安卓自定义悬浮按钮实现

以下：内容没有参考，写的也是一个比较简单的例子，主要就是应用切换前后台时会显示/隐藏悬浮窗。内容仅用于自我记录学习使用。

项目的开发时应用在登陆后显示一个悬浮窗，同时显示在线人数等一些其他信息，点击悬浮按钮可以显示全局弹窗名单。开发完成后，觉着需要记录一下这种实现方式。所以写一个简单的Demo。
Demo思路是通过启动Service来添加/移除 悬浮窗，因为是一个全局悬浮窗，所以选择依附于Service。
在MyAppliction中监听应用的前后台切换来添加或者隐藏悬浮窗。
其自定义的悬浮窗View在项目中是通过Canvas手动绘制的，这里图个省事直接加载一个布局文件。主要是想理解这种添加全局悬浮窗的方式，所以Demo样式和功能能简则简。

MyAppliction

package com.example.qxb_810.floatbuttondemo.application;

import android.app.Activity;
import android.app.ActivityManager;
import android.app.Application;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.WindowManager;

import com.example.qxb_810.floatbuttondemo.service.FloatingActionService;

import java.util.List;

import static android.content.ContentValues.TAG;

/**
 * create 2018/12/1 13:31
 * desc 自定义Application
 */

public class MyApplication extends Application {
    private Intent mIntent;
    private WindowManager.LayoutParams mFloatingLayoutParams = new WindowManager.LayoutParams();

    public WindowManager.LayoutParams getmFloatingLayoutParams() {
        return mFloatingLayoutParams;
    }

    @Override
    public void onCreate() {
        super.onCreate();
        this.monitorActivityLifecycle();
    }


    /**
     * 监听程序Activity声明周期
     */
    private void monitorActivityLifecycle() {
        this.registerActivityLifecycleCallbacks(new ActivityLifecycleCallbacks() {
            @Override
            public void onActivityCreated(Activity activity, Bundle savedInstanceState) {

            }

            @Override
            public void onActivityStarted(Activity activity) {
                if (isRunningForeground()){
                    mIntent = new Intent(MyApplication.this, FloatingActionService.class);
                    startService(mIntent);
                }
            }

            @Override
            public void onActivityResumed(Activity activity) {

            }

            @Override
            public void onActivityPaused(Activity activity) {

            }

            @Override
            public void onActivityStopped(Activity activity) {
                if (!isRunningForeground()){
                    stopService(mIntent);
                }
            }

            @Override
            public void onActivitySaveInstanceState(Activity activity, Bundle outState) {

            }

            @Override
            public void onActivityDestroyed(Activity activity) {

            }
        });
    }

    /**
     * 判断应用运行在前后台
     */
    public boolean isRunningForeground() {
        ActivityManager activityManager = (ActivityManager) this.getSystemService(Context.ACTIVITY_SERVICE);
        List appProcessInfos = activityManager.getRunningAppProcesses();    // 枚举进程
        for (ActivityManager.RunningAppProcessInfo appProcessInfo : appProcessInfos) {
            if (appProcessInfo.importance == ActivityManager.RunningAppProcessInfo.IMPORTANCE_FOREGROUND) {
                if (appProcessInfo.processName.equals(this.getApplicationInfo().processName)) {
                    Log.d(TAG, "EntryActivity isRunningForeGround");
                    return true;
                }
            }
        }
        Log.d(TAG, "EntryActivity isRunningBackGround");
        return false;
    }

}

FloatingActionService.java ---- 悬浮窗所依附的Service

package com.example.qxb_810.floatbuttondemo.service;

import android.app.Service;
import android.content.Intent;
import android.graphics.PixelFormat;
import android.os.IBinder;
import android.support.annotation.Nullable;
import android.util.DisplayMetrics;
import android.view.Display;
import android.view.Gravity;
import android.view.WindowManager;
import android.widget.LinearLayout;
import android.widget.Toast;

import com.example.qxb_810.floatbuttondemo.application.MyApplication;
import com.example.qxb_810.floatbuttondemo.button.FloatingActionButton;

/**
 * create 2018/12/1 13:34
 * desc  悬浮按钮Service
 */

public class FloatingActionService extends Service {
    private WindowManager mWindowManager;
    private FloatingActionButton mButton;
    private int mScreenWidth;
    private int mScreenHeight;

    @Override
    public void onCreate() {
        super.onCreate();
        this.initView();
        this.initEvent();

    }

    @Nullable
    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        return super.onStartCommand(intent, flags, startId);
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        this.mWindowManager.removeViewImmediate(this.mButton);
    }

    /**
     * 添加按钮
     */
    private void initView() {
    	// 通过WindowManager来添加悬浮窗
        this.mWindowManager = (WindowManager) this.getApplicationContext().getSystemService(WINDOW_SERVICE);
        Display display = this.mWindowManager.getDefaultDisplay();
        DisplayMetrics metrics = new DisplayMetrics();
        display.getMetrics(metrics);
        this.mScreenWidth = metrics.widthPixels;
        this.mScreenHeight = metrics.heightPixels;

