GameFloatView.hide();
	}
	
	@Override
	protected void onDestroy(){
		super.onDestroy();
		GameFloatView.destroy();
	}
}

运行测试