启动前台Activity

<uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW"/>

<permission android:name="android.permission.SYSTEM_ALERT_WINDOW"
        android:label="@string/permlab_systemAlertWindow"
        android:description="@string/permdesc_systemAlertWindow"
        android:protectionLevel="signature|preinstalled|appop|pre23|development" />

public static boolean checkFloatPermission(Context context) {
        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.KITKAT)//4.4-5.1
            return true;
        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.M) {//6.0
            try {
                Class cls = Class.forName("android.content.Context");
                Field declaredField = cls.getDeclaredField("APP_OPS_SERVICE");
                declaredField.setAccessible(true);
                Object obj = declaredField.get(cls);
                if (!(obj instanceof String)) {
                    return false;
                }
                String str2 = (String) obj;
                obj = cls.getMethod("getSystemService", String.class).invoke(context, str2);
                cls = Class.forName("android.app.AppOpsManager");
                Field declaredField2 = cls.getDeclaredField("MODE_ALLOWED");
                declaredField2.setAccessible(true);
                Method checkOp = cls.getMethod("checkOp", Integer.TYPE, Integer.TYPE, String.class);
                int result = (Integer) checkOp.invoke(obj, 24, Binder.getCallingUid(), context.getPackageName());
                return result == declaredField2.getInt(cls);
            } catch (Exception e) {
                return false;
            }
        } else {
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {//8
                AppOpsManager appOpsMgr = (AppOpsManager) context.getSystemService(Context.APP_OPS_SERVICE);
                if (appOpsMgr == null)
                    return false;
                int mode = appOpsMgr.checkOpNoThrow("android:system_alert_window", android.os.Process.myUid(), context
                        .getPackageName());
                return Settings.canDrawOverlays(context) || mode == AppOpsManager.MODE_ALLOWED || mode == AppOpsManager.MODE_IGNORED;
            } else {
                return Settings.canDrawOverlays(context);
            }
        }
    }

if(!(checkFloatPermission(this))){
            Toast.makeText(getApplicationContext(),"请给软件设置悬浮窗权限，否则无法正常使用！",Toast.LENGTH_SHORT).show();
            Intent intent = new Intent(Settings.ACTION_MANAGE_OVERLAY_PERMISSION);
            startActivity(intent);
        }

Intent intent1 = new Intent(getApplicationContext(), MainActivity.class);
        intent1.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
        getApplicationContext().startActivity(intent1);