        WindowManager.LayoutParams params = ((MyApplication) this.getApplication()).getmFloatingLayoutParams();
     
       if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            mFloatingLayoutParams.type = WindowManager.LayoutParams.TYPE_APPLICATION_OVERLAY;
        } else {
            mFloatingLayoutParams.type = WindowManager.LayoutParams.TYPE_TOAST;
        }
        params.format = PixelFormat.RGBA_8888;
        params.flags = WindowManager.LayoutParams.FLAG_NOT_TOUCH_MODAL | WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE;
        params.gravity = Gravity.LEFT | Gravity.TOP;    // 左上为坐标点
        // 设置View大小
        params.height = 50;
        params.width = 50;
        // 设置View坐标位置
        params.x = 0;
        params.y = mScreenHeight / 2;

        this.mButton = FloatingActionButton.getInstance(this);
        this.mWindowManager.addView(mButton, params);
    }

    /**
     *  初始化事件
     */
    private void initEvent() {
        this.mButton.setOnClickListener(v -> {
        	// 项目中是在这里进行添加 名单弹窗 和移除名单弹窗的操作，但名单弹窗的初始化不在这里
            Toast.makeText(this, "点击了Button", Toast.LENGTH_SHORT).show();
        });
    }


}

FloatingActionButton – 弹窗按钮

package com.example.qxb_810.floatbuttondemo.button;

import android.content.Context;
import android.graphics.Canvas;
import android.support.annotation.Nullable;
import android.util.AttributeSet;
import android.view.LayoutInflater;
import android.view.MotionEvent;
import android.view.View;
import android.view.WindowManager;
import android.widget.FrameLayout;
import android.widget.LinearLayout;

import com.example.qxb_810.floatbuttondemo.R;
import com.example.qxb_810.floatbuttondemo.application.MyApplication;

import static android.content.Context.WINDOW_SERVICE;

/**
 * create 2018/12/1 13:35
 * desc 自定义悬浮按钮  --  这里随便写的一个布局文件
 */

public class FloatingActionButton extends FrameLayout {
    private Context mContext;
    private float mStartPointX;
    private float mStartPointY;
    private WindowManager mWindowManager;
    private WindowManager.LayoutParams mFloatingLayoutParams;
    private boolean isIntercept = false;
    private int mStatusHeight;

    public static FloatingActionButton getInstance(Context context) {
        FloatingActionButton button = new FloatingActionButton(context);
        return button;
    }

    public FloatingActionButton(Context context) {
        this(context, null);
    }

    public FloatingActionButton(Context context, @Nullable AttributeSet attrs) {
        this(context, attrs, -1);
    }

    public FloatingActionButton(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        mContext = context;
        initView();
    }

    @Override
    protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
        super.onLayout(changed, left, top, right, bottom);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
    }

    /**
     *  初始化View
     */
    private void initView(){
    	// 随便添加一个简单的View布局作为悬浮窗
        View view = LayoutInflater.from(mContext).inflate(R.layout.layout_floating_button, null, false);
        LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(LinearLayout.LayoutParams.WRAP_CONTENT,LinearLayout.LayoutParams.WRAP_CONTENT);
        this.addView(view, params);
        this.mWindowManager = (WindowManager) getContext().getApplicationContext().getSystemService(WINDOW_SERVICE);
        this.mFloatingLayoutParams = ((MyApplication) getContext().getApplicationContext()).getmFloatingLayoutParams();
        this.mStatusHeight = getStatusHeight(mContext);

    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        //获取相对屏幕的坐标，即以屏幕左上角为原点
        float rawX = event.getRawX();
        float rawY = event.getRawY() - mStatusHeight;   //statusHeight是系统状态栏的高度
        switch (event.getAction()){
            case MotionEvent.ACTION_DOWN:
                this.mStartPointX = event.getX();
                this.mStartPointY = event.getY();
                isIntercept = false;
                break;
            case MotionEvent.ACTION_MOVE:
                mFloatingLayoutParams.x = (int)(rawX - mStartPointX);
                mFloatingLayoutParams.y = (int)(rawY - mStartPointY);
                this.mWindowManager.updateViewLayout(this, mFloatingLayoutParams);
                isIntercept = true;
                break;
            case MotionEvent.ACTION_UP:
                mFloatingLayoutParams.x = 0;        // 这里的策略是默认松手吸附到左侧 如果需要吸附到右侧则改为mFloatingLayoutParams.x = mScreenWidth;	mScreenWidth 是屏幕宽度，不想吸附则注释这一句即可
                this.mWindowManager.updateViewLayout(this, mFloatingLayoutParams);
                break;
        }
        return isIntercept ? isIntercept : super.onTouchEvent(event);
    }

    /**
     * 状态栏的高度
     */
    public static int getStatusHeight(Context context) {
        int statusHeight = -1;
        try {
            Class clazz = Class.forName("com.android.internal.R$dimen");    //使用反射获取实例
            Object object = clazz.newInstance();
            int height = Integer.parseInt(clazz.getField("status_bar_height")
                    .get(object).toString());
            statusHeight = context.getResources().getDimensionPixelSize(height);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return statusHeight;
    }
}

布局文件